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A Functional Approach to the Phylogeny of the Pharyngognath Teleosts
Abstract
SYNOPSIS. Functional morphological analysis has revealed the existence of three functionally and morphologically different mechanisms underlying the tongue-parasphenoid and pharyngeal-parasphenoid bites in advanced teleost fishes. The bite is specialized differently in Pristolepis and the Anabantoidei, and in a primitive condition in both the Nandidae andChanniformes. These taxa belong to at least three unrelated lineages and do not share a commonancestry as was previously postulated. It has been possible to show how an originally primitive character can acquire a new biological and phylogenetic meaning by being integrated into a specialized functional complex. Based on functional data on the pharyngeal jaw apparatus, a new hypothesis is proposed stating that the Cichlidae, Embiotocidae, Labridae, Odacidae and Scaridae represent a monophyletic assemblage. This case study has demonstrated that reciprocal illumination of functional morphological and phylogenetic findings can lead to: (1) better tested and more precise phylogenetic hypotheses; (2) the construction of new hypotheses on the basis of specialized character complexes which were unrecognized by the use of a purely descriptive morphological approach
... Another feature supporting monophyly of the Anabantoidei has been proposed by Liem and Greenwood (1981): the unique lower pharyngeal jaw-parasphenoid bite, which is functionally separated from the swallowing mechanism. Such feeding apparatus structure seems to be supported for Anabas and Macropodus, but the occluding elements in the hyobranchial region and neurocranium remain uncertain in Nandus and Badis (Liem and Greenwood, 1981. ...
... Another feature supporting monophyly of the Anabantoidei has been proposed by Liem and Greenwood (1981): the unique lower pharyngeal jaw-parasphenoid bite, which is functionally separated from the swallowing mechanism. Such feeding apparatus structure seems to be supported for Anabas and Macropodus, but the occluding elements in the hyobranchial region and neurocranium remain uncertain in Nandus and Badis (Liem and Greenwood, 1981. Fig. 1). ...
... The hypothesis on the parasphenoid-lower pharyngeal jaw bite in the Anabantoidei is rather unusual. In the other advanced euteleosteans, the lower pharyngeal jaw (fused ceratobranchials 5) is located opposing the upper pharyngeal jaw (most often, fused pharyngobranchials 3 and 4) representing the upper-lower pharyngeal jaw bite (Liem and Greenwood, 1981;Lauder, 1982;Vandewalle et al., 2000;Berkovitz and Shellis, 2017). Thus, the biting mechanism in the Anabantoidei should be studied more thoroughly. ...
The feeding-related skull structures are described and occluding elements of the upper and lower
regions of the buccopharyngeal cavity are analyzed in climbing perch. At each side of the neurocranium, the
transverse process of the parasphenoid with four or five large conical teeth oppose the hypobranchial 3, and
the medial teeth of the parasphenoid oppose the medial joints between paired hypobranchials 3 and cerato�branchials 4. As in the majority of other advanced Teleostei, the pharyngeal bite is carried out by the lower
pharyngeal jaw (fused ceratobranchials 5) and upper pharyngeal jaws (left and right plates of pharyngobran�chials 3–4). The latter jaws are articulated with paired pharyngeal processes of the basioccipital. At both sides
of the skull, the strong elongated Baudelot’s ligament joins the basioccipital and supracleithrum. The hypoth�esis on the occurrence of the unique lower pharyngeal jaw–parasphenoid bite in climbing perch is rejec
... As currently recognized, pharyngognathy involves three prominent modifications to the typical pharyngeal jaw apparatus of percomorphs: (1) left and right lower jaw elements (fifth ceratobranchials) that are united to make a single lower pharyngeal jaw; (2) a muscular sling that directly connects the underside of the neurocranium with the lower pharyngeal jaw; and (3) a mobile diarthrotic articulation of the upper pharyngeal jaws with the neurocranium (Stiassny 1981;Stiassny and Jensen 1987;Wainwright et al. 2012). These morphological and functional features were proposed as synapomorphies uniting the Labroidei clade that included Cichlidae, Embiotocidae, Labridae, Odacidae, Scaridae, and Pomacentridae (Liem and Greenwood 1981;Kaufman and Liem 1982). In parallel to an interest in systematics, this fascinating system of pharyngeal jaws was deeply studied from a functional point of view (Liem 1973;Liem and Osse 1975). ...
... In parallel to an interest in systematics, this fascinating system of pharyngeal jaws was deeply studied from a functional point of view (Liem 1973;Liem and Osse 1975). Liem argued that the acquisition of an extra set of jaws in cichlids and other Labroidei has enabled a diversification of food preparation techniques and therefore feeding habits (Liem 1973;Liem and Osse 1975;Liem and Greenwood 1981). First, the flexibility of this highly integrated pharyngeal jaw apparatus would be a major factor that has enabled this diversity of feeding habits. ...
... In damselfishes, the characteristics of the lower pharyngeal jaw (LPJ) are a Y-shape (and width is greater than the length), no trace of a central sutural union, a well-developed median keel on the ventral face of the bone, and tooth rows arranged radially across the LPJ with teeth located over the median region of the jaw (Kaufman and Liem 1982;Stiassny and Jensen 1987). Although it is not found in all the pomacentrids (e.g., Microspathodon and Chromis), pharyngo-cleithral articulations can join the expanded lateral horns of the LPJ to the cleithrum (Liem 1973;Liem and Greenwood 1981;Stiassny and Jensen 1987). It is expected that the support provided by the articulation of the LPJ with the shoulder girdle increases the total biting force that can be exerted on prey (Galis and Snelderwaard 1997). ...
... Muscular attachment permitting occlusion and complex movements of the UPJ and LPJ jaws is a specialized adaptation that is convergent among several groups of fishes; for example, Cichlidae (Liem 1973), Scaridae (Liem and Greenwood 1981), ...
... Labridae (Liem and Greenwood 1981, Liem and Sanderson 1986, Wainwright 1988), ...
... In N. melanostomus, the direct LP and LE4 connection to the LPJ is a convergent adaptation for prey processing. In other durophagous pharyngognath fishes, the muscles are hypertrophied, particularly those primarily responsible for pharyngeal jaw occlusion (Liem and Greenwood 1981, Lauder 1982, Grubich 2000, to generate a larger force (Wainwright 1988, Galis 1992, Grubich 2000. Although the motor activity o f pharyngeal musculature was not studied (,sensu Liem 1973), differences in the mass of LP and length of PHCE and PH may indicate the primary contributing muscles in mastication. ...
The functional performance of morphological characters may change through ontogeny,
affecting the organism’s ecology. The fins and external structure of the round goby,
Neogobius melanostomus, does not change through ontogeny, but the diet changes from
soft-bodied native prey (benthic invertebrates, fish eggs, larvae) to hard-bodied zebra
mussels, Dreissena polymorpha, when the gobies reach a standard length (SL) of 60-70
mm. To feed on D. polymorpha attached to substrate via byssal fibers, N. melanostomus
uses oral jaws to remove mussels and pharyngeal jaws to process. By comparing the
performance of the oral jaw bite force through ontogeny and correlating it to the byssal
fiber attachment strength, it was concluded that smaller N. melanostomus are not capable
of primarily feeding on D. polymorpha. Examining the pharyngeal jaws, the dentition
changes with the diet shift, reflecting prey type. Morphological performance of N.
melanostomus feeding apparatus is linked to feeding ecology.
... The Pomacentroid clade of Bleeker (1877) was a member of Müller's (1843) Pharyngonathi acanthopterygii that include taxa with at least (1) united left and right lower jaw elements (fi fth ceratobranchials), (2) a muscular sling that directly connects the underside of the neurocranium with the lower pharyngeal jaw; and (3) a mobile diarthrotic articulation of the upper pharyngeal jaws with the neurocranium , Kaufman and Liem 1982. These morphological and functional characters were proposed as synapomorphies uniting an expanded Labroidei clade (Liem and Greenwood 1981) that included Cichlidae, Embiotocidae, Labridae, Odacidae and Scaridae. One year later, Kaufman and Liem (1982) added Pomacentridae to the Labroidei. ...
... In pomacentrids, the characteristics of the lower pharyngeal jaw (LPJ) are a Y-shape (and width is greater than the length), no trace of a central sutural union, a well-developed median keel on the ventral face of the bone, and tooth rows arranged radially across the LPJ with teeth located over the median region of the jaw (Kaufman andLiem 1982, Stiassny andJensen 1987). Although it is not found in all the pomacentrids (e.g., Microspathodon and Chromis), pharyngocleithral articulations can join the expanded lateral horns of the LPJ to the cleithrum (Liem 1973, Liem and Greenwood 1981, Kaufman and Liem 1982, Stiassny and Jensen 1987. Liem (1973) proposed that pharyngognathy has major implications for feeding performance because the fusion of the LPJ in a single plate allows the combination of the force exerted by right and left muscle and leads to the enhancement of force and the ability to crush hard prey . ...
... The Pomacentridae possess at least two morpho-functional novelties. (1) Similar to cichlids, labrids and embiotocids, the pomacentrids have developed modifi ed pharyngeal jaws that permit effi cient food processing (Liem and Greenwood 1981, Stiassny and Jensens 1987, Galis and Snelderwaard 1997) which could be an important functional innovation. (2) Recent morpho-functional studies demonstrated a role for the ceratomandibular ligament (c-md) during feeding and sound production . ...
Damselfishes (Pomacentridae) are highly conspicuous, diurnal inhabitants of mainly reef areas, capturing the attention of many scientists. Their high diversity and many interesting characteristics dealing with their way of life (sound production, breeding biology, sex change, farming and gregarious behavior, settlement, diet, habitat) easily explain this group is continually kept in the limelight and is the subject of numerous studies. This book gathers the data dealing with damselfish morphology, physiology, behavior, ecology and phylogeny. It contains 14 chapters written by renowned scientists.
... Whatever superficial resemblance Graus may bear to the labrids, it is just that; there are no substantive characters that would suggest a close relationship between Graus and the Labridae or related families. In recent years a considerable body of evidence has accumulated supporting the monophyly of the suborder Labroidei, comprising the Cichlidae, Embiotocidae, Pomacentridae, and Labridae (including the Scaridae and Odacidae) (Liem and Greenwood, 1981;Stiassny, 1981;Kaufman and Liem, 1982;Stiassny and Jensen, 1987). This evidence primarily involves pharyngognathy in these fishes coalescence of the fifth ceratobranchials into a single functional unit, true diarthrosis between the pharyngobranchials and the basicranium, and a suite of associated specializations involving pharyngeal muscles and bones. ...
... Although we were not able to identify specific synapomorphies in the dorsal gill arch skeletons of Graus and Girella, the overall configura-tions are very similar, the only notable differences being in the relative widths of the second and fourth infrapharyngobranchials (Fig. 3). The statement by Liem and Greenwood (1981), also mentioned by Kaufman and Liem (1982) and Stiassny and Jensen (1987) that the fifth ceratobranchials are united in Girella is erroneous; the exact source of this error has not been identified (K. Liem, pers comm). ...
... Interestingly, despite the similarity in the gill arch skeletons, there is a substantive difference in the musculature. In Graus, as in most other percoids, including scorpidids, kyphosids and the outgroup, there is a well-developed levator posterior muscle extending from the skull to the dorsal surface of the fourth epibranchial; the levator posterior is lacking in Girella (Liem and Greenwood, 1981; pers obs). ...
... The literature on osteology of labrid fishes is scattered and deals either in detail with specific structures (Kner, 1860;Prince, 1893;Delsman, 1925;Yamaoka, 1978;Van Hasselt, 1978 or is cursory, forming part of a wider study (Gregory, 1933;Ford, 1937;Clothier, 1950;Takahashi, 1962;Quignard, 1966;Nelson, 1967;McAllister, 1968: Monod, 1968Randall & Springer, 1973;Kusaka, 1974;Liem & Greenwood, 1981;Kaufman & Liem, 1982). Notable exceptions are work by Rognes (1973), Van Hasselt (1979 and Tedman (1980) on the head skeleton of various labrid genera, and unpublished studies by Gomon on the comparative osteology of Western Atlantic species of Halichoeres (Gomon, 1971) and of the labrid tribe Hypsigenyini (Gomon, 1979). ...
... (3) no subocular shelf (Regan, 1913a); (4) 3 gills (Regan, 1913a); (5) diarthrosis between the upper pharyngeal jaws and the basicranium (Yamaoka, 1978;Liem & Greenwood, 1981); (6) levator posterior muscle (LP) the dominant muscle of the lower pharyngeal jaw (Y amao ka, 1978;Liem & Greenwood, 1981) ; (7) articulation of the lower pharyngeal jaw with the cleithrum by means of a pharyngocleithral joint (Liem & Greenwood, 1981), and (8) hypertrophy of the adductor branchialis muscles (Liem & Greenwood, 1981). Liem & Greenwood (1981) additionally included the Cichlidae and Embiotocidae in the Labroidei, based on two further synapomorphies: (9) insertion of the fourth levator externus (LE4) and LP muscles on the lower pharyngeal jaw, and (10) ascending process of the premaxilla. ...
... (3) no subocular shelf (Regan, 1913a); (4) 3 gills (Regan, 1913a); (5) diarthrosis between the upper pharyngeal jaws and the basicranium (Yamaoka, 1978;Liem & Greenwood, 1981); (6) levator posterior muscle (LP) the dominant muscle of the lower pharyngeal jaw (Y amao ka, 1978;Liem & Greenwood, 1981) ; (7) articulation of the lower pharyngeal jaw with the cleithrum by means of a pharyngocleithral joint (Liem & Greenwood, 1981), and (8) hypertrophy of the adductor branchialis muscles (Liem & Greenwood, 1981). Liem & Greenwood (1981) additionally included the Cichlidae and Embiotocidae in the Labroidei, based on two further synapomorphies: (9) insertion of the fourth levator externus (LE4) and LP muscles on the lower pharyngeal jaw, and (10) ascending process of the premaxilla. ...
Six labrid genera, Austrolabrus Steindachner, Dotalabrus Whitley, Eupetrichthys Ramsay & Ogilby, Notolabrus new genus, Pictilabrus Gill, and Pseudolabrus Bleeker, are recognised as forming a monophyletic assemblage, here referred to collectively as pseudolabrines. This group comprises 23 species, including two new species described herein: Dotalabrus alleni n.sp. and Pictilabrus viridis n.sp., both from south-western Australia. The genus Suezichthys (= Suezia) Smith, previously considered closely related to Pseudolabrus, is excluded. Keys, diagnoses and descriptions of the genera and species are given. The pseudolabrines are provisionally placed in the tribe Julidini, and appear to be the plesiomorphic sister group of all other julidines. Within the pseudolabrine group, cladistic analysis supports the separation of Notolabrus n.gen., previously included with Pseudolabrus, and the inclusion of Lunolabrus Whitley as a sub genus of Pseudolabrus.
... Many elements of the pharyngeal skeleton in bony fishes bear teeth (as do palatal and neurocranial bones) which are used to hold, grasp, manipulate, transport, and process food. In some teleosts, upper and lower tooth-bearing elements of the pharyngeal arches interact to form an internal set of "pharyngeal jaws" used in elaborate manipulatory and processing behavior (Liem, 1973;Liem and Osse, 1975;Liem and Greenwood, 1981;Lauder, 1983bLauder, , 1985aSanford and Lauder, 1989;Sibbing, 1991;Vandewalle et al., 1994;Galis and Drucker, 1996), a condition known as "pharyngognathy" (Liem and Greenwood, 1981; Fig. 1.3). ...
... Many elements of the pharyngeal skeleton in bony fishes bear teeth (as do palatal and neurocranial bones) which are used to hold, grasp, manipulate, transport, and process food. In some teleosts, upper and lower tooth-bearing elements of the pharyngeal arches interact to form an internal set of "pharyngeal jaws" used in elaborate manipulatory and processing behavior (Liem, 1973;Liem and Osse, 1975;Liem and Greenwood, 1981;Lauder, 1983bLauder, , 1985aSanford and Lauder, 1989;Sibbing, 1991;Vandewalle et al., 1994;Galis and Drucker, 1996), a condition known as "pharyngognathy" (Liem and Greenwood, 1981; Fig. 1.3). ...
... Letters refer to muscle groups that act on the jaws to produce complex crushing, grinding, and transport movements. From Liem and Greenwood (1981), reproduced with permission of the Society for Integrative and Comparative Biology. the prey's inertia. Tetrapods could not employ such inertial suction when they first began to feed in the terrestrial environment, but they nonetheless exploited the hyoid mobility inherited from their piscine ancestors when feeding on land (Shaffer and Lauder, 1988;Lauder, 1994, 1995;Reilly, 1996). ...
... For example, the morphology of the pharyngeal jaw complex suggested a close relationship between pomacentrids (damselfishes) and cichlids within Labroidei (Wainwright et al. 2012;Lauder and Liem 1983), although this close relationship has been overturned in recent molecular phylogenies (e.g., Betancur-R et al. 2017). Cichlids differ significantly from other fishes in the muscle and bone architecture of their pharyngeal apparatus (Liem and Greenwood 1981;Kaufman and Liem 1982;Seehausen et al. 1999;Stiassny and Jensen 1987). ...
... The earliest hypothesis for the sonic mechanism in cichlids focused on the pharyngeal teeth (Lanzing 1974;Lanzing and Higginbotham 1976). The cichlid pharyngeal jaws have been suggested as a critical evolutionary innovation responsible for driving the ecological success and diversification of the family (Liem 1973(Liem , 1978(Liem , 1979Liem and Greenwood 1981;Liem and Osse 1975). Early observations of cichlid noted that sounds associated with feeding behavior showed similar acoustic properties to communicative sounds (Lanzing 1974); however, some species show differences in the acoustic properties between these sound types (Longrie et al. 2009). ...
Bioacoustics has become a key feature of cichlid behavioral studies over the last 20 years, due in large part to new technologies and software. The hypothesis that some cichlid species produce species-specific sounds is gaining support with data from several studies. Sounds are specific to behavioral context for many species. Cichlids are advanced teleost fishes possessing a complex pharyngeal jaw. This morphological feature has been proposed as the key functional innovation responsible for the evolutionary success and explosive adaptive radiation of the group. This evolutionary success has been mostly attributed to their expanded adaptability to process a wide variety of food types due to the capability of thoroughly grinding food in the pharyngeal apparatus, an ability that most other fishes lack. The evidence regarding the role of the pharyngeal jaw complex in sound production is evaluated, and suggests that this same morphology enables cichlids to produce a complex and varied acoustic repertoire. Although, the sonic mechanism may be more complex morphologically than just the pharyngeals clacking. More studies are needed to carefully document the sounds correlated to specific behaviors of cichlids and to statistically examine the species specificity of sympatric species sounds. Future research is needed that experimentally tests the response of female fish to acoustic playback combined with visual and chemical cues in order to determine how critical sound communication is to the sympatric evolution of cichlid species.
... This second set of jaws has the potential to decouple prey capture from prey processing, allowing specialization of the oral and pharyngeal jaws for different functions and promoting trophic diversification. Several lineages of ray-finned fishes have evolved a derived condition of the pharyngeal jaws, termed "pharyngognathy" (but often simply "pharyngeal jaws" in the literature; Stroud and Losos 2016), which renders these jaws functionally more potent and represents a classic innovation hypothesized to have been a stimulus to adaptive radiation (Liem and Greenwood 1981). Pharyngognathy involves fusion of the left and right fifth ceratobranchial bones into a single lower pharyngeal jaw element, a synovial joint between the dorsal surface of the upper jaw bones and the underside of the neurocranium, and a muscular sling that directly connects the lower pharyngeal jaw to the neurocranium (Liem and Greenwood 1981;Stiassny and Jensen 1987; fig. ...
... Several lineages of ray-finned fishes have evolved a derived condition of the pharyngeal jaws, termed "pharyngognathy" (but often simply "pharyngeal jaws" in the literature; Stroud and Losos 2016), which renders these jaws functionally more potent and represents a classic innovation hypothesized to have been a stimulus to adaptive radiation (Liem and Greenwood 1981). Pharyngognathy involves fusion of the left and right fifth ceratobranchial bones into a single lower pharyngeal jaw element, a synovial joint between the dorsal surface of the upper jaw bones and the underside of the neurocranium, and a muscular sling that directly connects the lower pharyngeal jaw to the neurocranium (Liem and Greenwood 1981;Stiassny and Jensen 1987; fig. 1). ...
Functional innovations are often invoked to explain the uneven distribution of ecological diversity. Innovations may provide access to new adaptive zones by expanding available ecological opportunities and may serve as catalysts of adaptive radiation. However, diversity is often unevenly distributed within clades that share a key innovation, highlighting the possibility that the impact of the innovation is mediated by other traits. Pharyngognathy is a widely recognized innovation of the pharyngeal jaws that enhances the ability to process hard and tough prey in several major radiations of fishes, including marine wrasses and freshwater cichlids. We explored diversification of lower pharyngeal jaw shape, a key feature of pharyngognathy, and the extent to which it is influenced by head shape in Neotropical cichlids. While pharyngeal jaw shape was unaffected by either head length or head depth, its disparity declined dramatically with increasing head width. Head width also predicted the rate of pharyngeal jaw evolution such that higher rates were associated with narrow heads. Wide heads are associated with exploiting prey that require intense processing by pharyngeal jaws that have expanded surfaces for the attachment of enlarged muscles. However, we show that a wide head constrains access to adaptive peaks associated with several trophic roles. A constraint on the independent evolution of pharyngeal jaw and head shape may explain the uneven distribution of ecological diversity within a clade that shares a major functional innovation.
... Processing mechanisms differ substantially across vertebrate groups but coordinated rhythmic and cyclic movements of the jaw, skull and hyobranchial (tongue) system are common in cartilaginous and ray-finned fishes, lungfishes and amniotes (Bemis and Lauder, 1986;Dean et al., 2005;Gans et al., 1978;Gans and Vree, 1986;Gintof et al., 2010;Sanford and Lauder, 1989;Schwenk and Rubega, 2005;Schwenk and Wake, 1993;Wainwright et al., 1989). Whereas some cartilaginous fishes, including sharks and rays, use rhythmic chewing to process food within their mandibular jaw systems (Dean et al., 2005;Kolmann et al., 2016), ray-finned fishes exhibit three 'jaw systems' for food processing: (i) raking, using the tongue-bite apparatus (Camp et al., 2009;Hilton, 2001;Konow et al., 2013;Konow and Sanford, 2008;Lauder, 1989, 1990), (ii) grinding, using the pharyngeal jaw apparatus (referred to as 'pharyngognathy') (Gidmark et al., 2014;Liem and Greenwood, 1981;Wainwright, 2002;Wainwright et al., 1989) and (iii) chewing, using the mandibular jaw apparatus (Fernandez and Motta, 1997;Gintof et al., 2010;Konow and Sanford, 2008;Lauder, 1981). While raking and pharyngognathy are derived mechanisms that only occur in some ray-finned fish groups, chewing occurs in both fishes and amniotes (Gans et al., 1978;Gintof et al., 2010;Herring et al., 2001;Hiiemae and Crompton, 1985;Schwenk, 2000a;Schwenk and Rubega, 2005). ...
... In raking, the tongue loops in the reverse, clockwise direction (rostrum facing left) and although the tongue shreds the food against palatal dentition in both systems, the power stroke in raking involves tongue retraction versus tongue protraction in the newt system. However, some groups of spiny-rayed (acanthomorph) fishes, including anabantoids (Konow et al., 2013;Liem and Greenwood, 1981), may have evolved a raking analogue with the same tongue motion pattern as seen in the newt. In amniotes, cyclic movements of the tongue system during a bout of chewing first help position the food between the teeth and later help gradually transport food towards the oesophagus in preparation for swallowing (Bramble and Wake, 1985;Herrel et al., 2008;Hiiemae and Crompton, 1985;Smith, 1984). ...
Food processing refers to any form of mechanical breakdown of food prior to swallowing. Variations of this behaviour are found within all major gnathostome groups. Chewing is by far the most commonly used intraoral processing mechanism and involves rhythmic mandibular jaw and hyobranchial (tongue) movements. Chewing occurs in chondrichthyans (sharks and rays), actinopterygians (rayfinned fishes), dipnoi (lungfishes) as well as amniotes and involves similarities in the patterns of muscle activity and movement of the feeding apparatus. It has been suggested that amniote chewing, which involves the interaction of movements of the mandibular jaw and the muscular tongue, has evolved as part of the tetrapod land invasion. However, little is known about food-processing mechanisms in lissamphibians, which might have retained many ancestral tetrapod features. Here, we identified a processing mechanism in the salamandrid newt, Triturus carnifex, which after prey capture displays cyclic head bobbing in concert with rhythmic jaw and tongue movements. We used high-speed fluoroscopy, anatomical reconstructions and analyses of stomach contents to show that newts, although not using their mandibular jaws, deploy a derived processing mechanism where prey items are rasped rhythmically against the dentition on the mouth roof, driven by a loop motion of the tongue. We then compared patterns and coordination of jaw and tongue movements across gnathostomes to conclude that food processing in this newt species shares traits with processing mechanisms in fish as well as amniotes. This discovery casts salamanders as promising models for reconstructing the evolution of intraoral processing mechanisms at the fish–tetrapod split.
... The Pomacentridae possess at least two morpho-functional novelties. (1) Similar to cichlids, labrids and embiotocids, the pomacentrids have developed modifi ed pharyngeal jaws that permit effi cient food processing (Liem and Greenwood 1981, Stiassny and Jensens 1987, Galis and Snelderwaard 1997, Wainwright et al. 2012) which could be an important functional innovation. ...
... The pharyngeal jaws Damselfi shes have an articulation between the lower pharyngeal jaw and the pectoral girdle (Liem and Greenwood 1981, Stiassny and Jensens 1987, Galis and Snelderwaard 1997Fig. 1). ...
... The Pomacentroid clade of Bleeker (1877) was a member of Müller's (1843) Pharyngonathi acanthopterygii that include taxa with at least (1) united left and right lower jaw elements (fi fth ceratobranchials), (2) a muscular sling that directly connects the underside of the neurocranium with the lower pharyngeal jaw; and (3) a mobile diarthrotic articulation of the upper pharyngeal jaws with the neurocranium (Stiassny 1981, Kaufman and Liem 1982, Wainwright et al. 2012. These morphological and functional characters were proposed as synapomorphies uniting an expanded Labroidei clade (Liem and Greenwood 1981) that included Cichlidae, Embiotocidae, Labridae, Odacidae and Scaridae. One year later, Kaufman and Liem (1982) added Pomacentridae to the Labroidei. ...
... In pomacentrids, the characteristics of the lower pharyngeal jaw (LPJ) are a Y-shape (and width is greater than the length), no trace of a central sutural union, a well-developed median keel on the ventral face of the bone, and tooth rows arranged radially across the LPJ with teeth located over the median region of the jaw (Kaufman andLiem 1982, Stiassny andJensen 1987). Although it is not found in all the pomacentrids (e.g., Microspathodon and Chromis), pharyngocleithral articulations can join the expanded lateral horns of the LPJ to the cleithrum (Liem 1973, Liem and Greenwood 1981, Kaufman and Liem 1982, Stiassny and Jensen 1987. Liem (1973) proposed that pharyngognathy has major implications for feeding performance because the fusion of the LPJ in a single plate allows the combination of the force exerted by right and left muscle and leads to the enhancement of force and the ability to crush hard prey (Wainwright et al. 2012). ...
... However, it cannot be determined if there is a diarthrosis between the upper pharyngeal jaws and the basicranium, and whether the lower pharyngeal jaws are fused. Fishes having those powerful pharyngeal jaws can be referred to as being pharyngognathous (see Liem & Greenwood, 1981). The development of large dentigerous pharyngeal bones has been observed in several percoids (see Rosen & Patterson, 1990), such as the Centrarchidae (see Lauder, 1983), Gerreidae, Girellidae, Haemulidae, Kyphosidae, Leiognathidae, Priscacaridae (Grande, 1984), Eocottidae, Sciaenidae, Scorpididae, Sparidae, and the extinct genus Amphiperca (see Micklich, 1985). ...
... Regan (1913) definitively demonstrated that the 'pharyngognathous' fishes represent an unnatural assemblage of not closely related groups which share ankylosed lower pharyngeal bones. More recently, the increased interest concerning the systematic and phylogenetic relevance of gill arches has lead to reevaluation of the pharyngognathous fishes, in order to re-define their limits and relationships based on cladistic criteria (see, e.g., Nelson, 1967;Stiassny, 1981;Liem & Greenwood, 1981;Stiassny & Jensen, 1987;Rosen & Patterson, 1990). The significance of gill arch anatomy in defining phylogenetic relationships within the Perciformes is unclear. ...
The marine percoid fish Dules temnopterus Agassiz, 1836 from the Eocene of Monte Bolca, northern Italy, is redescribed in
detail and assigned to the new genus Jimtylerius. Due to its unique combination of features (e.g. jaws with multiserial, short, and blunt
teeth; canines absent; hypertrophied pharyngeal bones with large molariform teeth; caudal skeleton with five autogenous hypurals, three epurals
and two uroneurals; first uroneural fused with the ultimate centrum; procurrent spur present; caudal fin with 17 principal rays; 10 dorsal
procurrent rays and 8 ventral procurrent rays; predorsal formula /0+0/0+2/1+1/; dorsal fin continuous, notched, with 10 strong spines and
nine soft rays; posterior dorsal-fin pterygiophores trisegmental; anal fin with three strong spines and seven rays; caudal fin slightly emarginated;
scales relatively large and cycloid), Jimtylerius cannot be assigned to any of the fossil or extant percoid families and it is placed incertae
sedis in the Percoidei. Some problems of classifying fossil percoid fishes also are discussed. Finally, it is shown that the Late Paleocene percoid
family Asianthidae is not valid and that the “asianthid” genera Asianthus and Eosasia are not clearly distinguishable from each other.
... Moreover, recent studies of functional morphology have concluded that the labroid pharyngeal jaw apparatus is neither behaviourally nor functionally more versatile with respect to that of the body and by the degree of consolidation of the caudal skeletal elements, with the urostyle (pu1+u1+u2) fused to the uroneural plus hypurals 3 and 4, and the hypurals 1 and 2 fused into a triangular plate (see Fujita, 1990). Several studies have suggested that the monophyly of the family Labridae is primarily defined by a series of characters of the pharynx and pharyngeal jaw apparatus (e.g., Regan, 1913; Nelson, 1967; Yamaoka, 1978; Liem & Greenwood, 1981; Kaufman & Liem, 1982; Stiassny & Jensen, 1987). Unfortunately, these pharyngeal characters refer to skeletal or muscular structures not preserved or inaccessible in the available specimens of Frippia n. gen., such as the epibranchials, pharyngobranchials, pharyngocleithral articulation and pharyngocleithralis and levator posterior muscles (see Kaufman & Liem, 1982). ...
... The evaluation of the potential labroid affinities of Frippia n. gen. is more complex. The limits and composition of this extremely diverse and successful extant group have been relatively unstable, characterized by repeated additions in the last four decades (see Greenwood et al., 1966; Liem & Greenwood, 1981; Kaufman & Liem, 1982). Kaufman & Liem (1982) The premaxilla of Frippia n. gen. ...
A new genus and species of percoid fish, Frippia labroiformis n. gen. n. sp. from the Eocene of Pesciara di Bolca, northern Italy, is described based on three well-preserved specimens characterized by a moderately elongate body and a short and deep caudal peduncle. Frippia n. gen. exhibits a unique combination of features, including the following: weak pharyngeal apophysis of the parasphenoid; orbit with sclerotic ossifications; jaws with single series of strong conical teeth; slightly curved preopercle with smooth posterior margin; opercle devoid of spines; six branchiostegal rays; blunt and conical lower pharyngeal teeth; 26 (10+16) vertebrae; caudal skeleton with urostylar complex fused to uroneural and third and fourth hypurals, first and second hypurals fused, fifth hypural and parhypural autogenous, three epurals, autogenous haemal spines of second and third preural vertebrae, and low neural crest on second preural vertebra; caudalfin rounded with 17 principal rays and six to seven upper and five to six lower procurrent rays; predorsal formula 0/0/0+2/1+1/; continuous dorsal fin with nine spines and 14 soft rays; anal fin with three strong spines and 10 rays; pectoral fin with 15 rays; pelvic fin with one spine and five long rays, the longest reaching posteriorly to anal-fin origin; scales relatively large, thin and finely ctenoid on trunk and cycloid on head Because of its unique combination of features Frippia n. gen. cannot be confidently assigned to any of the existing extant or fossil percoid families and it is therefore interpreted herein as incertae sedis within the Percoidei.
... Whereas some studies have used contrast staining to image one or two fish species (Brocklehurst et al., 2019), and typically model organisms (Descamps et al., 2014), few evolutionary studies have offered a workflow for those of us exploring non-model animals (but see Camilieri-Asch et al., 2020;Kolmann et al., 2018;Rutledge et al., 2019). Moreover, fishes have some of the greatest diversity of organ and sensory modalities among vertebrates, from electric organs (EOs) that some fishes use for both communication and navigation, to the photophores of midwater (mesopelagic) fishes (the most abundant vertebrates by biomass on the planet), to the muscular slings of secondary jaws located in the pharynx of fishes like morays and cichlids (Crampton, 2019;Liem & Greenwood, 1981;Martin et al., 2022). For example, studies have made good use of staining agents like PTA for visualizing the complex sucker disk of remoras (Echeneidae), as well as sifting and filtering epibranchial organs in carp and gobies (Brodnicke et al., 2022;Cohen & Hernandez, 2018). ...
Computed tomography (CT) scanning and other high‐throughput three‐dimensional (3D) visualization tools are transforming the ways we study morphology, ecology and evolutionary biology research beyond generating vast digital repositories of anatomical data. Contrast‐enhanced chemical staining methods, which render soft tissues radio‐opaque when coupled with CT scanning, encompass several approaches that are growing in popularity and versatility. Of these, the various diceCT techniques that use an iodine‐based solution like Lugol's have provided access to an array of morphological data sets spanning extant vertebrate lineages. This contribution outlines straightforward means for applying diceCT techniques to preserved museum specimens of cartilaginous and bony fishes, collectively representing half of vertebrate species diversity. This study contrasts the benefits of using either aqueous or ethylic Lugol's solutions and reports few differences between these methods with respect to the time required to achieve optimal tissue contrast. It also explores differences in minimum stain duration required for different body sizes and shapes and provides recommendations for staining specimens individually or in small batches. As reported by earlier studies, the authors note a decrease in pH during staining with either aqueous or ethylic Lugol's. Nonetheless, they could not replicate the drastic declines in pH reported elsewhere. They provide recommendations for researchers and collections staff on how to incorporate diceCT into existing curatorial practices, while offsetting risk to specimens. Finally, they outline how diceCT with Lugol's can aid ichthyologists of all kinds in visualizing anatomical structures of interest: from brains and gizzards to gas bladders and pharyngeal jaw muscles.
... The taxonomy of labrids has changed significantly in light of molecular phylogenetics. The presence of a pharyngeal jaw apparatus (pharyngognathy) has historically united labrids in the perciform suborder Labroidei, with cichlids, damselfishes, and surfperches (Liem and Greenwood 1981). However, molecular studies have found that pharyngognathy has evolved multiple times, with cichlids, damselfishes, and surfperches allied with the percomorph group Ovalentaria Wainwright et al. 2012;Betancur-R. ...
Phylogenomic analysis of large genome-wide sequence data sets can resolve phylogenetic tree topologies for large species groups, help test the accuracy of and improve resolution for earlier multilocus studies and reveal the level of agreement or concordance within partitions of the genome for various tree topologies. Here we used a target-capture approach to sequence 1,088 single-copy exons for more than 200 labrid fishes together with more than 100 outgroup taxa to generate a new data-rich phylogeny for the family Labridae. Our time-calibrated phylogenetic analysis of exon-capture data pushes the root node age of the family Labridae back into the Cretaceous to about 79 Ma years ago. The monotypic Centrogenys vaigiensis, and the order Uranoscopiformes (stargazers) are identified as the sister lineages of Labridae. The phylogenetic relationships among major labrid subfamilies and within these clades were largely congruent with prior analyses of select mitochondrial and nuclear datasets. However, the position of the tribe Cirrhilabrini (fairy and flame wrasses) showed discordance, resolving either as the sister to a crown julidine clade or alternatively sister to a group formed by the labrines, cheilines and scarines. Exploration of this pattern using multiple approaches leads to slightly higher support for this latter hypothesis, highlighting the importance of genome-level data sets for resolving short internodes at key phylogenetic positions in large, economically important groups of coral reef fishes. More broadly, we demonstrate how accounting for sources of biological variability from incomplete lineage sorting and exploring systematic error at conflicting nodes can aid in evaluating alternative phylogenetic hypotheses.
... The more complex cranial morphology is also argued to be the basis for the evolution of the wide range of feeding mechanisms in actinopterygians (Hulsey et al., 2005;Wainwright et al., 2004). In fact, in addition to chewing to process their food, derived taxa of ray-finned fishes have evolved two additional food processing mechanisms: (i) raking, using the tongue-bite apparatus to shred and disable prey (Camp et al., 2009;Hilton, 2001;Konow and Sanford, 2008;Konow et al., 2013;Sanford and Lauder, 1989;Sanford and Lauder, 1990) and (ii) pharyngognathy, using the pharyngeal jaw apparatus to grind food (Gidmark et al., 2014;Liem and Greenwood, 1981;Wainwright, 2002;Wainwright et al., 1989). Dipnoi (Fig. 2) also referred to as lungfish, as lobe-finned fishes (sarcopterygians), exhibit fleshy, lobed, and paired fins, which are connected to the body by a single bone giving them their name. ...
In order to survive, animals have to eat - at least during certain phases of life, since the energy required for almost all life processes comes from the assimilation of existing organic compounds. Intraoral food processing as one of the four stages of feeding refers to any mechanical reduction or food preparation in the oral cavity before swallowing. Intraoral food processing involves rhythmic, cyclical, and usually coordinated movements of the skull, mandible, and tongue (i.e., the feeding apparatus). Jawed fishes (chondrichthyans, actinopterygians, and dipnoi) mostly use their mandible to process food, and hence this mechanism qualifies as chewing. The general pattern of these movements is mainly conserved across fishes. However, along with the transition from water to land during early tetrapod evolution, aquatic fish-like food processing (i.e., chewing and hydrodynamic food transport) has been replaced by terrestrial amniote-like food processing (i.e., chewing and tongue-based food transport). Although intraoral food processing occurs amongst almost all major groups of jawed vertebrates, it had been argued that recent amphibians mostly lack intraoral food processing mechanisms. The thesis at hand aims to expand our knowledge of the ontogeny and evolution of intraoral food processing in salamanders. I demonstrate that salamanders commonly use intraoral food processing and that the mechanism of food processing seems to switch from mandible-based chewing in larval morphotypes to a tongue-based palate rasping in metamorphic morphotypes. The ontogenetic switch in intraoral food processing that occurs in metamorphosing salamanders might be argued to resemble an analogue to the phylogenetic shift that happened during the evolution of early tetrapods. This analogue might suggest that direct tongue-based interactions with food have evolved under aquatic conditions hence, suggesting that terrestrial style feeding might have preceded the water-land transition.
... Pomacentridae have a long history of being associated with other pharyngognathous families like Cichlidae, Embiotocidae, and/or Labridae (e.g., Müller, 1843Müller, , 1845Günther, 1862;Jordan and Evermann, 1898: 1543-1544Jordan and Snyder, 1902;Nelson, 1967;Masuda et al., 1975). Liem and Greenwood (1981) identified name did not gain much traction, with only passing mention by a few authors (e.g., Betancur-R. et al., 2013aBetancur-R. ...
... Intraoral food processing is used by many jawed vertebrates to facilitate swallowing and digestion Schwenk, 2000;Schwenk and Rubega, 2005) or to immobilize prey (Dalrymple et al., 1985;Konow et al., 2013) and thus likely avoid being hurt by struggling prey. Such intraoral mechanical reduction of food is very diverse amongst gnathostomes and can involve a variety of processing systems, including oral jaws (Bemis and Lauder, 1986;Bhullar et al., 2019;Crompton and Hiiemae, 1970;Gans et al., 1978;Gintof et al., 2010;Ross et al., 2007;Smith, 1982), pharyngeal jaws (Gidmark et al., 2013(Gidmark et al., , 2014Liem and Greenwood, 1981;Wainwright et al., 2012), the tongue-bite apparatus (Camp et al., 2009;Konow et al., 2013;Sanford and Lauder, 1989) and rough palatal structures in combination with a movable tongue (Griffiths, 1978;Heiss et al., 2019;Matsumoto and Evans, 2017;Werth, 2000). ...
Intraoral food processing mechanisms are known for all major vertebrate clades, but form and function of systems used to crush, grind, or puncture food items can differ substantially between and within clades. Most vertebrates, display flexible mechanisms of intraoral food processing with respect to different environmental conditions or food types. It has recently been shown that newts use cyclical loop-motions of the tongue to rasp prey against the palatal dentition. However, it remains unknown if newts can adjust their food processing behavior in response to different food types or environmental conditions. Newts are interesting models for studying the functional adaptation to different conditions, because of their unique and flexible lifestyle: they seasonally change between aquatic and terrestrial habitats, adapt their prey-capture mode to the respective environment and consume diverse food types with different mechanical properties. Using x-ray high-speed recordings, anatomical investigations, behavioral analyses and mechanical property measurements, we test the effects of the medium where feeding occurs (water/air) and the food type (maggot, earthworm, cricket) on the processing behavior in Triturus carnifex We discover that food processing, by contrast to prey capture, differs only slightly between aquatic and terrestrial habitats. However, newts adjust the number of processing cycles to different prey types: while maggots are processed extensively, earthworm pieces are barely processed at all. We conclude that, in addition to food mechanical properties, sensory feedback such as smell and taste appear to induce flexible processing responses, while the medium where feeding occurs appears to have less of an effect.
... This second set of jaws in the pharynx of cichlids is primarily used for food processing, allowing a functional decoupling between food uptake and mastication (Liem, 1973). While modified pharyngeal jaw structures are found in other groups of fish as well, the ones of the cichlids are characterized by a sutured lower pharyngeal jaw bone (LPJ) (note that this trait of a unified LPJ is shared with closely related percoid families such as labrids or embiotocids (Liem & Greenwood, 1981;Galis & Drucker, 1996;Hulsey et al., 2006)). Cichlids show a great diversity in the morphology of the pharyngeal jaw apparatus, and it has been demonstrated that LPJ shape and dentition are correlated to the feeding ecology of a species (Liem, 1973;Meyer, 1989;Muschick et al., 2012). ...
Food resource specialization within novel environments is considered a common axis of diversification in adaptive radiations. Feeding specializations are often coupled with striking morphological adaptations and exemplify the relation between morphology and diet (phenotype–environment correlations), as seen in, for example, Darwin finches, Hawaiian spiders, and the cichlid fish radiations in East African lakes. The cichlids' potential to rapidly exploit and occupy a variety of different habitats has previously been attributed to the variability and adaptability of their trophic structures including the pharyngeal jaw apparatus. Here we report a reciprocal transplant experiment designed to explore the adaptability of the trophic structures in highly specialized cichlid fish species. More specifically, we forced two common but ecologically distinct cichlid species from Lake Tanganyika, Tropheus moorii (rock‐dweller), and Xenotilapia boulengeri (sand‐dweller), to live on their preferred as well as on an unpreferred habitat (sand and rock, respectively). We measured their overall performance on the different habitat types and explored whether adaptive phenotypic plasticity is involved in adaptation. We found that, while habitat had no effect on the performance of X. boulengeri , T. moorii performed significantly better in its preferred habitat. Despite an experimental duration of several months, we did not find a shift in the morphology of the lower pharyngeal jaw bone that would be indicative of adaptive phenotypic plasticity in this trait.
... Kaufman & Liem, 1982; Liem, 1973; Liem & Greenwood, 1981; Stiassny & Jensen, 1987)[28,39,38,58] . ...
Pharyngeal jaw apparatus is complex musculo-skeletal system which are modification of gill arch elements that is useful for masticating and transporting of food material. It consist of two independent upper plate and single fused lower plate that are containing various types of unicuspid, bicuspid or molariform dentition. Relationship between pharyngeal jaw for feeding and sound production may have profound evolutionary implications. It has serving as a possible mechanism for sound production; trophic biology and reproductive biology could be directly linked by this structure. Consequently, the dual use of the pharyngeal jaw may serve as a mechanism mediating the sympatric speciation of cichlid fishes. Intraspecific pharyngeal variations also occurred in some fishes that helpful to understanding lineage relationships.
... A ausência de fósseis anteriores ao Eoceno, assim como o fato de todos os Labroidei próximos aos Cichlidae serem marinhos (cf., Liem & Greenwood, 1981), corroboram a interpretação da distribuição desta família como o resultado de colonizações independentes do ambiente continental na América do Sul, oriunda da África, a partir de uma linhagem originalmente tolerante a águas oceânicas, provavelmente durante o início do Terciário (Murray, 2001). ...
The history of the ichthyofaunal biodiversity in South America started after the complete separation between these continents, by the end of the Lower Cretaceous, at least 90 million years ago. The extant ichthyofauna in both South America and Africa can be divided in two main categories of taxa: 1) the freshwater taxa, which survived the separation of South America and Africa on at least one of the continents, such as lepidosirenids, osteoglossids, characids, siluriforms, and some cyprinodontiforms; and 2) the taxa which had a marine ancestor and colonized each continent after the fragmentation of the western Gondwana, like synbranchids, cichlids, and polycentrids. In this paper, we deal with another major problem concerning the fossil ichthyofaunas: understand if the species are primarily from freshwater or if they are momentarily in freshwater.
... Note that one group of ray-finned fishes, moray eels, has evolved the exceptional capacity to directly transport food from the jaws to the esophagus by extreme protrusion of the pharyngeal jaws (Mehta and Wainwright, 2007a,b). However, forward displacements of the pharyngeal jaws in fishes are generally confined to the posterior region of the pharynx (Liem and Greenwood, 1981;Sponder and Lauder, 1981;Wainwright, 1989). Yet, pharyngeal jaw transport has been shown to be involved in the mudskipper Periophthalmus when feeding on land (Sponder and Lauder, 1981). ...
Transitions to terrestrial environments confront ancestrally aquatic animals with several mechanical and physiological problems owing to the different physical properties of water and air. As aquatic feeders generally make use of flows of water relative to the head to capture, transport and swallow food, it follows that morphological and behavioral changes were inevitably needed for the aquatic animals to successfully perform these functions on land. Here, we summarize the mechanical requirements of successful aquatic-to-terrestrial transitions in food capture, transport and swallowing by vertebrates and review how different taxa managed to fulfill these requirements. Amphibious ray-finned fishes show a variety of strategies to stably lift the anterior trunk, as well as to grab ground-based food with their jaws. However, they still need to return to the water for the intra-oral transport and swallowing process. Using the same mechanical perspective, the potential capabilities of some of the earliest tetrapods to perform terrestrial feeding are evaluated. Within tetrapods, the appearance of a mobile neck and a muscular and movable tongue can safely be regarded as key factors in the colonization of land away from amphibious habitats. Comparative studies on taxa including salamanders, which change from aquatic feeders as larvae to terrestrial feeders as adults, illustrate remodeling patterns in the hyobranchial system that can be linked to its drastic change in function during feeding. Yet, the precise evolutionary history in form and function of the hyolingual system leading to the origin(s) of a muscular and adhesive tongue remains unknown.
... Both sets form via shared developmental mechanisms and are considered developmentally homologous 28 . Interesting modularity occurs whereby some species, such as zebrafish, lack oral and dorsal pharyngeal teeth 29 while other species have multiple toothed ceratobranchials, pharyngobranchials, and sometimes toothed basihyal and hypobranchials 30 . In sticklebacks, pharyngeal teeth are found ventrally on the fifth ceratobranchial and dorsally on the anterior and posterior pharyngobranchials 31 . ...
The posterior pharyngeal segments of the vertebrate head give rise to the branchial skeleton, the primary site of food processing in fish. The morphology of the fish branchial skeleton is matched to a species' diet. Threespine stickleback fish (Gasterosteus aculeatus) have emerged as a model system to study the genetic and developmental basis of evolved differences in a variety of traits. Marine populations of sticklebacks have repeatedly colonized countless new freshwater lakes and creeks. Adaptation to the new diet in these freshwater environments likely underlies a series of craniofacial changes that have evolved repeatedly in independently derived freshwater populations. These include three major patterning changes to the branchial skeleton: reductions in the number and length of gill raker bones, increases in pharyngeal tooth number, and increased branchial bone lengths. Here we describe a detailed protocol to dissect and flat-mount the internal branchial skeleton in threespine stickleback fish. Dissection of the entire three-dimensional branchial skeleton and mounting it flat into a largely two-dimensional prep allows for the easy visualization and quantification of branchial skeleton morphology. This dissection method is inexpensive, fast, relatively easy, and applicable to a wide variety of fish species. In sticklebacks, this efficient method allows the quantification of skeletal morphology in genetic crosses to map genomic regions controlling craniofacial patterning.
... variable across teleosts. While some fish have teeth covering most bones of their branchial skeletons (Liem and Greenwood, 1981), others, such as zebrafish, have lost all oral and dorsal pharyngeal teeth and rely solely on the ventral pharyngeal tooth plate attached to the fifth ceratobranchial (Stock, 2007). As previously described (Swinnerton, 1902;Anker, 1974) sticklebacks have teeth on the premaxilla and dentary in the oral jaw, and on the fifth ceratobranchial and the second and fused third/fourth pharyngobranchials in the branchial skeleton. ...
Teeth have long served as a model system to study basic questions about vertebrate organogenesis, morphogenesis, and evolution. In nonmammalian vertebrates, teeth typically regenerate throughout adult life. Fish have evolved a tremendous diversity in dental patterning in both their oral and pharyngeal dentitions, offering numerous opportunities to study how morphology develops, regenerates, and evolves in different lineages. Threespine stickleback fish (Gasterosteus aculeatus) have emerged as a new system to study how morphology evolves, and provide a particularly powerful system to study the development and evolution of dental morphology. Here, we describe the oral and pharyngeal dentitions of stickleback fish, providing additional morphological, histological, and molecular evidence for homology of oral and pharyngeal teeth. Focusing on the ventral pharyngeal dentition in a dense developmental time course of lab-reared fish, we describe the temporal and spatial consensus sequence of early tooth formation. Early in development, this sequence is highly stereotypical and consists of seventeen primary teeth forming the early tooth field, followed by the first tooth replacement event. Comparing this detailed morphological and ontogenetic sequence to that described in other fish reveals that major changes to how dental morphology arises and regenerates have evolved across different fish lineages. J. Morphol., 2016. © 2016 Wiley Periodicals, Inc.
... The monogeneric Pristolepididae form a monophyletic group with the percomorph taxa Nandidae, Badidae, Anabantidae, Helostomatidae, Osphronemidae and Channidae, characterized uniquely among percomorphs by the possession of teeth on the parasphenoid (Britz 1995(Britz , 2003Wiley & Johnson 2010). In Pristolepis, the well developed parasphenoid toothpatch is opposed by a greatly enlarged and toothed basibranchial toothplate together forming an effective crushing apparatus in the pharynx in addition to the pharyngeal jaws (Liem & Greenwood 1981). ...
Pristolepis rubripinnis, new species, from the Pamba and Chalakudy rivers in Kerala, India, is distinguished from all other species of the genus by its colour pattern, which includes orange-red soft dorsal, soft anal and caudal fins, and a yellow to orange pelvic fin. It differs further from its southern Indian congener P. marginata in having 4 or 5 scales above the lateral line (vs. 3) and 10 scales below it (vs. 9).
... Both anterior and posterior lateral wings have also been found in some fossil teleosts (Lebedkina 2004). However, in some ancestral teleost groups (many Cretaceous and Eocene taxa and some extant osteoglossomorphs, clupeomorphs and elopomorphs), a denticulated parasphenoid is present (Gregory 1933;Gosline 1965;Liem and Greenwood 1981;Patterson 1998). ...
The parasphenoid is located in the cranium of many vertebrates. When present, it is always an unpaired, dermal bone. While most basal vertebrates have a parasphenoid, most placental mammals lack this element and have an unpaired, dermal vomer in a similar position (i.e. associated with the same bones) and with a similar function. As such, the parasphenoid and the vomer were considered homologous by some early twentieth century researchers. However, others questioned this homology based on comparisons between mammals and reptiles. Here we investigate the parasphenoid bone across the major vertebrate lineages (amphibians, reptiles, mammals and teleosts) including both developmental and evolutionary aspects, which until now have not been considered together. We find that within all the major vertebrate lineages there are organisms that possess a parasphenoid and a vomer, while the parasphenoid is absent within caecilians and most placental mammals. Based on our assessment and Patterson's conjunction tests, we conclude that the non-mammalian parasphenoid and the vomer in mammals cannot be considered homologous. Additionally, the parasphenoid is likely homologous between sarcopterygian and actinopterygian lineages. This research attempts to resolve the issue of the parasphenoid homology and highlights where gaps in our knowledge are still present.
... Kaufman & Liem (1982) proposed a new arrangement of the suborder Labroidei, considering Scaridae and Odacidae as part of Labridae. However, Labridae is apparently a natural group (Liem & Greenwood, 1981), with many gaps in its relationship with other fish groups, without a clear justification for a subfamily rank of the Scaridae (Bruce & Randall, 1985). The phylogenetic study of Bellwood (1994) is concordant with this opinion. ...
Description of a specimen of Nicholsina denticulata (Evermann & Radcliffe, 1917) (Scaridae, Labroidei) captured in the north of Chile. The information is compared with data presented by previous authors. The distribution of the species in the southeastern Pacific is discussed.
... comprised the families Labridae, Scaridae and Odacidae. Liem and Greenwood (1981) proposed that those three families plus the Embiotocidae and Cichlidae (treated as percoids in G. et al.) constitute a monophyletic group because they share unique morphological and functional specializations associated with pharyngognathy. Kaufman and Liem (1982) diagnosed this expanded Labroidei by three morphological specializations of the pharyngeal jaws and added to it the family Pomacentridae. ...
This chapter summarizes 200 years of the study of cichlid fishes, ranging from the first descriptions of South American and African species in early natural histories to the work of twentieth-century biologists. The rise and influence of evolutionary theory and the development of new knowledge and techniques in the study of genetics are considered central influences in a variety of fields of research involving cichlids, including ecology, ethology, aquaculture, and fisheries. Significant developments and their historical context are considered in relation to the current state of a variety of cichlid research programs, showcasing the extent to which cichlids have become both model species in evolutionary biology and a crucial species in global food production.
Spiny-rayed fishes (Acanthomorpha) dominate modern marine habitats and comprise more than a quarter of all living vertebrate species1-3. It is believed that this dominance resulted from explosive lineage and phenotypic diversification coincident with the Cretaceous-Paleogene (K-Pg) mass-extinction event4. It remains unclear, however, if living acanthomorph diversity is the result of a punctuated burst or gradual accumulation of diversity following the K-Pg. We assess these hypotheses with a time-calibrated phylogeny inferred using ultraconserved elements from a sampling of species that represent over 91% of all acanthomorph families, as well as an extensive body shape dataset of extant species. Our results indicate that several million years after the end-Cretaceous, acanthomorphs underwent a prolonged and significant expansion of morphological disparity primarily driven by changes in body elongation, and that acanthomorph lineages containing the bulk of the living species diversity originated throughout the Cenozoic. These acanthomorph lineages radiated into distinct regions of morphospace and retained their iconic phenotypes, including a large group of laterally compressed reef fishes, fast-swimming open-ocean predators, bottom-dwelling flatfishes, seahorses, and pufferfishes. The evolutionary success of spiny-rayed fishes is the culmination of a post K-Pg adaptive radiation in which rates of lineage diversification were decoupled from periods of high phenotypic disparity.
Functional decoupling of oral and pharyngeal jaws is widely considered to have expanded the ecological repertoire of cichlid fishes. But, the degree to which the evolution of these jaw systems is decoupled and whether decoupling has impacted trophic diversification remains unknown. Focusing on the large Neotropical radiation of cichlids, we ask whether oral and pharyngeal jaw evolution is correlated and how their evolutionary rates respond to feeding ecology. In support of decoupling, we find relaxed evolutionary integration between the two jaw systems, resulting in novel trait combinations that potentially facilitate feeding mode diversification. These outcomes are made possible by escaping the mechanical trade‐off between force transmission and mobility, which characterizes a single jaw system that functions in isolation. In spite of the structural independence of the two jaw systems, results using a Bayesian, state‐dependent, relaxed‐clock model of multivariate Brownian motion indicate strongly aligned evolutionary responses to feeding ecology. So, while decoupling of prey capture and processing functions released constraints on jaw evolution and promoted trophic diversity in cichlids, the natural diversity of consumed prey has also induced a moderate degree of evolutionary integration between the jaw systems, reminiscent of the original mechanical trade‐off between force and mobility.
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Description of a specimen of Nicholsina denticulata (Evermann & Radcliffe, 1917) (Scaridae, Labroidei) captured in the north of Chile. The information is compared with data presented by previous authors. The distribution of the species in the southeastern Pacific is discussed.
The Osteichthyes—fishes with bony skeletons—comprises the Sarcopterygii (coelacanth and lungfishes) and the Actinopterygii, the latter of which includes the largest class of vertebrates, the Teleostei. The evolutionary radiation of the Teleostei has been spectacular and the dentition has played a major part in trophic adaptation. The main changes in the feeding system have been: increased freedom of movement of the upper jaw, leading to protrusibility of the jaws and increased efficiency of suction during feeding; reduction in the number of teeth; and increased specialization of the pharyngeal dentition for food reduction and of the oral dentition for food acquisition. There has been great diversification of tooth shape and mode of attachment in adaptation to a great range of diets. The lungfishes are a small group in which sectorial tooth plates are formed by fusion of teeth, and the coelacanths are a relict population of benthic carnivorous fishes with piercing teeth.
The relationship between the neotropical genus Cicld. and other members of the family Cichlidae is investigated. Anatomical data from a wide range of functional components are utilized to elucidate the phyletic relationships of the genus. Little evidence is found to support an hypothesis of a close phyletic link between Cichl. and any of the African Cichlidae investigated. Instead, it is suggested that the immediate relationships of Cichl. lie with another neotropical genus, Crenicichla.
Five species of relatively large surfperches (Embiotocidae) exploit the small prey in benthic ‘turf’ on a kelp-forested reef off southern California. Turf contained inorganic debris and ‘items of doubtful food value’ (plants, colonial animals, etc.) which fish mostly rejected, and ‘items of food value’ (amphipods, etc.) which they selected. In mode of food handling, two species selected their food by taking careful bites and swallowing all items, either by picking out small amphipods etc. from algae or plucking larger prey and crushing it between strong pharyngeal teeth. The three others selected food by winnowing bites of turf in their mouth and spitting out the cast. For each species, distribution of foraging effort among microhabitats differed significantly from random, for one species more noticeably so than for the others. All species generally preferred microhabitats with highest densities of valued food items. All but one foraged during the day only. Functional morphological specializations may constrain their foraging modes and diets. The presumed most generalized mode is ‘browser-picker’; ‘crunching’ and ‘oral-winnowing’ are more specialized. The surfperches’ elaborate pharyngognathy is a likely basis of these specializations for greater foraging efficiency.
Because of the high density and viscosity of water, interactions between food particles and fish, on the one hand, and water, on the other, complicate aquatic feeding considerably. Fish have to create a water flow through their buccopharyngeal cavity in order to take up their food. This can be achieved by simply swimming with both the mouth and the opercula widely opened (filter feeding), or by means of active suction (Lauder 1985). In the latter case the volume of the buccopharyngeal and opercular cavities is rapidly expanded so that water and food are drawn in (Muller and Osse 1984; Lauder 1985). Even when the food item or prey is first seized between the oral jaws (e.g. by biting pieces from a large prey), further intrabuccal transport and manipulation in most cases require subsequent suction activity (i.e. hydrodynamic tongue; cf. Liem 1990).
Since the 1980s, a renewed understanding of molecular development has afforded an unprecedented level of knowledge of the mechanisms by which phenotype in animals and plants has evolved. In this volume, top scientists in these fields provide perspectives on how molecular data in biology help to elucidate key questions in estimating paleontological divergence and in understanding the mechanisms behind phenotypic evolution. Paleobiological questions such as genome size, digit homologies, genetic control cascades behind phenotype, estimates of vertebrate divergence dates, and rates of morphological evolution are addressed, with a special emphasis on how molecular biology can inform paleontology, directly and indirectly, to better understand life's past. Highlighting a significant shift towards interdisciplinary collaboration, this is a valuable resource for students and researchers interested in the integration of organismal and molecular biology.
The pirarucu, Arapaima gigas (Osteoglossidae) has a basibranchial toothplate that supports a great density of teeth and helps the food transfer from the oral cavity towards the oesophagus. The lingual teeth appear early during ontogeny of the hyoid and branchial skeleton. On the basibranchial toothplate the teeth are closely set but without any connection, contrary to the "coalesced teeth". The lingual teeth are 4 mm long and 1.0 to 1.5 mm wide; they are constituted of a cone of orthodentine with a distal cap of enameloid. Dentine is divided into two layers: an inner layer of circumpulpal dentine and an external one of palliai dentine. A peculiar specificity of the lingual teeth is the presence of plicidentine in their basal part. So in Actinopterygii, plicidentine is not limited to lepisosteids only. Owing to (i) the different aspect of plicidentine in the two taxa and (ii) their relative phylogenetic distance, we can interprete plicidentine in Actinopterygii as a morphofunctional adaptation to a predation diet.
Research in all fields of biology increasingly uses phylogenetic systematics to interpret biological data in an evolutionary context. It is becoming widely accepted that comparative studies of the correlation of biological features, such as ecomorphological studies, must frame their analyses within the context of a phylogenetic hierarchy rather than treating each taxonomic unit as an independent replicate. Recent methods for the interpretation of ecological and functional data in the framework of a phylogeny can reveal the degree to which ecomorphological characters are correlated with one another, and are congruent with hierarchical cladistic groups. An example of the ecomorphology of labrid fishes is used here to illustrate the application of several of these methods. The structural design and mechanics of the jaws of labrids are tested for ecomorphological associations with the natural diets of these fishes. Methods for analysis of the correlated evolution of both discrete and continuous quantitative characters within a phylogeny are practiced on a single ecomorphological data set. Techniques used include character coding, character mapping, phylogenetic autocorrelation, independent contrasts, and squared change parsimony. These approaches to diverse biological data allow the study of ecomorphology to account for patterns of phylogenetic ancestry. Biomechanics or functional morphology also plays a vital role in the determination of ecomorphological relationships by clarifying the mechanisms by which morphologies can perform behaviors important to the organism’s ecology. The synthesis of systematics with biomechanics is an example of interdisciplinary study in which information exchange can elucidate patterns of evolution in ecomorphology.
Attempts at understanding evolutionary relationships among Paleozoic Dipnoi (lungfish) using cladistic methodology have proved totally unsatisfactory (Miles 1977; Marshall 1987). We attempt to reconstruct the relationships between the better known genera using a method that involves the recognition of lineages based on evolving functional complexes, particularly those involved with food reduction and respiration. Within these broadly defined lineages, we have defined sub-lineages based on evolutionary patterns shown by structures that have been stratigraphically dated; such patterns are found inter alia in the roofing bones and the external dermal bones of the mandible. A number of new suborders and families are recognised; genera for which further morphological data are required before they can be assigned to a higher taxon are indicated; two generic synonyms are recognised.
In appendices, short descriptions are given of two new genera— Pillararhynchus from the Gogo Formation (Upper Devonian) of Western Australia, and Sorbitorhynchus from the Emsian of Guangxi, China.
This chapter focuses on the origin of the amniotic feeding mechanisms as a key event in the evolution of the vertebrate skull. However, it rather describes feeding systems within various amniotes clades, which have been viewed elsewhere. The analysis is centered on the single general theme and contents. In order to understand amniotic feeding mechanisms and their diversifications, it is essential first to understand the structure and the function of the feeding mechanisms in out-group clades. Thus, it examines the feeding mechanisms of fishes and amphibians as a method of determining the functional traits that are likely to have been primitively present in amniotes, and suggests that further experimental studies of extant amniotes and anmniotes taxa can provide a better understanding of evolution of amniotes and more generally vertebrate feeding mechanisms. Various examples for better understanding of general principles of divergence between aquatic and terrestrial feeding systems are discussed. It further explains many functional attributes of the feeding mechanisms of amniotes.
A cladistic analysis of the three recognized patterns of central nervous visual organization
among teleosts reveals that there is a pattern of intermediate complexity representing the
plesiomorphic condition for teleosts, and that there is a simple visual pattern in two unrelated
teleost groups which can be concluded to be a secondarily reduced derived condition, as well as
an elaborate pattern which is present only in acanthomorph teleosts, thus likely representing a
synapomorphy for this taxon. The elaborate central nervous visual pattern, therefore, is one of
many functional-anatomical advanced features characterizing the acanthomorphs. Furthermore,
when neontological and paleontological data is compared with the paleoecological record of early
acanthomorph history during the Late Cretaceous, it is consistent with a hypothesis that this acanthomorph
synapomorphic functional-anatomical complex arose likely in ctenothrissiforms as an
adaptation to the life in the reorganizing reefs of that geologic period.
Microbial fermentation and nutrient synthesis are typically important in organisms with a diet high in fiber (Stevens 1988) — i.e., a diet mainly composed of carbohydrates resistant to endogenous digestive enzymes (Annison 1993). Fermentative digestion thus occurs typically in animals with a diet composed predominantly of plant material (Bergman 1990), and symbioses with microorganisms have been well studied in herbivorous mammals, birds, and reptiles (Stevens 1988). It is therefore surprising that the endosymbiotic communities of the dominant aquatic vertebrate herbivores, the fishes, remain poorly understood. Only recently have diverse microbial communities been reported from the guts of herbivorous fishes (Fishelson et al. 1985, Rimmer and Wiebe 1987, Clements et al. 1989, Clements 1991a), and almost nothing is known of the role of these symbioses in digestion. As a result of this, the material covered in this review will be somewhat different from that covered in other chapters.
A histomorphological study of the development of the pharyngeal jaws in the Carangid fish Trachinotus teraia shows that they transform progressively from tiny organs with sharp superficial teeth, to thick ones with rounded teeth embedded in bony tissue. The morphological transformations take place simultaneously with a shift to a diet based on molluscs.
Though odontogenesis takes place deep in the pharyngeal jaws, at all developmental stages, pharyngeal epithelium participates to the formation of teeth. Long epithelial strands penetrate in the depth of the bony jaw and here induce differentiation of “bell organs.” As the young teeth migrate passively toward the occlusal surface, while the jaw grows, the pharyngeal jaws of Trachinotus teraia almost behave like the “coalesced” teeth of the Tetraodontidae with respect to the morphogenetic processes of their growth. The developmental phenotypic plasticity of the pharyngeal jaws of Trachinotus teraia then may be compared to that of various mollusicivore cichlids.
A labrid fish, Bellwoodilabrus landinii n. gen., n. sp., is described based on a single specimen collected from the Eocene locality of Monte Bolca, northern Italy. Bellwoodilabrus landinii n. gen., n. sp. is characterized by a prominent frontal relief, broad ethmoid-frontal depression, strongly developed supraoccipital crest, bar-like nasal, jaw teeth arranged in a single row, posterior preopercular margin apparently entire, rounded and molariform lower pharyngeal teeth, six branchiostegal rays, 24 (9+15) vertebrae, moderately reduced neural spine of the first vertebra, parhypurapophysis absent, XI + 9 dorsal fin elements, III + 9 anal fin elements and 12 pectoral-fin rays. The comparative analysis of morphological and meristic features reveals that Bellwoodilabrus landinii n. gen., n. sp. possesses a combination of plesiomorphic and derived features, which is unique within the Labridae. Bellwoodilabrus landinii n. gen., n. sp. Represents the third valid species of the family Labridae described up to now from Monte Bolca. The morphofunctional analysis of the cranial and appendicular skeleton suggests that Bellwoodilabrus landinii n. gen., n. sp. was a benthic invertebrate feeder that inhabited the deep and calm settings along the northern coasts of the central Tethys. The evolutionary significance of the Eocene labrids from Monte Bolca is also discussed. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris.
Increased potential versatility in form and function of the feeding apparatus of cichlid fishes has led to a prodigious proliferation in the number of possible functional solutions to an increasing variety of biological problems. Optimal utilization of every conceivable trophic resource in lacustrine environments by just one fish family, the Cichlidae, has been achieved by eruptive evolutionary radiation within the characteristically cichlid body plan producing mechanisms which partition the diverse food resources with extraordinary efficiency therefore minimizing resource sharing. There is a direct relationship between the effectiveness of trophic resource exploitation and the functional integration of the cichlid body plan in which a minimum number of adaptive compromises are necessary to evolve optimal anatomical solutions by rapidly realizable changes
Anatomical data presented here reveal that cichlids possess a specific kind of mosaic in which the basic percoid jaw apparatus permits unparalleled optimal adaptations by simple morphogenetic changes while unique and dramatically diverse patterns of muscular coordination involving degrees of synchrony and extensive modulating capabilities of antagonistic muscle groups have been discovered electromyographically. At the same time the highly integrated pharyngeal jaw apparatus is sufficiently specialized providing complete freedom for the jaws to evolve into refined collecting devices.
The exceptional evolutionary success of lacustrine cichlids demonstrates how rare and very specific kinds of biologically versatile morphological mosaics represent the best preadaptations for the ancestors of major new taxa. Given identical ecological conditions and temporal factors, a group of organisms possessing such rare mosaics, in which optimal biological versatility is realizable by simple evolutionary mechanisms, will dominate newly formed environments to the detriment of taxa not so endowed.
Pile perch were found to feed readily on single whole mussels. These were crunched by the massive pharyngeal teeth of the perch and swallowed completely without shell ejection. In the gut a mucous coating enveloped the fragmented shells protecting the mucosa from injury. The mucous envelope dissolved rapidly following defecation. X-rays of the intestine and sonic recording by hydrophone of the crunching sounds were used to follow digestion and trace the feeding frequency when browsing on a colony of mussels. At 10 °C, after 1 h of intensive feeding, the mussels took from 1 to 4 days to be completely digested; the shell fragments were unaffected by digestion. On a fixed photoperiod, feeding activity was confined to daylight hours except some exploratory browsing which occurred immediately prior to lights coming on.
This paper, dealing with the morphology (viz. structure, insertion areas, direction and, to a lesser degree, shape) of the head muscles of Haplochromis elegans, is the second study in a series on the head-morphology of this generalized Haplochromis species from the East-Africa Lakes Edward and George. The shape-descriptions of the skeletal elements, given in the first paper of the series (BAREL et al., 1976), have been used for an accurate definition of the position of the muscles. As well as dissection, graphical reconstructions from serial sections were necessary for an adequate description, especially of the small and complicated branchial muscles. The aim of the series is a basic description of the head-morphology of a generalized Haplochromis species suitable for comparative studies on the functional morphology of cichlid fishes. Therefore the muscle-descriptions deal with aspects relevant to functional morphology and generally do not enter upon questions of formal comparative morphology, viz. homology and related subjects.
The behaviour of Badis badis is similar, in general, both to that of “nandid” fishes and that of anabantoid fishes; trenchant differences also exist. It is impossible at this time, on behavioural evidence alone, to assess the relative importance of the behavioural findings. However, the remarkable and consistent agreement in the performance of the spawning embrace suggests a close relationship of Badis to anabantoid fishes rather than to the “nandids”.
The osteological studies confirm this hypothesis. Badis apparently split off from the ancestral anabantoids before they acquired the air-breathing adaptation. The osteological differences between Badis and the anabantoids stem chiefly from the modifications accompanying aerial respiration.
The egg of Badis badisis enclosed in an unusually tough sheath that is extremely adhesive. The egg itself lacks any special device for attaching. The larva has an adhesive organ at the tip of the yolk sac. The egg and the larva of Badis badis are thus unique among teleosts insofar as is known.
From these three lines of information we erect a new percoid family, Badidae, based on Badis Bleeker. This family appears to have descended from the proto-anabantoid stock.
Among piscivorous cichlids consistent differences have been recorded between ambush and pursuit hunters with respect to electromyographic, kinematic, pressure and behavioral profiles during prey capture by high speed inertial suction. Piscivorous cichlids possess a repertoire of at least two patterns of prey capture, each of which is characterized by an extreme regularity of the kinematic, pressure, electromyographic and behavioral profiles. The nature and locomotory behavior of the prey, visually analyzed by the predator during the prestrike stalk, determine which of the two preprogrammed patterns is recruited. Agile and elusive prey invariably will elicit a preprogrammed motor output (stereotyped motor pattern) that produces the greatest suction velocities in both ambush and pursuit hunters. The greater the kinematic and suction velocities, the greater the overlap of the firing sequences of antagonistic muscle complexes. The opercular and branchiostegal apparati function as an exceedingly effective anti-backwash device, damping potential fluid oscillations within the oropharynx. Mastication occurs by triphasic movements and actions of muscles of the upper and lower pharyngeal jaws in both ambush and pursuit hunters. The lower pharyngeal jaw is acted upon by a force couple of which the fourth levator externus on one hand and the pharyngocleithralis externus and pharyngohyoideus on the other hand are the antagonistic components. Furthermore, the lower pharyngeal jaw is suspended by a muscular sling, the tension of which can be modified continuously. It is postulated that the switch from insectivorous to piscivorous feeding regimes (and perhaps vice versa) is accomplished by very minor structural and functional modifications, because the modulatory multiplicity and total range of repertories of the feeding machinery of the two trophic groups overlap significantly. Piscivorous cichlids may not have arisen by orthoselection in gradually-changing lineages, but represent the differential success of subsets from a random pool of speciation events. Adaptive features identified as characteristic for piscivory could have evolved in multiple and independent lineages at a punctuational mode and tempo.
Thesis (Ph. D.)--Stanford, 1951. Includes bibliographical references (leaves 166-178).
Liem, Karel F. (Museum of Comparative Zoology, Harvard University, Cambridge, Mass. 02138) 1974. Evolutionary strategies and morphological innovations: Cichlid pharyngeal jaws. Syst. Zool. 22:425–441 .—The percoid fish family Cichlidae possesses a phenomenal ability to colonize lakes and to diversify to an extent unmatched by any other vertebrate family in the presence of predator pressure and strong competition. The invading cichlids successfully occupy contiguous and occasionally overlapping adaptive zones and specialize progressively into diversified subzones, ramifying prodigiously and covering a breadth of total adaptation that would have been entirely unpredictable if we were aware only of the rudiments of the evolutionary process. This evolutionary avalanche can be attributed to the cooccurrence of a wide range of prospective adaptive zones in the lacustrine environment, and the presence of a unique morphological key innovation of maximum versatility. The new adaptive complex has been revealed in this study by electromyographic analysis synchronized with cineradiography of the cichlid pharyngeal jaw apparatus. The morphological novelty characterizing the family Cichlidae involves the development of: a synarthrosis between the lower pharyngeal jaws, a strategic shift of insertion of the two fourth levator externi muscles, and synovial joints between upper pharyngeal jaws and basicranium. This specialized, highly integrated key innovation enables the cichlids not only to transport (deglutination) but also to prepare food, freeing the premaxillary and mandibular jaws to evolve numerous specializations dealing with the collection of dramatically diverse foods. The functional integration of the innovation is so basic and its potential adaptive versatility so rich that it is maintained throughout the adaptive radiation even though numerous nondisruptive evolutionary changes do take place, providing prodigious opportunities for explosive evolution during the exploitation of rich resources of food in the lacustrine environment. The conversion of the preexisting elements into a new and significantly improved cichlid adaptive complex of high selective value may have evolved by rapid steps under influence of strong selection pressure acting on the minor reconstruction of the genotype which is involved in evolutionary changes of the pertinent ontogenetic mechanisms. Such relatively simple evolutionary processes are probably the cause for the general phenomenon that only slight reconstructions of existing structures are necessary for successful and rapid adaptation to drastic shifts of adaptive zones.
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