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Paleogeographic World maps. Permo-Triassic transition (245 Myr before present). There was a single landmass (Pangaea) with generally warm and slightly dry conditions in the northern (Laurasia) and southern parts (Gondwana). Nevertheless, eastern Pangaea received more moisture and the southern half of Gondwana suffered strong seasonal fluctuations of temperature (and probably of aridity). The western coast of the American continents and much of SE Asia were submerged under an epicontinental sea. Reptiles inhabited the land. A mass extinction had decimated diversity in the Permian seas. In this series of maps (Figs 5–8), submerged land areas (usually controversial or ignored in reconstructions) are based on distributions of marine and terrestrial organisms, including ammonites, belemnites, hermatypic corals, bivalves, foraminiferans, brachiopods, ostracods, bryozoans, arthropods, fishes, amphibians, reptiles and other vertebrates, as well as plants (based on MacKerras, 1970; Heirtzler, 1976; Kurte ́ n, 1976; Hallam 1973, 1981; Schuster, 1976, 1983; Pielou, 1979; Coney, 1982; Go ́ mez, 1982; Bussing, 1985; Seyfried & Sprechman, 1985; Alvarado, 1988. Climatic reconstructions and plate tectonic maps follow Cox, 1974; Barron & Washington, 1982; Condie, 1982; Hay, Behensky, Barron & Sloan, 1982; Parrish & Curtis, 1982; McKenzie, 1986; Alvarado, 1988; van der Voo, 1988; Horgan, 1989; Gyllenhaal et al. , 1991; Parrish, Ziegler & Scotese, 1982; Patzkowsky et al. , 1991; Piccoli et al. , 1991; Wang & Chen, 1991). Circles: centres of current Peripatid geographic ranges. Squares: centres of current Peripatopsid geographic ranges. Shaded areas emerged land.
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A cladistic analysis places the Onychophora between Polychaeta and Arthropoda. The ‘Uniramia‘concept is not supported. No justification was found for either onychophoran family to be considered ancestral. A cladogram of fossil genera indicates the common ancestor to have long oncopods, armoured plates and an annulated body. Later forms show adaptat...
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... The resulting selection for a low cost : benefit ratio explains their predatory behaviour, compared with other feeding habits that provide less energy (see Brusca & Brusca, 1990). There is evidence that Peripatus acacioi Marcus & Marcus may be undernourished in nature (Campiglia & Lavallard, 1989), suggesting the importance of feeding restrictions. Captive Peripatoides gilesii Spencer have fed in daylight (van der Lande, 1978). If onychophorans feed during daytime in nature, it may represent an adaptation to moist temperate microhabitats with many day-active prey (Ruhberg & Nutting, 1980). Nocturnal pulmonate molluscs sometimes become active during daytime hours when rain increases the atmospheric humidity (personal observations) and some onychophorans may behave similarly. It has been suggested (Robison, 1985) that the development of adhesive glands took place on land, because the adhesive substance would have been inoperative in the sea. In fact, the adhesive substance of E. biolleyi dissolves quickly in sea water, dries in air after a few seconds, and remains operative for hours in fresh water (Monge-Na ́ jera, in preparation). Adhesive glands are probably modified crural glands (see Ruhberg & Storch, 1977), although Anderson (1966) disagreed. Apparently no model has been published about the evolutionary development of onychophoran adhesive glands, which are used both to capture prey and for defence. A hypothesis that may encourage future analysis is that the original function was defence. This is suggested because chemical defence is widespread in animals, including many invertebrates (see Brusca & Brusca, 1990) and mammals (Eisenberg, 1981), while a hunting adhesive is only known in onychophorans (some arachnids use adhesive, although the mechanism is different; see Lavallard & Campiglia, 1971). Ancestral onychophorans might have secreted from their crural glands a viscous substance which interfered with the mandibular action of small predators. In this way, the original apparatus could be functional from an early stage, requiring only improvements in the viscosity, amount and distance that the substance could be expelled. This defensive substance would in turn also be useful for hunting, if the original condition consisted of capturing some prey directly with the mandibles, as still occurs when onychophorans handle small prey. The adhesive substance probably allowed the entanglement of larger and therefore more nutritious prey. The glands produce an adhesive substance which, when expelled, is guided with the help of a pair of eyes with large chitinous lenses and a well- developed retinal layer. Although onychophoran vision was traditionally thought to be poor (Cue ́ not, 1949), it is noted that the ability to distinguish leg joints and fangs mentioned by Read & Hughes (1987) indicates otherwise. Food is digested extra-corporally with the help of enzymes in saliva produced by modified nephridia (Buxton, 1913; Storch, Alberti & Ruhberg, 1979). Cave dwelling organisms often have elongated appendages, lack eyes and cuticular pigmentation and occur in small and isolated geographic ranges. In tropical and subtropical areas they probably evolved from non-troglobitic ancestors living in dark and humid habitats (Holsinger, 1988). This suggests that the Onychophora, all adapted to dark humid microhabitats, are well suited to produce troglobitic species. However, only two are known: the peripatopsid Peripatopsis alba of South Africa Lawrence, 1931 and the peripatid Speleoperipatus spelaeus Peck, 1975 from Jamaica. Typhloperipatus williamsoni Kemp, 1914 from India and Tasmanipatus anophthalmus Ruhberg, Mesibov, Briscoe & Tait, 1991 from Tasmania, both of which live under forest litter, are eyeless; the former retained normal pigmentation, but pigmentation is reduced in T. anophthalmus. Some Peripatoides indigo Ruhberg, 1985 and Peripatoides novaezealandiae Hutton, 1876 from New Zealand have been found in caves but do not have troglobitic characters (Ruhberg, 1985a; Newlands & Ruhberg, 1978). Troglobitic ecosystems depend on external energy and often sustain only small populations (Holsinger, 1988). They often have species with low respiratory rates which are slower and less aggressive than related non-cave species (Lawrence, 1962). The population size of both S. spelaeus and P. alba was very small (Lawrence, 1931; Peck, 1975). The implications of the biogeographic analysis are presented separately for each family (Figs 5–8). Peripatopsidae. The occurrence of Peripatopsidae in New Guinea and adjacent islands (but not New Zealand), as well as in eastern Australia and Tasmania, must represent a post-Pliocene colonization because those areas were submerged in the Oligocene-Pliocene (Fig. 8B, references in figure caption). Chilean peripatopsids probably reached their current range after the early Cretaceous, because the area which is currently Chile was previously submerged (see Figs 6 and 7; sources stated in Fig. 5). The separation of peripatopsid populations which originally inhabited southern Gondwana began not later than the Early Cretaceous, when South Africa became separated by a water gap (Fig. 7). A terrestrial connection remained between South America and Australia until the end of the Cretaceous via Antarctica (but see below). Peripatidae. The exact range of the Onychophora in Southeast Asia is not known, but current data indicate that at least part of the area may have been submerged in the Oligocene-Pliocene (Fig. 8) suggesting a later colonization. The southern half was submerged in the Lower Cretaceous (Fig. 7) and must have been colonized after that time. If the Mexican, Central American and Antillean Onychophora have a South American origin, as is widely believed (see Cue ́ not, 1949), these areas must have been reached after the Early Cretaceous for the same reason (Figs 7 and 8). According to the reconstruction presented here, Mesoperipatus Evans lost any remaining terrestrial contact with South American onychophorans after the Lower Cretaceous (Fig. 7). The time of separation for the Asian population is more difficult to assess. The last terrestrial connection between a joined South America–Africa landmass and Asia, occurred in the early Jurassic via North America. Another possibility is that Asian onychophora originated in the early Jurassic, when India was in contact with South American and Africa. If such was the case, the Indian onychophorans (Figs 6–8) were carried north and colonized Southeast Asia when India collided with ...
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... of oncopodophores. One hypothesis is that they changed from exposed life on the marine substratum to new microhabitats with reduced space, such as tunnels, crevices or even sponge canals (although reconstructions show Aysheaia crawling on the outside of sponges (Whittington, 1978), a lack of armour would better suit life inside the canal system of the sponge). Some predictions of the reduced space hypothesis are: (1) elimination of structures hindering forward movement, such as spines and prominent plates, (2) reduction of oncopod length, and (3) increase in body flexibility. Current data on Aysheaia, Helenodora and Onychophora do not allow rejection of this hypothesis (Manton, 1958; Thompson & Jones, 1980; Robison, 1985). In small spaces where many predators cannot follow, a rigid spiny armour appears both unnecessary and a hindrance (see Manton, 1958). The loss of metameric internal organization of the body is associated with the functionality of a fluid skeleton (Boudreaux, 1979), which is useful for life in tunnels (Manton, 1958). The evolution of internal fertilization and a direct life cycle is frequent in marine invertebrates with vagile adults which live in unstable environments (Brusca & Brusca, 1990). This could suggest that internal fertilization occurred in tidal zone oncopodophores and that it favoured land colonization for onychophorans, because direct gamete transfer provides an appropriate environment even out of water (see Brusca & Brusca, 1990). Accompanying internal fertilization, some crural glands and nephridia became modified as accessory genital glands (Purcell, 1900; Ruhberg & Storch, 1978). Similar structures occur in Heterotardigrada (Renaud-Mornant, 1982). Manton (1958) insisted that a hard exoskeleton never evolved in the Onychophora because the ability to change body shape was favourably selected as an adaptation to move through reduced spaces. This capacity, related to the absence of striated muscle (which does not bend easily) allows them to escape from predators and unfavourable conditions and implied that a tentorium could not develop (Manton, 1958, 1973). From those ideas it can be hypothesized that one of the prerequisites for a rigid mandibular apparatus with a tentorium has not been developed in the group. Without a tentorium, strong predatory mandibles cannot function, explaining why adhesive glands are particularly useful to dominate the prey and for defence. The maintenance of a flexible body imposes severe limitations on body size, precision of movements, defence and speed (Brusca & Brusca, 1990), a generalization which fits the Onychophora (Appendices 1–5). The stages that onychophorans may have followed during adaptation to land are illustrated by some anomuran and brachyuran decapods: some burrow to avoid desiccation; others to control blood density and drink; additionally to these adaptations, others use water-absorbing structures (see Barrington, 1979). Onychophoran adaptations correspond to the most advanced decapod stage (see Manton & Ramsay, 1937; Campiglia & Maddrell, 1986; Campiglia & Lavallard, 1978; Barrington, 1979; Ruhberg & Nutting, 1980). Perhaps burrowing occurred in late Cambrian oncopodophores (as suggested by loss of armouring) and was used in the intertidal zone to prevent desiccation during low tides. Burrowing is a key survival factor in living onychophorans, which are thought to be unable to make tunnels, although this has not been formally studied (see Ruhberg, 1985a for a review). Experiments in progress indicate that E. biolleyi is incapable of making burrows even in soft soil (Monge- Na ́ jera, unpublished observation). Because the ancestors of onychophorans lived in shallow marine environments, they may have adapted to land via the intertidal zone. A transitional freshwater stage could also be hypothesized, because the adhesive substance functions when experimentally ejected under freshwater (see below). From Barrington (1979), I have extracted the following characters that indicate a direct sea-land transition: (1) development of major water retention mechanisms, (2) water drinking behaviour, (3) ultrafiltration, (4) high surface permeability, (5) high blood osmotic pressure and (6) uricotely. All occur in the Onychophora (see Manton & Ramsay, 1937; Campiglia & Maddrell, 1986; Campiglia & Lavallard, 1978; Barrington, 1979; Ruhberg & Nutting, 1980) and clearly suggest that they adapted to terrestrial life via the littoral zone. Since the first arthropods were marine (Shear & Kukalova ́ -Peck, 1990), and the Tardigrada are also aquatic (Brusca & Brusca, 1990), the Onychophora probably occupied land independently of the Arthropoda (Fig. 1). The cladogram suggests that they originated before the terrestrial arthropods (Fig. 1), which appeared in the late Ordovician (Shear & Kukalova ́ -Peck, 1990). Fossil oncopodophores have only been found in northern continents, while Recent onychophorans have a Tropical-Austral distribution (Fig. 5). Location on maps of the corresponding geologic periods shows that marine oncopodophores inhabited shallow waters in the subcontinental areas of Baltica, China and North America (Cambrian tropical and temperate belts) and later, in North America and Europe (Carboniferous tropical belt; Monge- Na ́ jera, in preparation). On land, a waxy body cover that reduces desiccation is not advantageous in organisms that experience daily temperature changes (Barrington, 1979), a fact that could suggest that onychophorans, which lack an external wax layer, adapted to land in a habitat characterized by strong daily fluctuations in temperature. On the other hand, Ruhberg & Nutting (1980) suggested that onychophorans colonized land in a temperate region, because cooler climates have water richer in oxygen and reduce xeric stress. Both hypotheses deserve elaboration and testing. Terrestrial gas exchange also posed a problem, which was solved through the development of tracheae. Onychophoran tracheae must be analogous to those of the Arthropoda (Fig. 1). Nevertheless, histological evidence needs to be obtained, because Manton (1967) mentioned that onychophoran tracheae resemble those of some centipedes. The independent development of similar structures is to be expected because onychophoran tracheae are also similar to cutaneous invaginations found in terrestrial polychaetes (Marcus, 1937; see also Bicudo & Campiglia, 1985). No branchiae have been found in fossil oncopodophores although body evaginations in Onychodictyon (see illustration in Hou et al. , 1991) might have been respiratory structures. Thus it is more likely that the tracheae used on land evolved secondarily after aquatic cutaneous gas exchange. There was no tendency towards mechanical protection from desiccation which is chiefly avoided through nocturnal and photonegative behaviour (Manton & Ramsay, 1937; Holliday, 1942; Morrison, 1946b; Endro ̈ dy-Younga & Peck, 1983; Lavallard et al. , 1975). As a result, onychophorans are restricted to moist habitats and some populations may easily become isolated in small areas (Lavallard et al. , 1975; van der Lande, 1978; Morera-Brenes & Monge- Na ́ jera, 1990; Mesibov & Ruhberg, 1991). Habitat restriction has been found to favour inbreeding adaptations in other organisms (Ram ́rez, 1987), as discussed later. In onychophorans, the lack of a strong protection against desiccation imposes significant restrictions. Food needs to be obtained within a very limited time (a few hours per day) and space (nearby moist microhabitat). The resulting selection for a low cost : benefit ratio explains their predatory behaviour, compared with other feeding habits that provide less energy (see Brusca & Brusca, 1990). There is evidence that Peripatus acacioi Marcus & Marcus may be undernourished in nature (Campiglia & Lavallard, 1989), suggesting the importance of feeding restrictions. Captive Peripatoides gilesii Spencer have fed in daylight (van der Lande, 1978). If onychophorans feed during daytime in nature, it may represent an adaptation to moist temperate microhabitats with many day-active prey (Ruhberg & Nutting, 1980). Nocturnal pulmonate molluscs sometimes become active during daytime hours when rain increases the atmospheric humidity (personal observations) and some onychophorans may behave similarly. It has been suggested (Robison, 1985) that the development of adhesive glands took place on land, because the adhesive substance would have been inoperative in the sea. In fact, the adhesive substance of E. biolleyi dissolves quickly in sea water, dries in air after a few seconds, and remains operative for hours in fresh water (Monge-Na ́ jera, in preparation). Adhesive glands are probably modified crural glands (see Ruhberg & Storch, 1977), although Anderson (1966) disagreed. Apparently no model has been published about the evolutionary development of onychophoran adhesive glands, which are used both to capture prey and for defence. A hypothesis that may encourage future analysis is that the original function was defence. This is suggested because chemical defence is widespread in animals, including many invertebrates (see Brusca & Brusca, 1990) and mammals (Eisenberg, 1981), while a hunting adhesive is only known in onychophorans (some arachnids use adhesive, although the mechanism is different; see Lavallard & Campiglia, 1971). Ancestral onychophorans might have secreted from their crural glands a viscous substance which interfered with the mandibular action of small predators. In this way, the original apparatus could be functional from an early stage, requiring only improvements in the viscosity, amount and distance that the substance could be expelled. This defensive substance would in turn also be useful for hunting, if the original condition consisted of capturing some prey directly with the mandibles, as still occurs when onychophorans handle small prey. The adhesive substance probably allowed the ...
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... 6. Early Jurassic (194 Myr before present). The separation of Laurasia and Gondwana has begun, with a connection remaining via the Iberian Peninsula. Many areas, including much of Europe, were submerged, but eastern Asia was connected by land to North America. The climate was warm and dry and dinosaurs and flying reptiles inhabited the land (sources and symbols as in Fig. 5).
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... 7. A, Lower Cretaceous (116 Myr before present). The connection of North America with East Asia, and the proximity of North America to Gondwana via Africa, may explain some of their present biotic similarities. The pattern of epicontinental seas had changed and Africa became separated by water from India and Antarctica, while connected indirectly to them and to Australia by South America. In general, the climate was very warm and dry, conditions which would become harsher in the mid Cretaceous. B, Upper Cretaceous (87 Myr before present). North America was divided by sea into eastern and western landmasses. The western was connected to East Asia until late in the period, and the eastern connected to western Europe. Africa was composed of two large islands fully separated from Madagascar and India, a large island itself at about 72 Myr before present: a brief island connection existed between South and North America, via the Antilles, which were moving eastward. New Zealand separated from West Antarctica. The climate was, in general, very warm and dry (sources and symbols as in Fig. 5).
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... 8. A, Paleocene-Eocene (Tertiary) (59–40 Myr before present). The distribution of epicontinental seas changed significantly. Asia was connected with North America and Europe by what probably was an island arc. The Antilles were close to their current position and Central America was represented by another island arc. South America and Australia were separating from Antarctica (which was still forested). Much of Africa was submerged, but the northern part was in contact with the Iberian Peninsula. The relative position of India appears here as indicated by palaeomagnetic evidence (Condie, 1982), although fossil data indicate contradictory relationships: closer to Asia (animals: Hallam, 1981) and closer to South Africa (plants: Schuster, 1983). B, Oligocene-Pliocene (Tertiary) (28–3.4 Myr before present). There was a continuum of land uniting Asia, North America, Greenland and Europe, although there was still no direct connection between Europe and Asia. Island arcs connected South with North America, and Europe with Africa. India was rapidly approaching Asia and epicontinental seas covered great areas and may have even invaded the Amazon basin and more of Africa than shown here. Temperature and aridity fluctuated widely. In the Oligocene, plate collisions elevated the Himalayas and the Alps: the Miocene was a time of great vulcanism and increasing aridity, with forests being substituted by grasslands. In the Pliocene the temperatures fell significantly and the Central American Isthmus fully united South and North America (sources and symbols as in Fig. 5).
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... oncopodophores have only been found in northern continents, while Recent onychophorans have a Tropical-Austral distribution (Fig. 5). Location on maps of the corresponding geologic periods shows that marine oncopodophores inhabited shallow waters in the subcontinental areas of Baltica, China and North America (Cambrian tropical and temperate belts) There was a single landmass (Pangaea) with generally warm and slightly dry conditions in the northern (Laurasia) and ...
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... mass extinction had decimated diversity in the Permian seas. In this series of maps ( Figs 5-8), submerged land areas (usually controversial or ignored in reconstructions) are based on distributions of marine and terrestrial organisms, including ammonites, belemnites, hermatypic corals, bivalves, foraminiferans, brachiopods, ostracods, bryozoans, arthropods, fishes, amphibians, reptiles and other vertebrates, as well as plants (based on MacKerras, 1970;Heirtzler, 1976;Kurté n, 1976;Hallam 1973Hallam , 1981Schuster, 1976Schuster, , 1983Pielou, 1979;Coney, 1982;Gó mez, 1982;Bussing, 1985;Seyfried & Sprechman, 1985;Alvarado, 1988. Climatic reconstructions and plate tectonic maps follow Cox, 1974;Barron & Washington, 1982;Condie, 1982;Hay, Behensky, Barron & Sloan, 1982;Parrish & Curtis, 1982;McKenzie, 1986;Alvarado, 1988;van der Voo, 1988;Horgan, 1989;Gyllenhaal et al., 1991;Parrish, Ziegler & Scotese, 1982;Patzkowsky et al., 1991;Piccoli et al., 1991;Wang & Chen, 1991). ...
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... implications of the biogeographic analysis are presented separately for each family (Figs 5-8). ...
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... Myr before present). The separation of Laurasia and Gondwana has begun, with a connection remaining via the Iberian Peninsula. Many areas, including much of Europe, were submerged, but eastern Asia was connected by land to North America. The climate was warm and dry and dinosaurs and flying reptiles inhabited the land (sources and symbols as in Fig. ...
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... early Cretaceous, because the area which is currently Chile was previously submerged (see Figs 6 and 7; sources stated in Fig. 5). The separation of peripatopsid populations which originally inhabited southern Gondwana began not later than the Early Cretaceous, when South Africa became separated by a water gap (Fig. 7). A terrestrial connection remained between South America and Australia until the end of the Cretaceous via Antarctica (but see ...
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... of two large islands fully separated from Madagascar and India, a large island itself at about 72 Myr before present: a brief island connection existed between South and North America, via the Antilles, which were moving eastward. New Zealand separated from West Antarctica. The climate was, in general, very warm and dry (sources and symbols as in Fig. 5). Figure 8. A, Paleocene-Eocene (Tertiary) (59-40 Myr before present). The distribution of epicontinental seas changed significantly. Asia was connected with North America and Europe by what probably was an island arc. The Antilles were close to their current position and Central America was represented by another island arc. South ...
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... widely. In the Oligocene, plate collisions elevated the Himalayas and the Alps: the Miocene was a time of great vulcanism and increasing aridity, with forests being substituted by grasslands. In the Pliocene the temperatures fell significantly and the Central American Isthmus fully united South and North America (sources and symbols as in Fig. 5). Figure 9. The technique of retrovicariance biogeography. Area cladograms are useful to produce phylogenic hypotheses. In this imaginary example, geologic evidence indicates that areas A and B were joined more recently, while area C had separated earlier (A). The phylogenetic relationship of three taxa, x, y and z, is unknown (B), but ...
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... biogeographic model (Figs 5-8) suggests that the two extant families, Peripatopsidae and Peripatidae, were fully distinct and had wide longitudinal distributions in Triassic-Jurassic times. This contradicts Vachon (1953,1954), who did not have access to the detailed paleogeographical information now available. ...
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... applying the retrovicariant procedure to the areas inhabited by onychophorans (Fig. 10A) in accordance with the sequence of geographic separations shown in Figures 5-8, a phylogenetic hypotheses for both families was produced (Fig. 10). The resulting cladogram (Fig. 10B) indicates for the Peripatidae a common ancestor for the taxa of Equatorial Africa and the Neotropics (contradicting Purcell, 1900), while the Asian taxa represent their sister group which separated earlier. ...
Citations
... They predominantly inhabit permanently moist microhabitats to avoid desiccation (Giribet and Edgecombe, 2020;Oliveira et al., 2012). Velvet worms are particularly notable for their unique prey capture mechanism (Baer et al., 2017;Baer et al., 2019;Benkendorff et al., 1999;Haritos et al., 2010), strong biogeographic affinities Monge-Nájera, 1995;Murienne et al., 2014), and their remarkable diversity of reproductive strategies. Ranging from oviparity, through ovoviviparity, to placental viviparity, their reproductive modes have been hypothesized to be involved in their dispersal and subsequent radiation, particularly on Caribbean islands (Anderson, 1973;Baker et al., 2021;Mayer et al., 2015). ...
... They are softbodied, many-legged, animals that inhabit permanently moist microhabitats. The phylum is divided into two families: the circumtropical Peripatidae, and the temperate Gondwanan Peripatopsidae Giribet and Edgecombe 2020) that diversified before the breakup of Gondwana and display strong biogeographic affinities (Monge-Nájera 1995;Murienne et al. 2014;Giribet et al. 2018). Onychophora is particularly notable for their distinctive prey capture mechanism in which they secrete a glue from two modified, anterior appendages to entangle prey (Benkendorff et al. 1999;Haritos et al. 2010;Baer et al. 2017;Baer et al. 2019). ...
Genome assemblies are growing at an exponential rate and have proved indispensable for studying evolution but effort has been biased toward vertebrates and arthropods with particular focus on insects. Onychophora or velvet worms are an ancient group of cryptic, soil dwelling worms noted for their unique mode of prey capture, biogeographic patterns, and diversity of reproductive strategies. They constitute a poorly understood phylum of exclusively terrestrial animals that is sister group to arthropods. Due to this phylogenetic position, they are crucial in understanding the origin of the largest phylum of animals. Despite their significance, there is a paucity of genomic resources for the phylum with only one highly fragmented and incomplete genome publicly available. Initial attempts at sequencing an onychophoran genome proved difficult due to their large genome size and high repeat content. However, leveraging recent advances in long read sequencing technology, we present here the first annotated draft genome for the phylum. With a total size of 5.6Gb, the gigantism of the Epiperipatus broadwayi genome arises from having high repeat content, intron size inflation, and extensive gene family expansion. Additionally, we report a previously unknown diversity of onychophoran hemocyanins that suggests the diversification of copper-mediated oxygen carriers occurred independently in Onychophora after its split from Arthropoda, parallel to the independent diversification of hemocyanins in each of the main arthropod lineages.
... Onychophorans, also known as "velvet worms", have fascinated small groups of naturalists in every generation: they seem to be the only invertebrate phylum without extant aquatic species (Monge-Nájera 2021) and have many unusual characteristics: some species feed their embryos through placentas that are analogous to those of mammals; secretiveness, which make them particularly hard to find in the field, and it is thought that their past and current diversity are greatly underestimated (Oliveira et al. 2012). There are less than 200 named species, but this is thought to be a fraction of their true biodiversity, and their current distribution, in six disjunct areas that include Latin America, tropical and Southern Africa, Southeast Asia and Oceania, can be explained by range fragmentation during the break-up of Pangea (Vachon 1954, Monge-Nájera 1995. The oldest fossils are of tiny marine species with long legs that were protected by spikes and scutes, while extant species are all terrestrial, have short legs, lack spikes and scutes, and range from a few millimeters to 20 centimeters in length. ...
... The general trend shows that, decade after decade, there are three questions that mostly interest researchers: (1) the age of the group, which is closely related to the basal taxa of the main invertebrate phyla and had its beginnings in Cambrian marine mudflats (Monge-Nájera 1995; Monge-Nájera and Hou 2002); (2) their presence in three tropical and three temperate regions, all of them isolated from each other, and reflecting some ancient continental distribution (Vachon 1954;Monge-Nájera 1995;Murienne et al. 2014); and (3) their development, marked by embryos that, in some species, grow in a factory-like production chain in which they are connected to the mother by a placenta, an organ absent in most invertebrates (Monge-Nájera 1995;Janssen et al. 2018). ...
... The general trend shows that, decade after decade, there are three questions that mostly interest researchers: (1) the age of the group, which is closely related to the basal taxa of the main invertebrate phyla and had its beginnings in Cambrian marine mudflats (Monge-Nájera 1995; Monge-Nájera and Hou 2002); (2) their presence in three tropical and three temperate regions, all of them isolated from each other, and reflecting some ancient continental distribution (Vachon 1954;Monge-Nájera 1995;Murienne et al. 2014); and (3) their development, marked by embryos that, in some species, grow in a factory-like production chain in which they are connected to the mother by a placenta, an organ absent in most invertebrates (Monge-Nájera 1995;Janssen et al. 2018). ...
Onychophorans are worms of Cambrian origin that have unclear relationships with annelids, tardigrades and arthropods; they have their own phylum and are remarkable for capturing their prey with an adhesive net that forms in a fraction of a second, and for having species in which the young are fed through a placenta. There is no quantitative review of any trends in their study, so the purpose of this article is to review 150 years of onychophorology using bibliometric tools. We used the database Scopus, for the period 1876 through 2021, identified 538 valid articles about these worms, and analyzed them with the software VOSviewer, to identify countries, subjects and historical trends, as well as which fields need strengthening to understand and protect them. We found that, when corrected for country population size, the most productive countries are Sweden, Australia and Costa Rica; but by raw numbers, USA, Germany, and the UK have the most articles and citations in Scopus. Most work has been done on their Cambrian origin and phylogenetic relationships with other invertebrates; their geographic distribution; and their embryological development. Conservation, ecology and behavior have been neglected and offer the best chance for innovation. Some low-income countries are rich in onychophoran species and have the greatest urgency of conserving them, but lack the resources for this, opening opportunities for international collaboration.
... While we cannot rule for or against the possibility of colonization via GAARlandia with our chronogram, we note that we were unable to include samples from other Caribbean islands (e.g., Jamaica, Hispaniola), and as such our results may change with denser taxonomic sampling. Another plausible mechanism for the presence of peripatids on Caribbean islands is rafting via a sweepstakes scenario, possibly as a result of tropical storms, a scenario proposed by Monge-N ajera (1995). ...
... But within Neopatida, over-water dispersal--at least over moderately short distances--seems to have occurred multiple times to oceanic Caribbean islands and probably to the Galapagos (although some have argued that the occurrence of the Galapagos species is a human introduction, no one has demonstrated it [Espinasa et al. 2015]). This discrepancy is striking and begs for a biological explanation, which remains elusive given the generally limited understanding of many basic aspects of onychophoran biology, such as survival ability in sea water (see Monge-N ajera et al. 1993;Monge-N ajera 1995). ...
Onychophora (“velvet worms”) are charismatic soil invertebrates known for their status as a “living fossil”, their phylogenetic affiliation to arthropods, and their distinctive biogeographic patterns. However, several aspects of their internal phylogenetic relationships remain unresolved, limiting our understanding of the group’s evolutionary history, particularly with regard to changes in reproductive mode and dispersal ability. To address these gaps, we used RNA sequencing and phylogenomic analysis of transcriptomes to reconstruct evolutionary relationships and infer divergence times within the phylum. We recovered a fully resolved and well-supported phylogeny for the circum-Antarctic family Peripatopsidae, which retains signals of Gondwanan vicariance and showcases the evolutionary lability of reproductive mode in the family. Within the Neotropical clade of Peripatidae, though, we found that amino acid-translated sequence data masked nearly all phylogenetic signal, resulting in highly unstable and poorly supported relationships. Analyses using nucleotide sequence data were able to resolve many more relationships, though we still saw discordant phylogenetic signal between genes, probably indicative of a rapid, mid-Cretaceous radiation in the group. Finally, we hypothesize that the unique reproductive mode of placentotrophic viviparity found in all Neotropical peripatids may have facilitated the multiple inferred instances of over-water dispersal and establishment on oceanic islands.
... In the field of conservation, the finding of a single large aggregation in New Zealand (Harris, 1991) and an unconfirmed estimate that the population of a single species reached millions, led to the unjustified generalization that these animals "are not rare" (Mesibov, 1998), an error that can lead to dangerous implications for conservation (Monge-Nájera, 1995). ...
... This decade was also marked by the first "modern synthesis" that proposed evolutionary explanations for the origin of all known onychophoran characteristics and summarized their history since the Cambrian, including anatomy, physiology, behavior, distribution, reproduction and systematics (Monge-Nájera, 1995). ...
... In the field of conservation, the finding of a single large aggregation in New Zealand (Harris, 1991) and an unconfirmed estimate that the population of a single species reached millions, led to the unjustified generalization that these animals "are not rare" (Mesibov, 1998), an error that can lead to dangerous implications for conservation (Monge-Nájera, 1995). ...
... This decade was also marked by the first "modern synthesis" that proposed evolutionary explanations for the origin of all known onychophoran characteristics and summarized their history since the Cambrian, including anatomy, physiology, behavior, distribution, reproduction and systematics (Monge-Nájera, 1995). ...
Velvet worms, or onychophorans, are animals of extraordinary importance in the study of evolution. This is the first history of their study. They were described by Lansdown Guilding (1797-1831). This paper identifies the landmarks of their study, in a worldwide level, for almost 200 years. The beginning, 1826-1879, was based on describing their anatomy with light miscroscopy, mostly by famous French naturalists such as Milne-Edwards and Blanchard. In 1880-1929 peiord, work concentrated in anatomy, physiology, behavior, biogeography and ecology, but the most important work was Bouvier`s mammoth monograph. The next period, 1930-1979, was important for the discovery of Cambrian species; Vachons explanation of how ancient distribution defined the existence of two families; Pioneer DNA and electron microscopy from Brazil; and primitive attempts at systematics using embryology or isolated anatomical characteristics. Finally, the 1980-2020 period, with research centered in Australia, Brazil, Costa Rica and Germany, is marked by an evolutionary approach to everything, from body and behavior to distribution; for the solution of the old problem of how they form their adhesive net and how the glue works; the reconstruction of Cambrian onychophoran communities, the first experimental taphonomy; the first countrywide map of conservation status (from Costa Rica); the first model of why they survive in cities; the discovery of new phenomena like food hiding, parental feeding investment and ontogenetic diet shift; and for the birth of a new research branh, Onychophoran Etnobiology, founded in 2015
... However, not all taxa at low taxonomic resolution are cosmopolitan. The phylum Onychophora (velvet worms), for example, inhabits the tropics, while the microinvertebrate phylum Loricifera (brush heads) await confirmation of their distribution (Monge-Najera, 1995;Kristensen, 2002). ...
The worldwide distribution of microinvertebrates on glaciers, the coldest biome, is poorly known. Owing to their tolerance to hostile conditions, small size and dispersal abilities, nematodes, tardigrades and rotifers are considered cosmopolitan and together inhabit various ecosystems. In this study, we investigated their global distribution in cryoconite holes – a type of freshwater reservoir forming directly in the glacial ice that creates biodiversity hotspots on glaciers. We analysed cryoconite samples (using classical microscopic observations and environmental DNA metabarcoding) from 42 glaciers located around the world (the Arctic, Subarctic, Scandinavia, the Alps, the Caucasus, Siberia, Central Asia, Africa, South America and Antarctica), as well as using literature data. Samples from Antarctic, Karakoram and the Alps were analysed using next‐generation sequencing (NGS) and classical observations under microscopes, while all other samples were analysed by microscope alone. Three general outcomes were found: (1) tardigrades and rotifers represented the most common invertebrates in cryoconite holes; (2) tardigrades and rotifers often coexisted together, with one or the other dominating, but the dominant taxon varied by region or by glacier; (3) nematodes – the most abundant, hyperdiverse and widespread metazoans on Earth, including in environments surrounding and seeding glacial surfaces – were consistently absent from cryoconite holes. Despite the general similarity of environmental conditions in cryoconite holes, the distribution of tardigrades and rotifers differed among glaciers, but not in any predictable way, suggesting that their distribution mostly depended on the random dispersal, extreme changes of supraglacial zone or competition. Although nematodes have been found in supraglacial habitats, cryoconite hole environments seem not to provide the necessary conditions for their growth and reproduction. Lack of physiological adaptations to permanently low temperatures (~0°C) and competition for different food resources in the cryoconite hole environment may explain the absence of nematodes in cryoconite holes.
... Onychophora are ancient Panarthropod animals with soft bodies, lobopodial legs with claws and a peculiar hunting strategy by which they eject glue to capture prey (Monge-Najera 1995). The group has 201 species distributed within Peripatidae (81 species) and Peripatopsidae (120 species), 20 of which are considered nomina dubia; however, the biodiversity of these species is far from established (Oliveira et al. 2020). ...
The diversity of Onychophora is poorly studied, despite there being nearly 200 described species divided in two families: Peripatidae and Peripatopsidae. Peripatid velvet worms are found mainly in the Neotropical region. The low morphological diversity in Peripatidae is an obstacle to determining its taxonomy, and chromosomal analyses can help clarify this. The aim of this work was to chromosomally analyze one species of Epiperipatus from Mato Grosso do Sul, Brazil. Conventional staining and telomeric fluorescent in situ hybridization (FISH) were performed with the gonads of three males of Epiperipatus sp. The specimens showed 2n♂ = 73, the largest diploid number found in Onychophora to date, with the majority of chromosomes acro/telocentrics and the largest element submetacentric. The FISH marked the telomeric region of all elements and revealed one Interstitial Telomeric Site (ITS) on the proximal region of the long arm large submetacentric chromosome. The absence of male meiosis and female cell division in the analyzed specimens prevented us from determining whether the unpaired large submetacentric is a sex chromosome, which could lead to the description of a rare sex chromosome system (SCS) in Onychophora, or a case of fusion between autosomes. In either case, the presence of ITS is a clear indication of chromosomal fusion.
... Costa Rican onychophorans have been placed within this group. Even though Costa Rican onychophorans have been studied in the last few years (Morera-Brenes, Monge-Nájera, & Sáenz, 1988; Monge-Nájera, Barrientos, & Aguilar, 1993;Monge-Nájera, 1995, Mora, Herrera, & León, 1995Monge-Nájera, 1996 For instance, Peripatidae lacks proper taxonomic characters that could be used to identify them. Therefore, progress in morphology has been slow (Read, 1988a(Read, , 1988bOliveira et al., 2012a;Sampaio-Costa, Amazonas-Chagas & Pinto-da-Rocha, 2018). ...
Introduction:
Neotropical onychophoran taxonomy and diversity has been poorly investigated. Recent studies have discovered problems in species classification: they have questioned the accepted genera and the actual number of species. This is true in Costa Rica, where several unidentified species have been reported.
Objective:
The objective of this investigation was to evaluate the occurrence of the accepted genera in this country, and to describe a new genus and species from Central America.
Methods:
In 2017, we collected one onychophoran in the Keköldi Indigenous Reserve in Talamanca, Limón, Costa Rica. The specimen gave birth to several offspring. Therefore, seven organisms were analyzed. Light microscopy was used to observe the gross morphology in all samples. The detailed morphology was studied in the biggest specimen with scanning electron microscopy; after that, we performed a phylogenetic analysis with the corresponding sequence of COI.
Results:
According to our results, a new genus and species of giant onychophoran was found. The genus was identified by its giant size, apical piece of seven scale ranks, large conical primary papillae, dorso-median furrow flanked by two-three accessory papillae, the absence of hyaline organs and a marked sexual dimorphism with respect to the number of legs. The new species presents a particular head pattern, as well as novel structures like cephalic papillae, accessory papillae with rudimentary apical pieces, and a lack of antennal chemoreceptors. Phylogenetic analysis rendered our genus as monophyletic and includes Peripatus solorzanoi, which is grouped within the Central American clade.As our species is clustered inside the Costa Rica-Panamanian group, it is not related to the Caribbean Island nor Guyanan Shield samples, home of Epiperipatus and Peripatus respectively. Therefore, we suggest that those genera do not occur in Central America, and a new genus exists: Mongeperipatus, gen. nov.
Conclusion:
We concluded that Costa Rica is home to a diversity of undescribed onychophorans that requires specific studies to help clarify the taxonomy and evolutionary relationships of the group to justify their protection.
... For decades, most authors have aligned with the idea that they are endangered because of their small populations and high susceptibility to habitat modification (Wells et al., 1983;Mesibov & Ruhberg, 1991;New, 1995;Vasconcellos et al., 2004). However, others have found that they survive forest fires (Mesibov & Ruhberg, 1991), volcanic eruptions (Barquero-González et al., 2016b), deep habitat urbanization (Barrett et al., 2016;Monge Nájera, 2018) and even the largest mass extinctions in the planet's history (Monge-Nájera, 1995). The secret to their extraordinary survival seems to be that, like dytiscid beetles, cave crickets, and soil burrowing cockroaches, they can hide underground (Lavallard, Campiglia, Álvarez & Valle, 1975;Beasley-Hall, et al., 2018); in fact, burrowing has been a key factor in their evolution since the Cambrian (Monge-Nájera, 1995). ...
Introduction: Charismatic species, like the panda, play an important role in conservation, and velvet worms arguably are charismatic worms. Thanks to their extraordinary hunting mechanism, they have inspired from a female metal band in Japan, to origami worms in Russia and video game monsters in the USA. Objective: To assess their conservation status in Costa Rica (according to data in the UNA Onychophora Database) and compare it with equivalent data from elsewhere. Methods: we located all collection records of the 29 species in the map of the Costa Rican Conservation Network. Results: We found that seven species are protected inside Forest Reserves, five in Protected Zones, four in Wildlife Refuges, two in National Parks and one, Principapillatus hitoyensis, in a strictly pristine Biological Reserve. The largest species in the world, Peripatus solorzanoi, occurs both inside a Forest Reserve and in protected private land. Protection inside Costa Rican nature areas is enforced year-round by personnel that includes armed guards and is supported by educational programs in surrounding communities. Twelve species have not been found in protected areas, but in Costa Rica, all biological species, named and unnamed, are protected by law and cannot be legally collected, or exported, without technically issued permits. Conclusion: Like in the only other country with similar information (New Zealand), the conservation of onychophorans seems to be of least concern for at least two thirds of the known Costa Rican species. Epiperipatus isthmicola, recently rediscovered after a century of absence in collections, can be considered Threatened because nearly all of its natural habitat has now been covered by a city.
UNED Research Journal.
