12 Troglocambarus maclanei Hobbs, a stygiobiont (cave dweller) (photograph courtesy of Chris Lukhaup). 

Contexts in source publication

Context 1

... (modified from Hobbs [200] ). [200] ) (cp, central projection; m, mesial process). 12a (11b). First pleopod terminating in at least three distinct elements (Fig. 22.52) 13a (12b). Dorsal surface of chela studded with crowded small tubercles ( Fig. 22.56) [200] ) (cp, central projection; m, mesial ...

Context 2

... (modified from Hobbs [200] ). [200] ) (cp, central projection; m, mesial process). 12a (11b). First pleopod terminating in at least three distinct elements (Fig. 22.52) 13a (12b). Dorsal surface of chela studded with crowded small tubercles ( Fig. 22.56) [200] ) (cp, central projection; m, mesial ...

Context 3

... (2b). Mesial surface of antennae with dense fringe of setae ( Fig. 22.8 (Fig. 22.54b, d) or, rarely, caudodistally (Fig. 22.54f) [194] ...

Context 4

... (2b). Mesial surface of antennae with dense fringe of setae ( Fig. 22.8 (Fig. 22.54b, d) or, rarely, caudodistally (Fig. 22.54f) [194] ...

Context 5

... (2b). Mesial surface of antennae with dense fringe of setae ( Fig. 22.8 (Fig. 22.54b, d) or, rarely, caudodistally (Fig. 22.54f) [194] ...

Context 6

... the glair hardens, the female is considered to be "in berry" (Fig. 22.24). As in the astacids, a positive rela- tionship exists between cambarid female size and egg number [72,349] , with large females of some epigean spe- cies carrying 600-700 eggs. More typical egg numbers for many epigean cambarid species are 25-600 [72,197,349,374] ...

Context 7

... greater diversity of reproductive and life-history pat- terns occur in cambarid crayfishes [164,169,229] . With few exceptions [390] , the cambarid life history includes alternat- ing breeding and nonbreeding morphologies for males (and females in at least some species [416] ). For many species, alter- nation between Form I (breeding) and Form II (nonbreeding) occurs at the twice yearly molt for sexually mature individu- als. In some species, for example, some Cambarellus and Procambarus, Form I males may be present year round [197] , but are generally more numerous during the fall and/or spring. Hence, many species demonstrate one or two peak periods of copulation (fall and/or spring), while in others some mating occurs throughout the year. In copulation, the male usually mounts the female [25] (Fig. 22.23). Mating gen- erally lasts from 10 min to 10 hr [9,280] . More detailed obser- vations and literature review of the reproductive morphology and mating behavior are available [7,25,203,218,242,280] ...

Context 8

... digestive system of crayfishes includes a mouth, short tubular esophagus, stomach, two large hepatopancreatic glands, short midgut, and long tubular intestine extending dorsally through the abdomen to the anus ( Fig. 22.5). The relatively straight gastrointestinal tract has few signifi- cant areas for storage or microbial degradation, although the stomach functions as a storage compartment (cardiac portion), as a masticating structure (gastric mill), and as a filter for gathering digestible material (pyloric portion). Morphological differences among species in the grind- ing surfaces of the gastric mill relate to the diet [56] . For example, the surface is reduced in some cave crayfishes that feed on organic silt, and expanded in surface dwelling (epigean) species that consume larger particles. The pH of the stomach is relatively alkaline and the enzymes of the [371] ); (B) Cambarus (Depressicambarus) strigosus Hobbs, dorsal view of telson and biramous uropod (after Hobbs [197] ); (C) Procambarus (Ortmannicus) lunzi (Hobbs), third ...

Context 9

... on the season of laying and the water tem- perature, eggs are carried by cambarid females for 2-20 weeks, during which time rhythmic movements of the pleo- pods aerate the developing eggs. After hatching, prolonged brood care involving a combination of morphological and behavioral characteristics is a unique adaptation to freshwa- ter by the Astacidea [407] . The first juvenile instar attaches to the mother with hooked chelae and a telson thread anchored by specialized hammate setae [337] . The cephalothorax of this instar is disproportionately large, with immense eyes, a yolk-laden carapace, and an incompletely developed abdo- men. Generally after two-to-seven days of attachment, juve- niles molt to a form more closely resembling the adult. This instar loses its posterior connection to the mother and uses only chelae to cling to her abdomen. An additional molt usually occurs within 4-12 days, producing a large, third- instar crayfish. Although this juvenile hangs onto the mother with its chelae and pereiopods, it may leave the parental ple- opods intermittently, and return in response to pheromones released by the mother [281] (Fig. 22.24). Subsequent instars are free-living, freeing the mother to molt, typically two- to-three weeks after all young have left. By fall, 6-10 molts have occurred in the developing juvenile, resulting in a con- siderably larger and often sexually mature adult. Many indi- viduals, however, do not become sexually active until the end of their second ...

Context 10

... circulatory system is an open or lacunar system, con- sisting of a heart, arteries (no veins), and sinuses. The heart is situated in a large mid-dorsal pericardial sinus, and blood in the sinus enters the heart via three pairs of ostia (valves) (Fig. 22.5). The nearly colorless blood is pumped into arteries that supply various organs and afferent sinuses leading to the gills, and the blood returns through a series of efferent sinuses that ultimately join to the pericardial sinus. Hemocyanin is the principal blood pigment trans- porting ...

Context 11

... (16b). Second pereiopod slender with palm three times as long as wide (Fig. 22.45b); "cascade river prawn" .. ...

Context 12

... lacking hooks on ischia of all pereiopods (Fig. 22.47a); first pleopod of male with distal portion rolled to form cylinder; male never demonstrating cyclic dimorphism; female lacking annulus ventralis . [64] ...

Context 13

... constantly diffuses into the blood through the gill surfaces, posing a physiological challenge for all fresh- water organisms. Osmotic control and excretion are main- tained by two large antennal (green) glands situated ventral to the subesophageal ganglia and anterior to the esophagus ( Fig. 22.5). These glands have an intimate association with the circulatory system and maintain water balance [134] . The green gland consists of a complexly folded end sac, a convoluted labyrinth, a nephridial canal, a bladder, and an excretory pore situated at the coxae of the second anten- nae. Crayfishes excrete a quantity of hypotonic urine (some ammonia, urea, uric acid, and amines), which is generally isosmotic with the blood [97,308,362] . High ammonia excretion rates have been correlated with low pH values (pH 4.6) [88] ...

Context 14

... gills are attached to the thoracic appendages (max- illipeds and pereiopods) and are situated along either side of the thorax in the branchial chamber. Lateral extensions of the carapace (branchiostegites) ( Fig. 22.2) cover the gills ( Fig. 22.6). In crayfishes, paddle-like second maxil- lae (scaphognathites) [54] that are anterior to the gills, beat back and forth, drawing water over the gill filaments to ensure gas exchange. The gills of caridean shrimps (phyl- lobranchs consisting of plate-like elements) and crayfishes (trichobranchs composed of unbranched, finger-like fila- ments) are arranged in three series: the single podobranchia borne on the coxa, the arthrobranchiae on the articular membrane between the coxa and the basis, and the pleuro- branchia borne on the pleura. Among North American cray- fishes, the pleurobranch series is present only in the genus Pacifastacus, which have a single pair. The penaeid shrimps have dendrobranchiate gills and those of brachyuran crabs are ...

Context 15

... gills are attached to the thoracic appendages (max- illipeds and pereiopods) and are situated along either side of the thorax in the branchial chamber. Lateral extensions of the carapace (branchiostegites) ( Fig. 22.2) cover the gills ( Fig. 22.6). In crayfishes, paddle-like second maxil- lae (scaphognathites) [54] that are anterior to the gills, beat back and forth, drawing water over the gill filaments to ensure gas exchange. The gills of caridean shrimps (phyl- lobranchs consisting of plate-like elements) and crayfishes (trichobranchs composed of unbranched, finger-like fila- ments) are arranged in three series: the single podobranchia borne on the coxa, the arthrobranchiae on the articular membrane between the coxa and the basis, and the pleuro- branchia borne on the pleura. Among North American cray- fishes, the pleurobranch series is present only in the genus Pacifastacus, which have a single pair. The penaeid shrimps have dendrobranchiate gills and those of brachyuran crabs are ...

Context 16

... crayfishes inhabiting chronically oxygen-poor habi- tats, morphological traits have evolved simultaneously with physiological changes. Many such crayfishes have a vaulted and elongated carapace as well as branchiocar- diac grooves that are closer together, thus narrowing the areola and raising the height of the chamber (Fig. 22.6). These modifications produce a greater branchial volume and increased gill surface area ( Fig. 22.7), although a great deal of variation exists around these patterns (Fig. 22.8). Other authors provide more detailed treatments of respiration, metabolism, temperature acclimation, and related topics in shrimps and crayfishes, including how these change in response to anthropogenic environmental changes [30,80,88,255,263,269,283,289,292,299,307,347] ...

Context 17

... crayfishes inhabiting chronically oxygen-poor habi- tats, morphological traits have evolved simultaneously with physiological changes. Many such crayfishes have a vaulted and elongated carapace as well as branchiocar- diac grooves that are closer together, thus narrowing the areola and raising the height of the chamber (Fig. 22.6). These modifications produce a greater branchial volume and increased gill surface area ( Fig. 22.7), although a great deal of variation exists around these patterns (Fig. 22.8). Other authors provide more detailed treatments of respiration, metabolism, temperature acclimation, and related topics in shrimps and crayfishes, including how these change in response to anthropogenic environmental changes [30,80,88,255,263,269,283,289,292,299,307,347] ...

Context 18

... crayfishes inhabiting chronically oxygen-poor habi- tats, morphological traits have evolved simultaneously with physiological changes. Many such crayfishes have a vaulted and elongated carapace as well as branchiocar- diac grooves that are closer together, thus narrowing the areola and raising the height of the chamber (Fig. 22.6). These modifications produce a greater branchial volume and increased gill surface area ( Fig. 22.7), although a great deal of variation exists around these patterns (Fig. 22.8). Other authors provide more detailed treatments of respiration, metabolism, temperature acclimation, and related topics in shrimps and crayfishes, including how these change in response to anthropogenic environmental changes [30,80,88,255,263,269,283,289,292,299,307,347] ...

Context 19

... (after Hobbs [192] ). 10a (7b). Endites of first maxilliped distinct, broad, and setose ( Fig. 22.39a) Appendix masculina with three, four, or five apical setae ( Fig. 22.40a-c) Appendix masculina with three or four apical setae ( Fig. 22.40a, b) [115] ). [379] ). Palaemonetes antrorum (after Villalobos and Hobbs [404] ). [379] ; B, after Fleming [437] ...

Context 20

... (after Hobbs [192] ). 10a (7b). Endites of first maxilliped distinct, broad, and setose ( Fig. 22.39a) Appendix masculina with three, four, or five apical setae ( Fig. 22.40a-c) Appendix masculina with three or four apical setae ( Fig. 22.40a, b) [115] ). [379] ). Palaemonetes antrorum (after Villalobos and Hobbs [404] ). [379] ; B, after Fleming [437] ...

Context 21

... (after Hobbs [192] ). 10a (7b). Endites of first maxilliped distinct, broad, and setose ( Fig. 22.39a) Appendix masculina with three, four, or five apical setae ( Fig. 22.40a-c) Appendix masculina with three or four apical setae ( Fig. 22.40a, b) [115] ). [379] ). Palaemonetes antrorum (after Villalobos and Hobbs [404] ). [379] ; B, after Fleming [437] ...

Context 22

... pair of spines on telson midway between anterior pair and posterior margin of telson ( Fig. 22.42b); appendix masculina with four apical setae ( Fig. 22.40b); "riverine grass shrimp" .. States (AL, CO, DE, FL, GA, LA, MD, MS, NC, NJ, PA, SC, TX,VA); introduced into the lower Colorado River in Arizona and California and into northern Mexico; see Fig. 22.16).] 15a (11b). Rostrum with ventral teeth (Fig. 22.43a); second pair of legs longer than first pair; appendix masculina with five apical setae, eight total setae ( Fig. 22.40c) [192] ...

Context 23

... pair of spines on telson midway between anterior pair and posterior margin of telson ( Fig. 22.42b); appendix masculina with four apical setae ( Fig. 22.40b); "riverine grass shrimp" .. States (AL, CO, DE, FL, GA, LA, MD, MS, NC, NJ, PA, SC, TX,VA); introduced into the lower Colorado River in Arizona and California and into northern Mexico; see Fig. 22.16).] 15a (11b). Rostrum with ventral teeth (Fig. 22.43a); second pair of legs longer than first pair; appendix masculina with five apical setae, eight total setae ( Fig. 22.40c) [192] ...

Context 24

... pair of spines on telson midway between anterior pair and posterior margin of telson ( Fig. 22.42b); appendix masculina with four apical setae ( Fig. 22.40b); "riverine grass shrimp" .. States (AL, CO, DE, FL, GA, LA, MD, MS, NC, NJ, PA, SC, TX,VA); introduced into the lower Colorado River in Arizona and California and into northern Mexico; see Fig. 22.16).] 15a (11b). Rostrum with ventral teeth (Fig. 22.43a); second pair of legs longer than first pair; appendix masculina with five apical setae, eight total setae ( Fig. 22.40c) [192] ...

Context 25

... pair of spines on telson midway between anterior pair and posterior margin of telson ( Fig. 22.42b); appendix masculina with four apical setae ( Fig. 22.40b); "riverine grass shrimp" .. States (AL, CO, DE, FL, GA, LA, MD, MS, NC, NJ, PA, SC, TX,VA); introduced into the lower Colorado River in Arizona and California and into northern Mexico; see Fig. 22.16).] 15a (11b). Rostrum with ventral teeth (Fig. 22.43a); second pair of legs longer than first pair; appendix masculina with five apical setae, eight total setae ( Fig. 22.40c) [192] ...

Context 26

... pair of spines on telson midway between anterior pair and posterior margin of telson ( Fig. 22.42b); appendix masculina with four apical setae ( Fig. 22.40b); "riverine grass shrimp" .. States (AL, CO, DE, FL, GA, LA, MD, MS, NC, NJ, PA, SC, TX,VA); introduced into the lower Colorado River in Arizona and California and into northern Mexico; see Fig. 22.16).] 15a (11b). Rostrum with ventral teeth (Fig. 22.43a); second pair of legs longer than first pair; appendix masculina with five apical setae, eight total setae ( Fig. 22.40c) [192] ...

Context 27

... laboratory experiments when food or shelter are limiting, crayfishes interact aggressively, with social domi- nance, size, sex, reproductive status, and body condition, all important determinants of success in agonistic encoun- ters ( Fig. 22.25). Winners of encounters are more likely to be socially dominant [279] (cf. Fero et al. [122] ), large [59,58] , male (if competing with a nonmaternal female) [127] , and with two full-size, undamaged chelae [126,257,358,397] . Competition for shelter among crayfish species is an important driver of species exclusion from some lake and stream habitats [135,180,189,316] (see Section III.C.3 for the impacts of cannibalism and ...

Context 28

... of chelae of first and second pereiopods with apical brushes of long setae ( Fig. 22.1b) Fingers of chelae of first and second perieopods without apical brushes of long setae (Fig. 22.1a) [Small coastal streams in Los Angeles and San Bernardino counties, California; probably extinct since it was last collected in 1933 [184] .] 4a (2b). Rostrum with ventral teeth and with more than 15 dorsal teeth (Fig. 22.35b) (Fig. 22.32) Rostrum elevated proximally as a spinose crest (Fig. 22.38) [438] ). [204] ...

Context 29

... of chelae of first and second pereiopods with apical brushes of long setae ( Fig. 22.1b) Fingers of chelae of first and second perieopods without apical brushes of long setae (Fig. 22.1a) [Small coastal streams in Los Angeles and San Bernardino counties, California; probably extinct since it was last collected in 1933 [184] .] 4a (2b). Rostrum with ventral teeth and with more than 15 dorsal teeth (Fig. 22.35b) (Fig. 22.32) Rostrum elevated proximally as a spinose crest (Fig. 22.38) [438] ). [204] ...

Context 30

... of chelae of first and second pereiopods with apical brushes of long setae ( Fig. 22.1b) Fingers of chelae of first and second perieopods without apical brushes of long setae (Fig. 22.1a) [Small coastal streams in Los Angeles and San Bernardino counties, California; probably extinct since it was last collected in 1933 [184] .] 4a (2b). Rostrum with ventral teeth and with more than 15 dorsal teeth (Fig. 22.35b) (Fig. 22.32) Rostrum elevated proximally as a spinose crest (Fig. 22.38) [438] ). [204] ...

Context 31

... of chelae of first and second pereiopods with apical brushes of long setae ( Fig. 22.1b) Fingers of chelae of first and second perieopods without apical brushes of long setae (Fig. 22.1a) [Small coastal streams in Los Angeles and San Bernardino counties, California; probably extinct since it was last collected in 1933 [184] .] 4a (2b). Rostrum with ventral teeth and with more than 15 dorsal teeth (Fig. 22.35b) (Fig. 22.32) Rostrum elevated proximally as a spinose crest (Fig. 22.38) [438] ). [204] ...

Context 32

... of chelae of first and second pereiopods with apical brushes of long setae ( Fig. 22.1b) Fingers of chelae of first and second perieopods without apical brushes of long setae (Fig. 22.1a) [Small coastal streams in Los Angeles and San Bernardino counties, California; probably extinct since it was last collected in 1933 [184] .] 4a (2b). Rostrum with ventral teeth and with more than 15 dorsal teeth (Fig. 22.35b) (Fig. 22.32) Rostrum elevated proximally as a spinose crest (Fig. 22.38) [438] ). [204] ...

Context 33

... a crayfish is discovered outside its shelter by a predatory fish, stereotyped antipredator behaviors occur. Depending on proximity of the predator and the shelter, a crayfish may backswim via tail-flips to its shelter, although there is a risk of capture during swimming. If escape by swimming is not possible, individuals adopt the predator- response posture, with chelae extended up and facing the predator [176] (Fig. 22.26). One selective advantage of elon- gated chelae in some species may be to sense tactilely the approach of a predator and to keep it at a greater distance. Most fishes attempt to attack a crayfish from the rear, sucking the crayfish in tail first (Fig. 22.26). When a fish is unable to approach from the rear, it may abandon the attack or end up with a crayfish clamped by its chelae onto the lower jaw of the ...

Context 34

... a crayfish is discovered outside its shelter by a predatory fish, stereotyped antipredator behaviors occur. Depending on proximity of the predator and the shelter, a crayfish may backswim via tail-flips to its shelter, although there is a risk of capture during swimming. If escape by swimming is not possible, individuals adopt the predator- response posture, with chelae extended up and facing the predator [176] (Fig. 22.26). One selective advantage of elon- gated chelae in some species may be to sense tactilely the approach of a predator and to keep it at a greater distance. Most fishes attempt to attack a crayfish from the rear, sucking the crayfish in tail first (Fig. 22.26). When a fish is unable to approach from the rear, it may abandon the attack or end up with a crayfish clamped by its chelae onto the lower jaw of the ...

Context 35

... involves far more than periods of discontinu- ous growth facilitated by a simple splitting of the cuticle and secretion of a new exoskeleton. The life of a deca- pod consists of alternating hormone-controlled periods of premolt, molt, postmolt, and intermolt. Neurosecretory cells that control endocrine function occur in two secretory masses in the eye stalk (the sensory papillae and in the X- organs of the medulla terminalis). The sinus gland, also located within the eye stalk, receives secretions from the X-organs and, in turn, produces hormones that inhibit ecdysis. The Y-organs, a pair of glands in the maxillary somites, secrete hormones derived from dietary choles- terol (three ecdysteroids: ecdysone, 25-deoxyecdysone, and 3-dehydroecdysone) that stimulate molting (under the control of the X-organ). During postmolt and intermolt, the X-organ/sinus gland complex liberates a neuropeptide molt-inhibiting hormone, thus regulating the length of the intermolt period [253] . Under appropriate external or inter- nal conditions (e.g., light, temperature, loss of limbs) [377] , sinus gland hormones are not released and the Y-organ, no longer suppressed, secretes the molt-initiating hormone. This acts on the epidermis to initiate premolt activities that affect most body parts. In preparation for molting, glycogen reserves are increased and minerals (e.g., calcium) are resorbed from the exoskeleton and stored. With the secretion of an enzyme that softens the cuticle at its base, it pulls away from the epidermal cells (apolysis), stimulating the for- mation of a new epicuticle that is impervious to the molt- ing enzyme. At the termination of premolt, the old cuticle splits at the junction of the carapace and abdomen, and the animal emerges from the old exoskeleton (now the exu- vium), including shedding the cuticle covering the gills [10] ( Fig. 22.9). As the newly molted decapod imbibes water, the soft body expands to the maximum volume, tissues grow rapidly, and the new exoskeleton becomes rigid as the stored minerals are deposited in the hardening cuticle. After postmolt, the decapod may enter intermolt. However, complete intermolt probably occurs only in adults, while rapidly growing (frequently molting) juveniles have, at best, only a very short period of intermolt stability [3,418,419] ...

Context 36

... annelids are commonly associated, and believed to be commensals, with North American crayfishes [117,222] (Fig. 22.27) (see also Chapter 12). Up to six different species have been observed on a single individual crayfish. Most of these species usually appear to be commensals, but gill damage is common when the worms are abundant on a host [117] . For crayfishes on other continents, temnocephalid turbellarian flatworms are the ecological equivalents of branchiobdellids. Unless steps are taken to prevent their introduction, they are likely to become established in North America from importation of A B live nonindigenous crayfishes (or North American species that have been housed with nonindigenous species) [117] ...

Context 37

... compressed laterally; dorsal margin of rostrum often serrate; first abdominal segment slightly smaller than others; if first and sec- ond pereiopods unequal in size, second larger or carpus of second subdivided; pereiopods often with exopods; pleopods natatory, some usually provided with appendices internae, first of male modified or not modified for sperm transfer ( Fig. 22.1 Body depressed dorsoventrally or not strongly compressed; rostrum, if distinct, always flattened dorsoventrally and often with lateral (marginal) spines; first abdominal segment always much smaller than others; first pereiopod always larger than second, carpus of second never subdivided; pereiopods lacking exopods; pleopods never natatory nor provided with appendices internae; first or first and second pleopods of male modified for sperm transfer ( Fig. 22.2) 2b. First two pairs of pereiopods usually chelate but third pair never bearing a pincer ( ...

Context 38

... compressed laterally; dorsal margin of rostrum often serrate; first abdominal segment slightly smaller than others; if first and sec- ond pereiopods unequal in size, second larger or carpus of second subdivided; pereiopods often with exopods; pleopods natatory, some usually provided with appendices internae, first of male modified or not modified for sperm transfer ( Fig. 22.1 Body depressed dorsoventrally or not strongly compressed; rostrum, if distinct, always flattened dorsoventrally and often with lateral (marginal) spines; first abdominal segment always much smaller than others; first pereiopod always larger than second, carpus of second never subdivided; pereiopods lacking exopods; pleopods never natatory nor provided with appendices internae; first or first and second pleopods of male modified for sperm transfer ( Fig. 22.2) 2b. First two pairs of pereiopods usually chelate but third pair never bearing a pincer ( ...

Context 39

... crayfishes in the family Cambaridae, molting encompasses not only growth but also reproductively important changes in morphology. Mature male cambarines alternate between reproductively competent Form I and nonbreeding Form II. Morphological differences between forms exist in male chelae size (larger in Form I), ischial spines (more pronounced in Form I), and gonopods (more sclerotized, amber-colored, and lengthened in Form I) (Fig. 22.10). At least in some Orconectes species, females also undergo form alteration, exemplified by wider abdo- mens in Form I [416,417] ...

Context 40

... encompass a tremendous diversity of colors and color pattern, between and within species. Brilliant colora- tion and striking color patterns are one of the reasons that crayfishes, in particular, are well known to aquarium hob- biests worldwide (Fig. 22.11). However, little is known of the selective value of coloration or the environmental and physiological factors that determine color or its variation in nature. Color morphs are common and especially well documented in shrimps and crayfishes, including in the shrimp Macrobrachium rosenbergii (de Man) and in the crayfishes O. propinquus, Procambarus (Ortmannicus) a. acutus (Girard) (white river crawfish), and Procambarus (Scapulicambarus) paeninsulanus (Faxon). Color varia- tions result from genetic differences [35,409] ) and environ- mental conditions [131,392] ...

Context 41

... one end of the color spectrum are obligate cave- dwelling shrimp, crayfish, and crab species, which often entirely lack pigmentation (and eyes), for evolutionary reasons that are debated but fall into three main argu- ments [39,240,338] (Fig. 22.12). First, in order to conserve energy that the construction of pigmentation (and eyes) require, it may be advantageous to lose eyes and pigmen- tation. Second, genes that are responsible for structures or pathways that are not advantageous in the dark environ- ment of caves (e.g., pigmentation, eyes) may accumulate deleterious mutations and, over generations, become non- functional. Third, genetic changes that initiate eye and pig- mentation losses might cause alterations in other structures or pathways that may be advantageous in the restricted cave environment. No matter which of the three main theories applies, the loss of pigmentation in stygobionts suggests that pigmentation and color patterns in cave-dwelling and surface-dwelling species are maintained by natural selec- tion. The tremendously varied colors and patterns suggest that color may serve important ecological functions with respect to conspecifics, similar species or predators, as it does in other colorful taxa (e.g., fishes). That bright col- oration is characteristic of many burrowing species could suggest that no strong selection exists against coloration associated with their night foraging and existence in aph- otic burrows. Such speculation about ecological and evolu- tionary importance of color begs for experimental testing. The physiological mechanisms by which color is produced are, however, well known. Chromatophores are integument cells with branched, radiating, noncontrac- tile processes that are associated with one or more types of pigment granules. White, red, yellow, blue, brown, or black pigments can flow into the processes or may be con- fined to the center of the cell. A single chromatophore may possess any number of pigments and is accordingly classi- fied as mono-, bi-, di-, or polychromatic. In shrimps, the number of pigments and the number of chromatophores can change during an individual's lifetime (Fig. 22.13). More rapid color change in shrimps, for example, to match background colors in nature, also occurs in some taxa. This results from dispersal and concentration of pigments within the chromatophores, and is controlled by hormones and the central nervous system. Chromatophorotropins are released from both the sinus gland and the central nervous system. The latter elaborates several chromatophorotro- pins, resulting in pigments either dispersing or concentrat- ing in the chromatophores. Such rapid color changes do not occur in crayfishes and freshwater ...

Context 42

... one end of the color spectrum are obligate cave- dwelling shrimp, crayfish, and crab species, which often entirely lack pigmentation (and eyes), for evolutionary reasons that are debated but fall into three main argu- ments [39,240,338] (Fig. 22.12). First, in order to conserve energy that the construction of pigmentation (and eyes) require, it may be advantageous to lose eyes and pigmen- tation. Second, genes that are responsible for structures or pathways that are not advantageous in the dark environ- ment of caves (e.g., pigmentation, eyes) may accumulate deleterious mutations and, over generations, become non- functional. Third, genetic changes that initiate eye and pig- mentation losses might cause alterations in other structures or pathways that may be advantageous in the restricted cave environment. No matter which of the three main theories applies, the loss of pigmentation in stygobionts suggests that pigmentation and color patterns in cave-dwelling and surface-dwelling species are maintained by natural selec- tion. The tremendously varied colors and patterns suggest that color may serve important ecological functions with respect to conspecifics, similar species or predators, as it does in other colorful taxa (e.g., fishes). That bright col- oration is characteristic of many burrowing species could suggest that no strong selection exists against coloration associated with their night foraging and existence in aph- otic burrows. Such speculation about ecological and evolu- tionary importance of color begs for experimental testing. The physiological mechanisms by which color is produced are, however, well known. Chromatophores are integument cells with branched, radiating, noncontrac- tile processes that are associated with one or more types of pigment granules. White, red, yellow, blue, brown, or black pigments can flow into the processes or may be con- fined to the center of the cell. A single chromatophore may possess any number of pigments and is accordingly classi- fied as mono-, bi-, di-, or polychromatic. In shrimps, the number of pigments and the number of chromatophores can change during an individual's lifetime (Fig. 22.13). More rapid color change in shrimps, for example, to match background colors in nature, also occurs in some taxa. This results from dispersal and concentration of pigments within the chromatophores, and is controlled by hormones and the central nervous system. Chromatophorotropins are released from both the sinus gland and the central nervous system. The latter elaborates several chromatophorotro- pins, resulting in pigments either dispersing or concentrat- ing in the chromatophores. Such rapid color changes do not occur in crayfishes and freshwater ...

Context 43

... decapods have the greatest diversity of all orders of crustaceans, a number of characteristics are common to all decapods. Extensive body segmentation and the presence of jointed appendages on all metameres give decapods a primitive appearance. The body of freshwa- ter decapods is encased in an exoskeleton consisting of complex polysaccharides hardened with inorganic salts (except at joints, where the cuticle is thin and pliable). The head and thoracic segments are fused to form a large cephalothorax covered by a single shield, the carapace; this applies to shrimps ( Fig. 22.1), crayfishes ( Fig. 22.2), and crabs ( Fig. 22.3). The carapace encloses the branchial (gill) chamber. The anterior portion of the cephalothorax contains a pair of large, stalked eyes, a median rostrum in shrimps and crayfishes, two pairs of antennae, and a pair of mandibles. The six abdominal segments are distinct. The cephalothorax and abdomen are composed of somites, each with a pair of ventral, jointed appendages that are serially homologous and basically biramous ( Fig. 22.4) but are modified for various functions (e.g., sensory, food handling, cleaning, gill-bailing, pinching, walking, copu- lation, egg attachment and incubation, and ...

Context 44

... decapods have the greatest diversity of all orders of crustaceans, a number of characteristics are common to all decapods. Extensive body segmentation and the presence of jointed appendages on all metameres give decapods a primitive appearance. The body of freshwa- ter decapods is encased in an exoskeleton consisting of complex polysaccharides hardened with inorganic salts (except at joints, where the cuticle is thin and pliable). The head and thoracic segments are fused to form a large cephalothorax covered by a single shield, the carapace; this applies to shrimps ( Fig. 22.1), crayfishes ( Fig. 22.2), and crabs ( Fig. 22.3). The carapace encloses the branchial (gill) chamber. The anterior portion of the cephalothorax contains a pair of large, stalked eyes, a median rostrum in shrimps and crayfishes, two pairs of antennae, and a pair of mandibles. The six abdominal segments are distinct. The cephalothorax and abdomen are composed of somites, each with a pair of ventral, jointed appendages that are serially homologous and basically biramous ( Fig. 22.4) but are modified for various functions (e.g., sensory, food handling, cleaning, gill-bailing, pinching, walking, copu- lation, egg attachment and incubation, and ...

Context 45

... decapods have the greatest diversity of all orders of crustaceans, a number of characteristics are common to all decapods. Extensive body segmentation and the presence of jointed appendages on all metameres give decapods a primitive appearance. The body of freshwa- ter decapods is encased in an exoskeleton consisting of complex polysaccharides hardened with inorganic salts (except at joints, where the cuticle is thin and pliable). The head and thoracic segments are fused to form a large cephalothorax covered by a single shield, the carapace; this applies to shrimps ( Fig. 22.1), crayfishes ( Fig. 22.2), and crabs ( Fig. 22.3). The carapace encloses the branchial (gill) chamber. The anterior portion of the cephalothorax contains a pair of large, stalked eyes, a median rostrum in shrimps and crayfishes, two pairs of antennae, and a pair of mandibles. The six abdominal segments are distinct. The cephalothorax and abdomen are composed of somites, each with a pair of ventral, jointed appendages that are serially homologous and basically biramous ( Fig. 22.4) but are modified for various functions (e.g., sensory, food handling, cleaning, gill-bailing, pinching, walking, copu- lation, egg attachment and incubation, and ...

Context 46

... decapods have the greatest diversity of all orders of crustaceans, a number of characteristics are common to all decapods. Extensive body segmentation and the presence of jointed appendages on all metameres give decapods a primitive appearance. The body of freshwa- ter decapods is encased in an exoskeleton consisting of complex polysaccharides hardened with inorganic salts (except at joints, where the cuticle is thin and pliable). The head and thoracic segments are fused to form a large cephalothorax covered by a single shield, the carapace; this applies to shrimps ( Fig. 22.1), crayfishes ( Fig. 22.2), and crabs ( Fig. 22.3). The carapace encloses the branchial (gill) chamber. The anterior portion of the cephalothorax contains a pair of large, stalked eyes, a median rostrum in shrimps and crayfishes, two pairs of antennae, and a pair of mandibles. The six abdominal segments are distinct. The cephalothorax and abdomen are composed of somites, each with a pair of ventral, jointed appendages that are serially homologous and basically biramous ( Fig. 22.4) but are modified for various functions (e.g., sensory, food handling, cleaning, gill-bailing, pinching, walking, copu- lation, egg attachment and incubation, and ...

Context 47

... typical biramous appendage is Y-shaped and the base of the "Y" is attached to the somite. The base is the pro- topodite (consisting of two joints: coxopodite and basi- opodite) which bears a mesial endopodite, typically of five podomeres, and a lateral exopodite, with few to many seg- ments ( Fig. 22.4). The first three pairs of thoracic append- ages are modified generally as maxillipeds (appendages involved in feeding and locomotion). Some features of external morphology differ among the three groups. Shrimps are generally laterally compressed relative to crayfishes and especially to crabs. Among shrimps, carideans ( Fig. 22.1) are easily distinguished (e.g., from penaeid and stenopodid shrimps) by the large second abdominal pleuron that overlaps those of both the first and third somites; moreover, all carideans lack termi- nal chelae on the third pereiopods ( Fig. ...

Context 48

... typical biramous appendage is Y-shaped and the base of the "Y" is attached to the somite. The base is the pro- topodite (consisting of two joints: coxopodite and basi- opodite) which bears a mesial endopodite, typically of five podomeres, and a lateral exopodite, with few to many seg- ments ( Fig. 22.4). The first three pairs of thoracic append- ages are modified generally as maxillipeds (appendages involved in feeding and locomotion). Some features of external morphology differ among the three groups. Shrimps are generally laterally compressed relative to crayfishes and especially to crabs. Among shrimps, carideans ( Fig. 22.1) are easily distinguished (e.g., from penaeid and stenopodid shrimps) by the large second abdominal pleuron that overlaps those of both the first and third somites; moreover, all carideans lack termi- nal chelae on the third pereiopods ( Fig. ...

Context 49

... typical biramous appendage is Y-shaped and the base of the "Y" is attached to the somite. The base is the pro- topodite (consisting of two joints: coxopodite and basi- opodite) which bears a mesial endopodite, typically of five podomeres, and a lateral exopodite, with few to many seg- ments ( Fig. 22.4). The first three pairs of thoracic append- ages are modified generally as maxillipeds (appendages involved in feeding and locomotion). Some features of external morphology differ among the three groups. Shrimps are generally laterally compressed relative to crayfishes and especially to crabs. Among shrimps, carideans ( Fig. 22.1) are easily distinguished (e.g., from penaeid and stenopodid shrimps) by the large second abdominal pleuron that overlaps those of both the first and third somites; moreover, all carideans lack termi- nal chelae on the third pereiopods ( Fig. ...

Context 50

... crayfishes of the world (and the marine lobsters) belong to the Astacidea ( Fig. 22.2), the external morphol- ogy of which is well reviewed by Holdich [440] . Features that distinguish crayfishes from anomurans (false crabs) and brachyurans (true crabs) include the following: the first three pairs of pereiopods of crayfishes are always chelate, while the second and third pereiopods of false and true crabs are not. The single false crab inhabiting North American freshwaters, Petrolisthes armatus (Gibbes) (green porcelain crab), has three pairs of well-developed pereiopods (perei- opods 2-4) with the fifth pair reduced and tucked beneath the carapace. In contrast, true crabs have four pairs of well- developed walking legs and the last or fifth pair may be modified for swimming ( Fig. ...

Context 51

... crayfishes of the world (and the marine lobsters) belong to the Astacidea ( Fig. 22.2), the external morphol- ogy of which is well reviewed by Holdich [440] . Features that distinguish crayfishes from anomurans (false crabs) and brachyurans (true crabs) include the following: the first three pairs of pereiopods of crayfishes are always chelate, while the second and third pereiopods of false and true crabs are not. The single false crab inhabiting North American freshwaters, Petrolisthes armatus (Gibbes) (green porcelain crab), has three pairs of well-developed pereiopods (perei- opods 2-4) with the fifth pair reduced and tucked beneath the carapace. In contrast, true crabs have four pairs of well- developed walking legs and the last or fifth pair may be modified for swimming ( Fig. ...

Context 52

... projection directed at angle of approximately 110° to main axis of shaft and slender mesial process at 100° angle; distal third of latter only slightly recurved distally ( Fig. 22.101a, b) Hobbseus yalobushensis Fitzpatrick and Busack (modified from Hobbs [200] ) (cp, central projection; m, mesial process). [200] ) (cp, central projection; m, mesial ...

Context 53

... ramus of uropod with distomedian spine never extending beyond posterior margin of ramus ( Fig. 22.75b); cheliped lacking suf- flamen ( [200] ) (cp, central projection; m, mesial process). [200] ) (c, cephalic process; cp, central projection; m, mesial process; s, shoulder). [200] ) (cp, central projection; m, mesial process). [200] ) (cp, central projection; m, mesial process). [206] ) (c, cephalic proc- ess; cp, central projection; m, mesial process). [200] ) (cp, central projection; m, mesial ...

Context 54

... pleopod with proximomesial spur and sometimes with cephalic process (Fig. 22.74a) Mesial ramus of uropod with distomedian spine extending beyond posterior margin of ramus ( Fig. 22.75a); cheliped with sufflamen ( Fig. 22.76a); central projection positioned proximocaudally, not overlapping that of matching pleopod (Fig. 22.77) ...

Context 55

... pleopod with proximomesial spur and sometimes with cephalic process (Fig. 22.74a) Mesial ramus of uropod with distomedian spine extending beyond posterior margin of ramus ( Fig. 22.75a); cheliped with sufflamen ( Fig. 22.76a); central projection positioned proximocaudally, not overlapping that of matching pleopod (Fig. 22.77) ...

Context 56

... pleopod with proximomesial spur and sometimes with cephalic process (Fig. 22.74a) Mesial ramus of uropod with distomedian spine extending beyond posterior margin of ramus ( Fig. 22.75a); cheliped with sufflamen ( Fig. 22.76a); central projection positioned proximocaudally, not overlapping that of matching pleopod (Fig. 22.77) ...

Context 57

... pleopod with proximomesial spur and sometimes with cephalic process (Fig. 22.74a) Mesial ramus of uropod with distomedian spine extending beyond posterior margin of ramus ( Fig. 22.75a); cheliped with sufflamen ( Fig. 22.76a); central projection positioned proximocaudally, not overlapping that of matching pleopod (Fig. 22.77) ...

Context 58

... the early 20th century, the only crayfish common in lakes of northern Wisconsin and the upper peninsula of Michigan was O. virilis (virile crayfish), but in mid-to-late 20th century, first O. propinquus (northern clearwater cray- fish) and then O. rusticus (rusty crayfish) were introduced by anglers and became widespread [318] (Fig. 22.28). Rusty crayfish, native to the Ohio River drainage in southern Indiana, northern Kentucky, and southwestern Ohio, has been widely introduced and is established in at least 17 states and Ontario (http://nas.er.usgs.gov/ARCIMS/inter- ...

Context 59

... hypotheses of decapod phylogenetic rela- tionships have been as numerous as there were authorities with points of view [364] . It is not surprising, therefore, that little consensus exists today. Traditionally, proposed rela- tionships were based on morphological studies that often produced conflicting results. Early on, the decapods were split on the basis of morphology into two groups reflecting mode of locomotion: Natantia ("swimming" lineages, e.g., shrimps) and Reptantia ("crawling" lineages, e.g., crayfishes, crabs). The Natantia then were acknowledged as a paraphyletic group and the order Decapoda was restructured into the suborders Dendrobranchiata (penaeid shrimps being the only Dendrobranchiata group treated in this chapter) and Pleocyemata (all other decapods) [55] . By combining comprehensive morphological analyses of extinct and extant forms with an array of molecular tool s [1,18,103,77,78,335,375] , the phylogenetic history of decapods is now being more clearly resolved. Nevertheless, multi- ple hypotheses remain for the relationship among lineages (Fig. ...

Context 60

... decapods occur in almost every type of surface freshwater habitat in North America, especially lakes and impoundments, ponds, marshes, swamps, rivers, streams, springs, and ditches. Glacial outwash and thermal efflu- ents are among the few freshwater habitat types not colo- nized by freshwater decapods. Many species of shrimps, crayfishes, and crabs inhabit subterranean streams and pools ( Fig. 22.14), habitats abundant in only some parts of North America (Fig. 22.15). Stygiobiont crayfishes have been observed by divers in submerged caves in north- central Florida at depths greater than 30 m. Other crayfish species live primarily in terrestrial habitats, digging bur- rows down to the water table and emerging nocturnally to forage in the terrestrial environment. In general, how- ever, many shrimp and crayfish species in North America achieve their greatest abundance in shallow, littoral areas. Shrimps, in particular, thrive in macrophyte-rich littoral zones of lakes and in sluggish, vegetation-choked streams. Many crayfishes are well adapted to both lentic and lotic habitats [324] . Geographically, decapods are most abundant in the central, eastern, and southern regions of the United States, while a few species are found in the Pacific slope drainages. Crayfishes, in particular, are rare or absent in the western Great Plains and the Rocky Mountains [388] ...

Context 61

... decapods occur in almost every type of surface freshwater habitat in North America, especially lakes and impoundments, ponds, marshes, swamps, rivers, streams, springs, and ditches. Glacial outwash and thermal efflu- ents are among the few freshwater habitat types not colo- nized by freshwater decapods. Many species of shrimps, crayfishes, and crabs inhabit subterranean streams and pools ( Fig. 22.14), habitats abundant in only some parts of North America (Fig. 22.15). Stygiobiont crayfishes have been observed by divers in submerged caves in north- central Florida at depths greater than 30 m. Other crayfish species live primarily in terrestrial habitats, digging bur- rows down to the water table and emerging nocturnally to forage in the terrestrial environment. In general, how- ever, many shrimp and crayfish species in North America achieve their greatest abundance in shallow, littoral areas. Shrimps, in particular, thrive in macrophyte-rich littoral zones of lakes and in sluggish, vegetation-choked streams. Many crayfishes are well adapted to both lentic and lotic habitats [324] . Geographically, decapods are most abundant in the central, eastern, and southern regions of the United States, while a few species are found in the Pacific slope drainages. Crayfishes, in particular, are rare or absent in the western Great Plains and the Rocky Mountains [388] ...

Context 62

... American freshwaters are inhabited by three feder- ally endangered and one probably extinct atyid species: Palaemonias ganteri, Palaemonias alabamae, Syncaris pacifica (Holmes), and Syncaris pasadenae (Kingsley), respectively [184] . The first two taxa are stygobiotic shrimps, the former restricted to Mammoth Cave in Kentucky and the latter known only from five caves (three groundwater basins) in Madison County, northeastern Alabama [235,287] (Tables 22.1, 22.2). Because most atyids currently inhabit warmer southern aquatic ecosystems, it is probable that the stygobionts are thermophilic relicts of a former, more widely distributed common ancestor. S. pacifica and S. pasadenae are found in small coastal streams of California. The former is reported from Marin, Napa, and Sonoma counties and the latter was previously reported from Los Angeles, San Bernardino, and San Diego coun- ties, but is likely extinct due to habitat destruction and over-collecting. [436] ). [19] . Seven species are inhabitants of lentic and sluggish lotic systems, including springs [379,380,428] (Fig. ...

Context 63

... genetic and fossil data, Porter et al. [335] inferred the phylogenetic relationships among the decapod sub- orders Dendrobranchiata and Pleocyemata and the infraorders within the Pleocyemata (Fig. 22.29b). Also, using Bayesian [446] and likelihood heuristic rate-smoothing methods [448] as well as fossil [442,443,445] and geological calibrations, they estimated divergence times of the order Decapoda and of its currently recognized infraorders. These studies suggest that the two suborders appeared in the early Silurian Period [437 million years ago (mya)], the informal Natantia lineages arrived as early as 417 mya with the caridean superfamilies radiating in the early Permian (263 mya). The Astacidea lineage originated 325 mya with divergence between the astacid lineages (superfamilies Astacoidea and Parastacoidea) and the Nephropoidea occurring 278 mya, which Breinholt et al. [46] refined with additional fossil evidence to about 239 mya. The split between the Astacoidea and Parastacoidea occurred 185 mya, coinciding with the break-up of Pangaea [77] . Among the Brachyuran superfamilies sampled by Porter et al. [335] , the Majoidea had the earliest lineage (254 mya), but clearly the true crabs have had a long evolutionary history that certainly predates the ...

Context 64

... surface of first pleopods with distinct shoulder near bases of terminal elements; comparatively small, thin, cephalically convex lamelliform plate directed caudodistally; mesial process broad, flattened, subtriangular, directed distolaterally; cephalic process consist- ing of small, rounded to acute knob on cephalodistal end of appendage ( Fig. 22.72 Procambarus (Remoticambarus) pecki Hobbs (modified from Hobbs [200] ) (cp, central projection; m, mesial process; s, ...

Context 65

... elements of first pleopod directed caudodistally, central projection plate-like and relatively short; mesial margin of palm of chela conspicuously longer than width of palm; carpus of cheliped only weakly expanded distally; second pereiopod lacking prominent setal fringe on merus (Fig. 22.70) Terminal elements of first pleopod directed caudally, central projection blade-like and comparatively long; mesial margin of palm of chela noticeably shorter than width of palm; carpus of cheliped expanded distally; second pereiopod with distinct setal fringe extending distally from midlength of merus distally onto dactyl (Fig. 22.71) ...

Context 66

... elements of first pleopod directed caudodistally, central projection plate-like and relatively short; mesial margin of palm of chela conspicuously longer than width of palm; carpus of cheliped only weakly expanded distally; second pereiopod lacking prominent setal fringe on merus (Fig. 22.70) Terminal elements of first pleopod directed caudally, central projection blade-like and comparatively long; mesial margin of palm of chela noticeably shorter than width of palm; carpus of cheliped expanded distally; second pereiopod with distinct setal fringe extending distally from midlength of merus distally onto dactyl (Fig. 22.71) ...

Context 67

... native and introduced species, a total of seven species assigned to the genus Macrobrachium-which is very speciose worldwide but limited in North America-are known to occur in freshwaters in the middle and lower Mississippi River drainage and in low-lying streams from New Jersey to Texas. Macrobrachium acanthurus (Wiegmann) (Cinnamon river shrimp) ranges from Georgia to Brazil (also Bahamas) and is found in the United States from Georgia and Florida to Texas along the Gulf coast. Macrobrachium carcinus (Linnaeus) (Bigclaw river shrimp) is the largest and most spectacular species and is found from Florida to Texas and south to Brazil and the West Indies (Fig. 22.17). The natu- ral range of Macrobrachium olfersii (Wiegmann) (bristled river shrimp) is from Mexico to Brazil [64] , but it has been introduced into the St. Augustine, Florida area [183] as well as Louisiana, Mississippi, and Texas. Besides M. rosenber- gii, both M. faustinum (De Saussure) and M. heterochirus (Weigman) have also naturalized in freshwater and brackish lotic environments in Florida. Macrobrachium ohione (Smith) (Ohio shrimp) is the only endemic species of the genus in North America and is found from Virginia to Texas and in the lower and middle Mississippi River drainage (Fig. ...

Context 68

... native and introduced species, a total of seven species assigned to the genus Macrobrachium-which is very speciose worldwide but limited in North America-are known to occur in freshwaters in the middle and lower Mississippi River drainage and in low-lying streams from New Jersey to Texas. Macrobrachium acanthurus (Wiegmann) (Cinnamon river shrimp) ranges from Georgia to Brazil (also Bahamas) and is found in the United States from Georgia and Florida to Texas along the Gulf coast. Macrobrachium carcinus (Linnaeus) (Bigclaw river shrimp) is the largest and most spectacular species and is found from Florida to Texas and south to Brazil and the West Indies (Fig. 22.17). The natu- ral range of Macrobrachium olfersii (Wiegmann) (bristled river shrimp) is from Mexico to Brazil [64] , but it has been introduced into the St. Augustine, Florida area [183] as well as Louisiana, Mississippi, and Texas. Besides M. rosenber- gii, both M. faustinum (De Saussure) and M. heterochirus (Weigman) have also naturalized in freshwater and brackish lotic environments in Florida. Macrobrachium ohione (Smith) (Ohio shrimp) is the only endemic species of the genus in North America and is found from Virginia to Texas and in the lower and middle Mississippi River drainage (Fig. ...

Context 69

... geographical distribution of Macrobrachium ohione. Large reductions in populations throughout its range are attribut- able to impoundments and loss of suitable habitat. Table 22.3 Classification of worldwide crayfishes, geographic distribution, and total number of described species (parentheses after generic names) (see Fig. 22.19 for distribution maps of North American genera) Pacifastacus inhabits lentic and lotic habitats ranging from alpine streams and lakes to streams crossing cold deserts. In contrast, the Cambaridae occupy a much wider diversity of habitats and comprise 417 species and subspecies (four extinct species) assigned to 12 genera distributed in east- ern Asia, Japan, and in North America east of the Rocky Mountains. In North America, cambarids occupy some Hudson Bay watersheds, the Atlantic and Gulf drainages from southern Canada through Mexico, Middle America, and Cuba ( Fig. 22.19). A total of 361 native cambarid species and subspecies are restricted to North America north of Mexico (Table 22.1) (see Hobbs [198] for lineages of the major groups in North America). Species richness for these cambarids progressively declines with increasing latituted from 30°N to 60°N (Table ...

Context 70

... three most diverse and geographically wide- spread crayfish genera are Procambarus, Cambarus, and Orconectes (Table 22.3, Fig. 22.19). The coastal plain of the southern states is dominated by Procambarus, whereas the genus Cambarus occurs primarily from the Cumberland Plateau to the north and the east ( Fig. 22.19). Species of the genus Orconectes are the most commonly encountered crayfishes to the west and northwest of the Cumberland Plateau ( Fig. 22.19). Other genera have more limited distributions. For example, the genus Cambarellus ( Fig. 22.19) is distributed below the Fall Line in the U.S. Gulf Coastal Plain. More detail on state and local distribu- tions is available from many recent sources [366,410] , includ- ing a list of publications by state [388] ...

Context 71

... three most diverse and geographically wide- spread crayfish genera are Procambarus, Cambarus, and Orconectes (Table 22.3, Fig. 22.19). The coastal plain of the southern states is dominated by Procambarus, whereas the genus Cambarus occurs primarily from the Cumberland Plateau to the north and the east ( Fig. 22.19). Species of the genus Orconectes are the most commonly encountered crayfishes to the west and northwest of the Cumberland Plateau ( Fig. 22.19). Other genera have more limited distributions. For example, the genus Cambarellus ( Fig. 22.19) is distributed below the Fall Line in the U.S. Gulf Coastal Plain. More detail on state and local distribu- tions is available from many recent sources [366,410] , includ- ing a list of publications by state [388] ...

Context 72

... three most diverse and geographically wide- spread crayfish genera are Procambarus, Cambarus, and Orconectes (Table 22.3, Fig. 22.19). The coastal plain of the southern states is dominated by Procambarus, whereas the genus Cambarus occurs primarily from the Cumberland Plateau to the north and the east ( Fig. 22.19). Species of the genus Orconectes are the most commonly encountered crayfishes to the west and northwest of the Cumberland Plateau ( Fig. 22.19). Other genera have more limited distributions. For example, the genus Cambarellus ( Fig. 22.19) is distributed below the Fall Line in the U.S. Gulf Coastal Plain. More detail on state and local distribu- tions is available from many recent sources [366,410] , includ- ing a list of publications by state [388] ...

Context 73

... three most diverse and geographically wide- spread crayfish genera are Procambarus, Cambarus, and Orconectes (Table 22.3, Fig. 22.19). The coastal plain of the southern states is dominated by Procambarus, whereas the genus Cambarus occurs primarily from the Cumberland Plateau to the north and the east ( Fig. 22.19). Species of the genus Orconectes are the most commonly encountered crayfishes to the west and northwest of the Cumberland Plateau ( Fig. 22.19). Other genera have more limited distributions. For example, the genus Cambarellus ( Fig. 22.19) is distributed below the Fall Line in the U.S. Gulf Coastal Plain. More detail on state and local distribu- tions is available from many recent sources [366,410] , includ- ing a list of publications by state [388] ...

Context 74

... projection of first pleopod tapering distally, moderately curved caudally with apex directed less than 90° to shaft of appendage; caudal process slender, situated subparallel to central projection; areola 3 times longer than wide (Fig. 22.68c, d) [200] ). [200] ...

Context 75

... elements of first pleopod always curved, never directed distally ( Fig. 22.65b, d) [200] ). [200] ). 6a (5a). Mesial process of first pleopod directed caudally at angle greater than 80° to shaft of appendage; areola 3.66 (average) times longer than wide ( Fig. 22.67d) ...

Context 76

... elements of first pleopod always curved, never directed distally ( Fig. 22.65b, d) [200] ). [200] ). 6a (5a). Mesial process of first pleopod directed caudally at angle greater than 80° to shaft of appendage; areola 3.66 (average) times longer than wide ( Fig. 22.67d) ...

Context 77

... first three genera are highly diverse, with an estimated species richness of nearly one hundred for Cambarus and Orconectes and over 140 for Procambarus. Cambarus is shown in Figs. 22.4b, 22.6a, 22.7a, c, 22.8a, 22.11d, 22.48b and 22.54. Orconectes is shown in Figs. 22.8d, 22.10, 22.11b, 22.20, 22.24a, 22.26, 22.28, 22.51, 22.53b, 22.60b, and 22.69a, b. Procambarus is shown in Figs. 22.4c, 22.6b, 22.7b, d, 22.8b, 22.9, 22.11c, g, 22.23, 22.24b, 22.25, 22.49b, and 22.52. Troglocambarus is a monotypic genus with the single species T. maclanei Hobbs, as shown in Fig. ...

Context 78

... pre-Pleistocene center of origin for the genus Orconectes probably occurred in the eastern highlands of Alabama and Tennessee which then expanded primarily to the west and north [79,123,129,131,191,193] . Some orconec- toid stock successfully moved into the lowland regions where species arose that are now assigned to the genus Faxonella. This genus also seems to have evolved on the west Gulf coastal plain and today these small, tertiary bur- rowers are found in lentic situations (ponds, ditches). They occur in flood plains and, when the water level rises, are fairly common in the shallow flowing water. Bouchardina also is derived from the orconectoid stock and occupies backwater areas. Ancestors of the members of these two genera likely arrived along the margins of the retreat- ing Mississippi embayment during the early Cenozoic. A phylogenetic representation of holarctic crayfishes sum- marizes these relationships (Fig. 22.31). Genetic studies are rapidly revealing additional surface water-dwelling species not apparent on the basis of morphological stud- ies alone [284] , and genetic patterns are clarifying phylogeo- graphic relationships [334] . Hobbs [199] ...

Context 79

... split of Pangaea into northern Laurasia and southern Gondwana landmasses resulted in the separa- tion of the ancestral crayfish lineage into the two super- families Astacoidea and Parastacoidea, respectively (see Fig. 22.30). Divergence among genera within the Parastacidae (~134 mya) occurred considerably earlier than radiation among the northern hemisphere Cambaridae (~90 mya) or the Astacidae (~76 mya) [77,335] . Whether or not the holarctic Asian Cambaroidinae and the American subfamilies shared a common freshwater ancestor or whether there were separate Asiatic and American inva- sions of freshwaters remains unclear [76,77] . Hobbs [195] sug- gested that two evolutionary lines arose from a marine nephropoid ancestral stock. One line (represented today by the genera Astacus, Austropotamobius, and Pacifastacus) moved into the freshwater habitat and maintained the primitive characteristics including the absence of cyclic dimorphism in males, and an annular sclerite lacking both a sinus and fossa in females. A second, less conserva- tive stock also made the transition to freshwaters (repre- sented by extant members of the family Cambaridae). These males evolved cyclic dimorphism and associated [77] (R  Reptantia); and (B) from Porter et al. [335] ...

Context 80

... ridges with one or two pairs of posterior spines or tubercles; rostrum lacking median carina (Fig. 22.62a) [200] ). Pacafasticus (Hobbsastacus) gambelii (Girard) (modified from Hobbs [200] ). 5a (1b). Postorbital ridges almost always spiniform cephalically, with pair of spines at posterior bases; acumen length usually greater than width of rostrum at level of marginal spines (Fig. 22.11a) Postorbital ridges rounded and smooth cephalically and with or without low tuberculiform prominences at posterior bases; acumen length rarely equal to width of rostrum at level of marginal spines (never in P. l. trowbridgii) ( Fig. 22.63) Base of postorbital ridges without tubercles (Fig. 22.63b) ...

Context 81

... ridges with one or two pairs of posterior spines or tubercles; rostrum lacking median carina (Fig. 22.62a) [200] ). Pacafasticus (Hobbsastacus) gambelii (Girard) (modified from Hobbs [200] ). 5a (1b). Postorbital ridges almost always spiniform cephalically, with pair of spines at posterior bases; acumen length usually greater than width of rostrum at level of marginal spines (Fig. 22.11a) Postorbital ridges rounded and smooth cephalically and with or without low tuberculiform prominences at posterior bases; acumen length rarely equal to width of rostrum at level of marginal spines (never in P. l. trowbridgii) ( Fig. 22.63) Base of postorbital ridges without tubercles (Fig. 22.63b) ...

Context 82

... ridges with one or two pairs of posterior spines or tubercles; rostrum lacking median carina (Fig. 22.62a) [200] ). Pacafasticus (Hobbsastacus) gambelii (Girard) (modified from Hobbs [200] ). 5a (1b). Postorbital ridges almost always spiniform cephalically, with pair of spines at posterior bases; acumen length usually greater than width of rostrum at level of marginal spines (Fig. 22.11a) Postorbital ridges rounded and smooth cephalically and with or without low tuberculiform prominences at posterior bases; acumen length rarely equal to width of rostrum at level of marginal spines (never in P. l. trowbridgii) ( Fig. 22.63) Base of postorbital ridges without tubercles (Fig. 22.63b) ...

Context 83

... ridges with one or two pairs of posterior spines or tubercles; rostrum lacking median carina (Fig. 22.62a) [200] ). Pacafasticus (Hobbsastacus) gambelii (Girard) (modified from Hobbs [200] ). 5a (1b). Postorbital ridges almost always spiniform cephalically, with pair of spines at posterior bases; acumen length usually greater than width of rostrum at level of marginal spines (Fig. 22.11a) Postorbital ridges rounded and smooth cephalically and with or without low tuberculiform prominences at posterior bases; acumen length rarely equal to width of rostrum at level of marginal spines (never in P. l. trowbridgii) ( Fig. 22.63) Base of postorbital ridges without tubercles (Fig. 22.63b) ...

Context 84

... species include burrowing and cave- dwelling crayfishes, with both habits common among cam- barids. Burrowing is probably an adaptation to minimize extremes of humidity and temperature, and as a protection against predators [15] for both adults (which can relatively easily defend the burrow) and juveniles which may live communally within them [174] . Crayfish species that are not classified as typical burrowers may occasionally construct burrows when surface waters disappear [33] or burrow into the hyporheos of streams. Burrowing crayfishes are often categorized into primary, secondary, and tertiary burrow- ers [197] (Fig. 22.21), as described below. Other authors pro- vide additional details about burrowing behavior [163,352] , including a more comprehensive categorization for bur- rowing crayfishes [413] ...

Context 85

... serrate (at least three pairs of marginal spines; Fig. 22.59a, b); abdominal pleura acute; incisor region of mandible blade-like ( Fig. 22.60a) [200] ). saxatilis Bouchard and Bouchard Girard (after Bouchard [40] ...

Context 86

... serrate (at least three pairs of marginal spines; Fig. 22.59a, b); abdominal pleura acute; incisor region of mandible blade-like ( Fig. 22.60a) [200] ). saxatilis Bouchard and Bouchard Girard (after Bouchard [40] ...

Context 87

... the cambarids, a wide range of habitats and habits exist. A common daytime habit among stream and lake-dwelling crayfishes is the occupation of inter- stices (e.g., among stones, weed beds, leaf litter, brush piles, logjams, roots of riparian trees) that afford protec- tion from predation by fishes, birds, and other crayfishes (particularly during molting) [5,316] (Fig. 22.20). In streams, interstices also protect crayfishes from being swept away in floods [316] . Astacids and epigean species of cambarids are typically very strongly associated with interstices, especially with cobble habitats, which provide the most available habitat structure in many streams and lakes [263] . Lakewide population density of Orconectes spp, for exam- ple, is positively associated with the percentage of the lit- toral zone occupied by cobble substrate [263] , suggesting that habitat often may limit the size of crayfish popula- tions. However, crayfish abundance is not high in all lakes with abundant habitat, implying that other factors, prob- ably including food and predators, may sometimes limit populations also (see Section ...

Context 88

... burrowers (e.g., Procambarus a. acutus) live in open waters and move into burrows only at specific periods to brood eggs, to move below the frost line during winter, and to avoid dessication ( Fig. ...

Context 89

... burrowers spend most of their lives in bur- rows, occasionally exiting to forage or to mate. These crayfish dig their burrows, often forming the excavated soil into aboveground chimneys ( Fig. 22.22); the burrows consist of complex tunnels which for some species are typ- ically in seepage areas, along stream banks, in open fields, and in other low-lying areas ( Fig. 22.21). The burrows of other species are often quite removed from open bod- ies of water, with some species most common in upland habitats [414] . Other primary burrowers [e.g., Fallicambarus (Creaserinus) gordoni Fitzpatrick] are found only in pitcher-plant bogs [240] . Primary burrowers exist in the genera Cambarus, Distocambarus, Fallicambarus, and Procambarus. Primary burrowers emerge from burrows under low light, apparently for foraging and mating, while high light levels cause withdrawal, apparently an antipreda- tor behavior [121] . In general, however, the behavior and [199] ...

Context 90

... burrowers spend most of their lives in bur- rows, occasionally exiting to forage or to mate. These crayfish dig their burrows, often forming the excavated soil into aboveground chimneys ( Fig. 22.22); the burrows consist of complex tunnels which for some species are typ- ically in seepage areas, along stream banks, in open fields, and in other low-lying areas ( Fig. 22.21). The burrows of other species are often quite removed from open bod- ies of water, with some species most common in upland habitats [414] . Other primary burrowers [e.g., Fallicambarus (Creaserinus) gordoni Fitzpatrick] are found only in pitcher-plant bogs [240] . Primary burrowers exist in the genera Cambarus, Distocambarus, Fallicambarus, and Procambarus. Primary burrowers emerge from burrows under low light, apparently for foraging and mating, while high light levels cause withdrawal, apparently an antipreda- tor behavior [121] . In general, however, the behavior and [199] ...

Context 91

... different set of morphological characteristics occurs in primary burrowing crayfishes. They have an enlarged gill chamber (discussed earlier) and short, broad, flattened chelipeds for digging; they also lack carapace spines and have a reduced abdomen and tail fan (length, width, and height) [76] (Fig. 22.8). Many primary burrowing species also are brightly infused with blue, red, green, and gold pigments of uncertain adaptive significance in the low light environments these crayfish inhabit ( Fig. 22.11); indeed, this may indicate the absence of strong selection against bright pigments in the dark environment of burrows. In con- trast, species dwelling in fast-flowing water have depressed (dorsoventrally flattened-most common) or compressed (laterally deflated) bodies, for example, Orconectes (Gremicambarus) compressus (Faxon) ("slender crayfish") and Procambarus (Tenuicambarus) tenuis Hobbs. Spination is also typically reduced in such species. Species inhabiting pebble and cobble habitats in stream riffles are depressed dorsoventrally, for example, Cambarus (Jugicambarus) friaufi Hobbs ("hairy crayfish") and Cambarus (J.) brach- ydactylus Hobbs. Many stream-dwelling species also have large abdomens for swimming [76] , and alter their posture in response to high flow to counteract the effects of drag [285] ...

Context 92

... different set of morphological characteristics occurs in primary burrowing crayfishes. They have an enlarged gill chamber (discussed earlier) and short, broad, flattened chelipeds for digging; they also lack carapace spines and have a reduced abdomen and tail fan (length, width, and height) [76] (Fig. 22.8). Many primary burrowing species also are brightly infused with blue, red, green, and gold pigments of uncertain adaptive significance in the low light environments these crayfish inhabit ( Fig. 22.11); indeed, this may indicate the absence of strong selection against bright pigments in the dark environment of burrows. In con- trast, species dwelling in fast-flowing water have depressed (dorsoventrally flattened-most common) or compressed (laterally deflated) bodies, for example, Orconectes (Gremicambarus) compressus (Faxon) ("slender crayfish") and Procambarus (Tenuicambarus) tenuis Hobbs. Spination is also typically reduced in such species. Species inhabiting pebble and cobble habitats in stream riffles are depressed dorsoventrally, for example, Cambarus (Jugicambarus) friaufi Hobbs ("hairy crayfish") and Cambarus (J.) brach- ydactylus Hobbs. Many stream-dwelling species also have large abdomens for swimming [76] , and alter their posture in response to high flow to counteract the effects of drag [285] ...

Context 93

... and Payne (after Hobbs [200] ). [200] , in part) (cp, central projection; m, mesial process; s, proximomesial spur). 15a (14b). Carpus of cheliped slender and longer than mesial margin of palm of chela ( Fig. 22.58c); rostrum without marginal spines (Fig. 22.58a ...

Context 94

... and Payne (after Hobbs [200] ). [200] , in part) (cp, central projection; m, mesial process; s, proximomesial spur). 15a (14b). Carpus of cheliped slender and longer than mesial margin of palm of chela ( Fig. 22.58c); rostrum without marginal spines (Fig. 22.58a ...

Context 95

... crayfish taxa occupying similar habitats have converged morphologically [53,196] . For example, stygobiotic shrimps, crayfishes, and crabs around the world exhibit classic convergent adaptations for living in stygian envi- ronments and are characterized by loss of pigmentation and [197] , p. 32; see also Hobbs and Whiteman [207] , Fig. 2). eyes, elongated antennae, elongated and attenuated append- ages, long life (some well beyond 20 yr), and extreme resource efficiency in the energy-poor cave environment [76] ( Fig. 22.12). In at least three genera of stygobionts, vestig- ial eyes have become tactile and/or chemosensory recep- tors, complete with setae on the corneal surface [293] ...