Crab Body Research Articles

Skeletal muscle fiber types in the ghost crab,Ocypode quadrata:implications for running performance

Ghost crabs possess rapid running capabilities, which make them good candidates for comparing invertebrate exercise physiology with that of more extensively studied vertebrates. While a number of studies have examined various aspects of running physiology and biomechanics in terrestrial crabs, none to date have defined the basic skeletal muscle fiber types that power locomotion. In the current study, we investigated skeletal muscle fiber types comprising the extensor and flexor carpopodite muscles in relation to running performance in the ghost crab. We used kinematic analyses to determine stride frequency and muscle shortening velocity and found that both parameters are similar to those of comparably sized mammals but slower than those observed in running lizards. Using several complementary methods, we found that the muscles are divided into two primary fiber types: those of the proximal and distal regions possess long sarcomeres (6.2+/-2.3 microm) observed in crustacean slow fibers and have characteristics of aerobic fibers whereas those of the muscle mid-region have short sarcomeres (3.5+/-0.4 microm) characteristic of fast fibers and appear to be glycolytic. Each fiber type is characterized by several different myofibrillar protein isoforms including multiple isoforms of myosin heavy chain (MHC), troponin I (TnI), troponin T (TnT) and a crustacean fast muscle protein, P75. Three different isoforms of MHC are differentially expressed in the muscles, with fibers of the mid-region always co-expressing two isoforms at a 1:1 ratio within single fibers. Based on our analyses, we propose that these muscles are functionally divided into a two-geared system, with the aerobic fibers used for slow sustained activities and the glycolytic mid-region fibers being reserved for explosive sprints. Finally, we identified subtle differences in myofibrillar isoform expression correlated with crab body size, which changes by several orders of magnitude during an animal's lifetime.

Effects of epibioticEnteromorphaspp. on the mole crabEmerita analogain the Peruvian central coast

Epibiotic interactions between macroalgae and crustaceans have rarely been described. We examined the interaction between the mole crab,Emerita analogaand the opportunistic algaeEnteromophaspp. in a sandy beach of the central coast of Peru.Enteromorphaspp. was found fouling the carapace of the mole crab that provides the only stable substrate to spore settlement in the beach environment. Epibiosis prevalence was up to 2.1%, and affected mainly larger, ovigerous females. Prevalence presented a seasonal pattern, with peaks during summer. Mole crab body condition was higher when fouled, whereas fecundity was not affected. Fouled mole crabs burrowed at lower speed, which was reversible by the removal of epibiotic algae. The burrowing depth was not affected by epibiosis. Contrary to the expected, the effects of algal epibiosis on demographic and life history parameters of mole crabs, with the exception of body condition, were mainly neutral but important on behavioural traits.

Comparison of fatty acid and proximate compositions of the body and claw of male and female blue crabs (Callinectes sapidus) from different regions of the Mediterranean coast

Fatty acid and proximate compositions of the body and claw of male and female blue crabs from Akyatan Lagoon and Hurma strait were investigated. Male blue crab meat had a higher protein and fat content, and lower moisture and ash content, than that of the female from Akyatan Lagoon. Moreover, there were variations of protein and fat amounts in both female crab meats between Akyatan Lagoon and Hurma strait. The dominant saturated fatty acids were palmitic acid (16:0; range from ∼12% to 15%) and stearic acid (18:0; range from ∼7.5% to 16.1%) for all samples. The total monounsaturated fatty acid content in the body of female crabs from Akyatan Lagoon was higher than those of Hurma Strait (22.04% versus 7.55%). There were no statistically significant differences (P >0.05) between eicosapentaenoic acid concentrations in body meat of the male crab than those of female crab meat from Akyatan Lagoon (P<0.05). Docosahexaenoic acid contents were different between the body meat of male crabs from Akyatan Lagoon and those of female crabs from Hurma strait. The total n3 was detected as 27.33% in body meat whereas it was 24.39% in claw meat of the male crab from Akyatan Lagoon. Those values were almost similar in the body and claw meat of female crab from Akyatan Lagoon.

Finding of Pebrilla paguri (Ciliata, Folliculinidae, Heterotricha) epibiont inside the shells of two hermit crab species, Calcinus tubularis and Clibanarius erythropus (Decapoda, Anomura, Diogenidae)

Ever since its discovery, Pebrilla paguri was considered to be an exclusive epibiont of hermit crabs. In fact, up to now, it has never been recorded on substrata other than the hermit crab exoskeleton. The finding of its loricae on non‐consecutive exuviae, released by the same specimen of Calcinus tubularis, suggested that the motile stage may transform into the sessile form and attach itself to the shell occupied by the crab. All the shells occupied by the C. tubularis and Clibanarius erythropus specimens showing the ciliate on the exoskeleton were identified to genus level; for each shell genus a map of the inner morphology was drawn in order to record the position and number of the loricae. The present research showed that P. paguri is not an exclusive hermit crab epibiont: it also attaches itself to shells, and particularly to the three largest whorls, corresponding to the portion occupied by the crab body. The presence of P. paguri in the shell may be determined by the preference for substrata characterized by a particular water stream or light levels. The results obtained show that the P. paguri substrata choice is more similar to that of other folliculinids, and more varied than previously reported.

Incremental ecological exposure risks from contaminated sediments in an urban estuarine river

Estuaries in urban regions present unique environmental management challenges. Ecosystems in urban estuaries are typically impacted by habitat loss and degradation, watershed modification, and nonpoint and point sources of many chemicals. Restoring such systems requires an understanding of the relative contribution of various stressors to overall ecological conditions and an understanding of shifting patterns of stress over time. In this article, we present the results of a multiparameter environmental assessment of a quintessential urbanized waterway: the lower Passaic River in the vicinity of Newark, New Jersey, USA. To provide the foundation for effective management decision making, we quantified baseline conditions (habitat losses and degradation), chemical concentrations in sediment and biota relative to published toxic effect levels, direct toxicity of sediments to benthic organisms, and food-web mediated risks to fish-eating birds. Habitat losses have been severe (greater than 85% of wetlands, nearly 100% of the total length of tidal and nontidal tributaries, and 100% of natural shoreline habitat have been lost), resulting in substantial habitat constraints on biota. Despite this, biological communities are present in the lower Passaic. In general, concentrations of toxic chemicals in surface sediments have fallen with time, and natural recovery processes are proceeding. Chemical concentrations remain high enough to impair survival of amphipods, but not amphipod growth or polychaete growth or survival as measured in laboratory bioassays using field-collected sediment. Fish and blue crab body burdens of some metals, PCBs, and the pesticide, DDT, are at concentrations sufficiently high to exceed toxicity thresholds. The resident fish-eating bird--the belted kingfisher--is at exposure risk from some metals, PCBs, and polychlorinated dibenzo-p-dioxins and dibenzo furans (PCDD/Fs). Migratory waders--the herons and egrets--are not at risk from chemical exposure. These complex findings suggest that restoring the lower Passaic River to ecological health is a correspondingly complex task. Habitat constraints must be eased for biotic components of the ecosystem, and chemical effects must be reduced for those organisms that are present. Only a coordinated, multidisciplinary restoration program will succeed in this challenging environment.

HCHs and DDTs in sediment-dwelling animals from the Yangtze Estuary, China

HCHs and DDTs in sediment-dwelling animals including mollusks and crabs from the Yangtze Estuary were determined by GC-ECD. Levels of t-HCH were in the range of 1.2–5.5 ng g −1 and averaged 3.5 ng g −1 in mollusks, while t-DDT concentrations ranged from 26.0 to 68.8 ng g −1, with a mean of 34.5 ng g −1. In crabs t-HCH concentrations varied from 2.0 to 25.7 ng g −1 and averaged 13.8 ng g −1, whereas the concentrations of t-DDT were in the range of 1.5–24.8 ng g −1 with a mean value of 5.9 ng g −1. The HCHs and DDTs levels depend on geographical position and sources, showing the high levels at fresh water area in the estuary, such as XP, CM and LHK sites, and lower at brackish water area, such as FX site, and little difference between species. Results also indicate there was no significant relationship between t-HCH ( t-DDT) concentrations and lipid contents both in mollusks and crabs because of non-equilibrium state under a specific estuarine dynamics; smaller individuals accumulated more HCHs and DDTs than larger individuals of mollusks at LHK site, showing different uptake rate for these pesticides; moreover, HCHs and DDTs levels were lower in female crab bodies than male crab bodies suggesting that the release of spawning. BSAFs (Biota- Sediment Accumulation Factors) from sediment-dwelling animals for HCHs and DDTs show a significant “one high with two low” and “one low with two high” effect in the Yangtze Estuary.

New morphometric parameters for assessment of body size in the fossil freshwater crab assemblage from the Acheulian site of Gesher Benot Ya'aqov, Israel

The faunal assemblage of Gesher Benot Ya'aqov (GBY) in the northern Jordan Valley, Israel, a waterlogged Early–Middle Pleistocene Acheulian site (0.79 Ma) correlated with Oxygen Isotope Stage (OIS) 20.2–18.2, includes over 5000 fragments (1–40 mm) of fossil freshwater crab of an undetermined species suspected to be Potamon sp., based on the morphology of its pincers. Most of the fragments (92.6%) were identified to crab body part, of which 74.6% are pincers. The fossil crabs of GBY demonstrate four distinct pincers, as is also typical of the present-day species in the region, Potamon potamios. In this study we propose for the first time a series of 22 easily measurable morphometric parameters that permit assessment of the pincer size of fossil freshwater crabs from measurable fragmented pincers (35.5% of fragments). We assume that the pincer length represents the crab body size, as in the recent species in the region. The study was restricted to GBY Area C layer V-6, which yielded 91.6% of the crab fragments found in Area C. It has been found that the measurable parameters are significantly correlated to the length of the related pincer ( r = 0.671 – 0.955 , P < 0.0025 ). The same parameters measured for comparison in 208 specimens of recent Potamon potamios, mainly from the same region, resulted in higher correlations ( r = 0.806 – 0.990 , P < 0.0002 ). Consequently, even if fossil crab remains are very fragmentary, it is still possible to reconstruct the body size of the crab. Regression line equations are given as an implicative tool for future assessment of the pincer size of fragmentary fossil crabs from the region. The GBY pincer length data indicate that the broad size range seen in living populations of Potamon potamios also exists in the GBY fossil crabs. A minimum number of individuals (MNI) resulted in a very high density of 668 specimens (321 specimens per m 3). In cluster analyses for each of the 22 parameters, the mean of the GBY crab population measurements is consistently smaller than that of the recent crabs, in which females display intermediate values and males are the largest. However, when allometry is also taken into consideration, cluster analysis groups together the recent males and the recent females and distinctly separates them from the GBY crabs. Further allometric analyses of fossil crab populations from earlier and later prehistoric sites in the northern Jordan Valley will enable a better understanding of the significance of these differences and possible evolutionary trends in the fossil crab population's taxonomy.

Incremental Ecological Exposure Risks from Contaminated Sediments in an Urban Estuarine River

Estuaries in urban regions present unique environmental management challenges. Ecosystems in urban estuaries are typically impacted by habitat loss and degradation, watershed modification, and nonpoint and point sources of many chemicals. Restoring such systems requires an understanding of the relative contribution of various stressors to overall ecological conditions and an understanding of shifting patterns of stress over time. In this article, we present the results of a multiparameter environmental assessment of a quintessential urbanized waterway: the lower Passaic River in the vicinity of Newark, New Jersey, USA. To provide the foundation for effective management decision making, we quantified baseline conditions (habitat losses and degradation), chemical concentrations in sediment and biota relative to published toxic effect levels, direct toxicity of sediments to benthic organisms, and food-web mediated risks to fish-eating birds. Habitat losses have been severe (greater than 85% of wetlands, nearly 100% of the total length of tidal and nontidal tributaries, and 100% of natural shoreline habitat have been lost), resulting in substantial habitat constraints on biota. Despite this, biological communities are present in the lower Passaic. In general, concentrations of toxic chemicals in surface sediments have fallen with time, and natural recovery processes are proceeding. Chemical concentrations remain high enough to impair survival of amphipods, but not amphipod growth or polychaete growth or survival as measured in laboratory bioassays using field-collected sediment. Fish and blue crab body burdens of some metals, PCBs, and the pesticide, DDT, are at concentrations sufficiently high to exceed toxicity thresholds. The resident fish-eating bird—the belted kingfisher—is at exposure risk from some metals, PCBs, and polychlorinated dibenzo-p-dioxins and dibenzo furans (PCDD/Fs). Migratory waders—the herons and egrets—are not at risk from chemical exposure. These complex findings suggest that restoring the lower Passaic River to ecological health is a correspondingly complex task. Habitat constraints must be eased for biotic components of the ecosystem, and chemical effects must be reduced for those organisms that are present. Only a coordinated, multidisciplinary restoration program will succeed in this challenging environment.

Body and resource size at the land?sea interface

Body size in animals varies with many parameters, amongst them taxonomic affiliation, lifestyle and ambient environment oxygen levels. Size has considerable implication to possibilities for animals; for example, parasites need to be small and top predators large. Body size and resource requirements (shell size) were investigated across the land–sea interface in hermit crabs (Crustacea: Malacostraca: Decapoda) and snails (Mollusca: Gastropoda: Prosobranchia). These are two of the few taxa to occur in the sea, on the shore and on land as residents. Both taxa are also appropriate for such an analysis as they are abundant, speciose, cohabit the same environments and are linked—gastropod shells are a critical resource to hermit crabs. Both the maximum and mean sizes of hermit crab species showed parabolic relationships with shore height, decreasing from the sublittoral and supralittoral to the eulittoral. Average maximum size of gastropods exhibited a similar intertidal minimum although variability was high. It is suggested that this pattern is robust: not only did two distantly related taxa show the same pattern, but neither region nor site contributed significantly to total variability. The mass of resources (gastropod shells) used by hermit crabs, however, showed a converse pattern. The smallest shells (relative to hermit crab body size) were used in the sublittoral and supralittoral. Response to environmental stress and predation pressure are offered as two alternate theories to explain the observed body dwarfism and resource gigantism in the intertidal zone.

Late-Holocene Dungeness crab (Cancer magister) harvest at an Oregon coast estuary

Coastal peoples worldwide harvested and consumed a wide variety of shellfish. Most archaeological analyses of shellfish remains tend to focus on bivalves such as clams and mussels while other shellfish such as gastropods, barnacles, and crabs have received much less attention. Here we examine the use of Dungeness crabs ( Cancer magister ) at a late-Holocene village on Netarts Bay, northern Oregon Coast. Ethnographic and ethnohistoric records suggest that crabs were both individually hunted as well as gathered, often en masse. We employ allometric scaling of Dungeness claws (propal fingers) recovered from several household middens to estimate crab body size and age. These data indicate that while a wide age range of crabs were collected, most harvesting efforts focused on juveniles and young adults. This suggests that most Dungeness crabs at the site were gathered (not individually hunted) in Netarts Bay, most likely in shallow subtidal areas where cockles ( Clinocardium nuttalli ) were also being regularly taken. As such, Dungeness crabs were part of a foraging strategy that involved the efficient mass harvest of small prey using minimal technology.

Pebrilla paguri (Ciliophora, Folliculinidae) on four Mediterranean hermit crab species

The present research aims at broadening the range of possible Pebrilla paguri hosts, by analysing various Mediterranean hermit crab species, as well as at investigating their preferential distribution on the crustacean body. For each crab carrying P. paguri on its exoskeleton, the position and number of the ciliate's loricae were recorded and mapped. Pebrilla paguri loricae were observed only on 16.6% of the hermit crabs examined, with a greater number being observed on Calcinus tubularis and Paguristes eremita, compared to the two other crab species. A reason for this may be that the former are not very active in feeding, motion, and interaction. The highest frequency of P. paguri was observed on the abdomen, telson, and uropods, whereas only a few were found on the cephalotorax. This localisation is discussed in relation to the epibiont's preference for parts of the crab's body that are normally kept deep inside the molluscan shell and characterised by scarce water flow and illumination. These conditions will promote bacterial proliferation and accumulation of the organic residuals, which will become available for P. paguri as food. The preferential distribution of ciliates on the left side of the crab's body can be seen as a way to avoid damage by rubbing against the shell's columella.

Lead burdens and behavioral impairments of the lined shore crab Pachygrapsus crassipes.

Sublethal burdens of lead impair behaviors critical to survival in a variety of animals. In a test arena, I measured refuge-seeking behaviors of adult, male, lined shore crabs from lead-free and lead-contaminated sites. The body sizes of the test groups did not differ although the mean total body lead burdens differed by over 2,300%. A lead-contaminated environment does not appear to affect growth. Each of the 31 crabs had at least six trials in the arena. The fraction of trials with more than one pause, number of pauses per trial, mean time per pause, and the fraction of time a crab spent in pauses did not differ between groups. The absence of behavioral effects of the lead burdens may be because a large portion of the lead burden was sequestered in the carapace. The neurological and other soft tissues would then have lower levels of lead. Predators that ingest primarily soft tissues would have little exposure to the lead burden of these crabs. Those that also ingest the carapace may benefit from its high calcium content that inhibits lead uptake from the gut, regardless of the location of lead in the crab body.

Effects of the Stocking Density and Body Size of the Mitten Crab (Eriocheir sinensis) on Aquatic Plant Biomass

ABSTRACT Experiments in tanks and cages were conducted to examine the effects of stocking density and body size of the mitten crab (Eriocheir sinensis) on transplanted submersed macrophyte biomass. The early juvenile crab with 7.0±0.6 mm carapace width (CW) had little effect on plant biomass, regardless of the stocking densities. However, larger crabs (CW: 18.0±2.2, 35.0±3.6, and 60.0±5.7 mm) significantly influenced plant biomass, especially at large stocking densities. Predictive models, using crab body size and stocking density, were generated to demonstrate effect of the mitten crab on the changes of plant biomass. The results indicate that dense mitten crab populations may adversely affect aquatic plant communities, particularly when its animal food resources are scarce.

Release from Parasites as Natural Enemies: Increased Performance of a Globally Introduced Marine Crab

Introduced species often seem to perform better than conspecifics in their native range. This is apparent in the high densities they may achieve or the larger individual sizes they attain. A prominent hypothesis explaining the success of introduced terrestrial species is that they are typically free of or are less affected by the natural enemies (competitors, predators, and parasites) they encounter in their introduced range compared to their native range. To test this hypothesis in a marine system, we conducted a global assessment of the effect of parasitism and predation on the ecological performance of European green crab populations. In Europe, where the green crab is native, crab body size and biomass were negatively associated with the prevalence of parasitic castrators. When we compared native crab populations with those from introduced regions, limb loss (an estimator of predation) was not significantly lower in introduced regions, parasites infected introduced populations substantially less and crabs in introduced regions were larger and exhibited a greater biomass. Our results are consistent with the general prediction that introduced species suffer less from parasites compared to populations where they are native. This may partly explain why the green crab is such a successful invader and, subsequently, why it is a pest in so many places.

Aspects of evolution in the anomuran superfamily Paguroidea: one larval prospective

Summary McLaughlin and Lemaitre (1997), in their examination of carcinization in the Anomura, rejected the traditional concept of paguroid evolution, which had consistently maintained that the lithodid crab-like body form evolved from a typical shell-dwelling hermit crab. Their hypothesis proposed just the reverse, i.e., the lithodid crab-like body form gave rise to the simple hermit crab body form through calcium loss, habitat change and consequential morphological adaptations. Their original hypothesis was based on characters derived from adult morphology, but they suggested that larval data would support their view. The megalopal and first or first- and second-crab stages of representatives of both subfamilies of the Lithodidae provide the first of such larval information. Ten species in eight genera have been examined specifically for development of abdominal tergites. These data, although preliminary in scope, unequivocally disprove the Bouvierian concept of lithodid abdominal plate development, and in so doing, lend substantial support to McLaughlin and Lemaitre's hypothesis.

Cannibalism in the snow crab, Chionoecetes opilio (O. Fabricius) (Brachyura: Majidae), and its potential importance to recruitment

Density-dependent cannibalism, either on early benthic instars or on late prerecruits, has been hypothesized to regulate recruitment in the snow crab Chionoecetes opilio (O. Fabricius). However, there is little direct empirical or experimental evidence to support these hypotheses. We examined the stomach contents of 1218 C. opilio of 12–135 mm carapace width (CW) for evidence of cannibalism. Crabs were collected by beam trawl in 1993 and 1994 in the estuary and northwest gulf of the Saint Lawrence River (Canada). Complementary laboratory experiments served to constitute a library of digested crab body parts for reference in the identification of stomach contents, and to evaluate the possibility and size-specificity of cannibalism on C. opilio instar I (settlers: 3 mm CW). The natural diet of C. opilio changed with increasing body size, with smallest crabs feeding mainly on amphipods and ophiuroids, while the largest crabs fed mainly on annelids, crustacean decapods and fish. Overall, conspecifics other than exuviae occurred in the stomachs of 7.2% of wild caught C. opilio and were probably derived through predation rather than scavenged. Non-exuvial conspecifics were found most frequently in the stomachs of adult males (sperm-producing, chelae differentiated), with occurrence declining significantly from 22% to 6% of adult males by 10 mm CW size class over the range of 50–120 mm CW. Conspecific prey ranged in size from 3.9–48.8 mm CW, but most were immature crabs belonging to molt instars V (≈ 15 mm CW), VI (≈ 20 mm CW) and VII (≈ 28 mm CW). In the laboratory, instar I crabs were cannibalized by males of 8–50 mm CW, but not by males of 51–130 mm CW. Based on laboratory and field results, there are relative lower and upper size thresholds for vulnerability of intermolt crabs to cannibalism, which vary with predator size. We conclude that intraspecific predation may reduce cohort strength mainly over the first 4 years following settlement.

Distribution of Ciliate Epibionts on the Portunid Crab Liocarcinus depurator (Decapoda: Brachyura)

Epibiont ciliates on the exoskeleton of the decapod crustacean Liocarcinus depurator, a portunid crab collected off the Mediterranean coast of Spain, included 11 species, belonging to three subclasses. The chonotrich Chilodochona quennerstedti, the most abundant species, colonized specific sites on the crab, the mouthparts. The peritrichs, identified as Zoothamnium sp. and Cothurnia sp., and the suctorians, identified as Acineta tuberosa, Acineta papillifera, Ephelota gemmipara, Actinocyathula homari, Paracineta limbata, Conchacineta constricta, Corynophrya anisostyla, and Acinetides symbiotica, were generally less site-specific. Feeding activities, burying behavior, and molt state of the host crab, and competition between ciliate species, are mentioned as the most important factors in the occurrence of ciliates on the crustacean body. Additional key words: epibiosis, Chonotrichia, Peritrichia, Suctoria, burying crab Decapod crustaceans are frequently hosts, or basibionts, of diverse sessile invertebrate metazoans (hydrozoans, bryozoans, cirripeds, polychaetes, etc.) although, to some extent, the molt of crustaceans, especially young, fast-growing individuals, keeps the exoskeleton free of epibionts (Ross 1983). Protozoans constitute another group of epibionts, probably less well known (see annotated list of parasite and ectocommensal protists of decapod crustaceans, Sprague & Couch 1971). Several subsequent studies on parasitic protozoans and diseases caused in some peneid decapods of economic importance (Overstreet 1987) have noted mainly the pathological effects of the presence of epibionts. Also, many ciliate species-apostomatids, peritrichs, suctorians, heterotrichs, and chonotrichs-have been reported as present on crustaceans (Collin 1912; Fenchel 1965; Corliss 1979; Batisse 1986, 1992; Clamp 1991). However, most of these studies have focused on describing the morphological features of the protozoans; in few cases have the ecology and the relationships with the host been considered. Many sessile marine organisms depend on the physical characteristics of the substrate to which they are attached (Gili et al. 1993); hence, the structure and dynamics of the substrate is reflected in the pattern of colonization by epibiont species. In the same way, epibiosis can contribute to the description and explanation of important aspects of the biology and ecology of basibiont crustacean species (Bottom & Ropes 1988; Abello et al. 1990; Abello & Macpherson 1992; Gili et al. 1993). Molt cycles and reproductive behavior are some of features studied using macroepibionts and their distribution patterns. However, this type of study does not take into account the epibiont protozoan communities. Liocarcinus depurator LINNAEUS 1758 is a portunid crab living in muddy beds of the continental shelf, at depths between 1 and 100 m (Abello 1986). During the period between the molts, these crabs are an available substrate for epibionts. We have described the ciliate groups most commonly found on the exoskeleton of L. depurator and their distribution on the crab's body. The settlement and development of these protozoan communities is determined not only by environmental conditions, but also by the biology and behavior of the crustacean.

Orchomene nanus (Krøyer) (Amphipoda: Lysianassoidea), a selective scavenger of dead crabs: feeding preferences in the field

Simultaneously deployed multiple-trap rigs were proven to function replicably at a shallow-water (5–6 m) study site. A standard (crushed) bait of whole crabs [ Carcinus maenas (L.)] attracted significantly more Orchomene nanus than control (unbaited) traps. Traps were not inherently attractive. Crab bait was significantly more attractive than fish, or scampi. However, in a comparison between crushed representatives of three crab genera, no significant differences in the ability to attract Orchomene nanus were detected. Live Carcinus maenas attracted no Orchomene nanus. Crab limbs were as attractive as crab bodies minus limbs. Freshly dead crabs were more attractive than dead crabs that had been leached for 6 days. Fifty percent of Orchomene nanus survived 27 days in situ without extraneous food (although cannibalistic possibilities cannot be ruled out); a facility that would help overcome interludes of food shortage. All size-categories of Orchomene nanus were attracted to crab bait. Orchomene nanus is thus an unusual species: a diminutive, selective (and possibly obligate) scavenger specializing on high quality carrion.

Static and Functional Anatomy of the Cardiovascular System of the Portunid Crab Portunus pelagicus (Linnaeus). Part A. Static Anatomy

ABSTRACT The position, relative dimensions, and anatomical relationships of the heart (ventricle), cor frontale, and main arteries of Portunus pelagicus are described in detail, based on radiographs, detailed dissection, and histology. Brief descriptions are also provided of the pericardium, branchial sinuses, and general body hemolymph sinuses. Total fluid content and hemolymph volume were calculated as 66.5% (SD = 5.3%, N = 10) and 30.4% (SD = 3%, N = 8) of the crab's body displacement volume.

Incidence of Vibrio species associated with blue crabs (Callinectes sapidus) collected from Galveston Bay, Texas.

Bacteria were readily isolated from the hemolymph of a majority (88%) of the blue crabs collected from Galveston Bay, Texas. The hemolymph of most crabs contained moderate (greater than 10(3) bacteria/ml) to heavy (greater than (10(5) bacteria/ml) infections. Large variances were observed in the bacterial number associated with individual crabs, but no significant difference was observed between the mean bacterial levels in the hemolymph of crabs collected during different seasons of the sampling year. Vibrio spp. were the predominant bacterial types in the hemolymph of infected crabs and increased in number significantly during the summer season. Warmer water temperatures were thought to be responsible for this increase. Bacterial numbers and the percentage of Vibrio spp. were highest in the interior of the crab bodies, especially in the digestive tract. The exterior of the crabs did not appear to be the source of the hemolymph's bacterial flora. Bacteria taxonomically identical to Vibrio cholerae. V. vulnificus, and V. parahaemolyticus were routinely isolated from the crab hemolymph and external carapace. V. parahaemolyticus was the most prevalent of the pathogenic Vibrio spp. and was isolated from 23% of the hemolymph samples. V. vulnificus (7%) and V. cholerae (2%) occurred less commonly in the hemolymph. The incidences of V. parachaemolyticus and V. vulnificus were related and increased in the summer months. Both organisms were frequently isolated from the same crab.