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PubMed2005

Respiratory and acid-base responses during migration and to exercise by the terrestrial crab Discoplax (Cardisoma) hirtipes, with regard to season, humidity and behaviour.

The terrestrial crab Discoplax hirtipes (formerly Cardisoma hirtipes) exhibits a seasonally dichotomous activity pattern governed by the seasonal rainfall on Christmas Island, with a breeding migration in the wet season. Greater activity in the wet season reflects a release of constraints on ion and water balance independent of changes in exercise physiology. The respiratory responses to walking exercise by D. hirtipes were assessed with regard to humidity and season. In the laboratory, crabs walked 38% faster when humidity was high, while the O(2) uptake across the lung became diffusion limited despite a Ca(2+)-induced increase in O(2) affinity of the haemocyanin. Crabs walking in 90% relative humidity exhibited a larger metabolic acidosis while re-oxidation of l-lactate was only 0.49 mmol l(-1) h(-1). The wet-season crabs were more active and exhibited a respiratory acidosis compared with the quiescent dry-season crabs. The migration was close to the limit of the aerobic scope of the crabs, and the pulmonary oxygen partial pressure (P(O(2))) was depressed, the O(2) uptake diffusion limited and the arterial-venous P(O(2)) difference diminished. Additional, enforced exercise induced a metabolic acidosis. The optimum strategy for migration would be walking continuously but at a speed within the aerobic scope. D. hirtipes is influenced by seasonal rain and responds to lower ambient humidity by limiting exercise. The behavioural response is paramount since the changes in respiratory status were determined primarily by the differences in commitment to, and investment in, walking and not by direct effects of humidity on respiratory physiology.

Analysis of Variance↗
PubMed1997

Perireceptor mechanisms sustaining olfaction at low salinities: insight from the euryhaline blue crab Callinectes sapidus

As the blue crab Callinectes sapidus moves from sea water to fresh water, the 'exposed' chemosensory dendrites in the olfactory sensilla (aesthetascs) undergo changes in length that are positively correlated with environmental salinity. In this study, we demonstrate the following. (1) The responses of the olfactory receptor cells of freshwater-acclimated crabs are reduced relative to those of seawater-acclimated animals, but increase with a time course comparable to the increase in dendrite length when these crabs are transferred to sea water. (2) The olfactory response of seawater-acclimated crabs is lost and the chemosensory dendrites osmotically ablated if the aesthetascs are acutely exposed to low salinity. However, maintaining iso-osmotic conditions with mannitol preserves both the physiological response and the structural integrity of the dendrites. (3) The flux of [14C]thiocyanate and 22Na between the hemolymph and sensillar lymph of the aesthetascs indicates continuity between these fluid compartments. (4) There is a net efflux of Na+ from the hemolymph through the aesthetascs in freshwater-acclimated crabs, and measurements of electrical potential across the antennules suggest that this efflux largely derives from passive diffusion. (5) Dendrites in the aesthetascs of crabs acclimated to brackish water are intermediate in length between those of freshwater- and seawater-acclimated animals. Together, our findings suggest that, at low salinities, the efflux of Na+ (and probably other ions) from the hemolymph generates an ionic/osmotic microenvironment within the aesthetascs that sustains the structural and functional integrity of the olfactory dendrites. We propose that the length of these dendrites, and consequently the olfactory response, is constrained by the distance over which this microenvironment can be effectively maintained.

Journal Article↗
PubMed1996

Establishing tolerable dungeness crab (Cancer magister) and razor clam (Siliqua patula) domoic acid contaminant levels.

Domoic acid has been found in razor clams (Siliqua patula) and dungeness crabs (Cancer magister) in Washington State and elsewhere on the West Coast of the United States. Due to toxic effects associated with domoic acid exposure, an effort has been made to establish tolerable domoic acid levels in crabs and clams obtained from commercial harvest and sale and from individual recreational harvesting. To accomplish this, the amount of clams and crabs consumed by populations of concern was determined, a tolerable daily intake (TDI) was developed for individuals most sensitive to effects of this compound, and the TDI was equated with consumption patterns to determine tolerable clam and crab domoic acid levels. Results indicate that the primary health effects associated with domoic acid toxicity can be averted in populations of concern and for others consuming crabs or clams less frequently (or in lesser quantity) if domoic acid contaminant concentration does not exceed 30 mg/kg in the hepatopancreas and viscera of dungeness crabs or 20 mg/kg in clams.

Animals↗
PubMed2002

Evaluation of insecticide impregnated baits for control of mosquito larvae in land crab burrows on French Polynesian atolls.

Land crab burrows are larval mosquito habitats of major significance in the Pacific region. They are constituted by a sinuous tunnel leading to a chamber in contact with the water table, where mosquito larvae proliferate. Controlling larvae in these sites is difficult, because the configuration of burrows prevents the use of standard techniques. An experiment was carried out in French Polynesia to control Aedes polynesiensis Marks and Culex spp. breeding in burrows of the land crab Cardisoma carnifex (Herbst). The technique was based on the crab's behavior, which involves the crab carrying food into its burrow. It was shown that appetizing baits impregnated with an insecticide were carried by crabs into the flooded chamber of their burrows. A field treatment of burrows was carried out by sowing insecticide impregnated baits on the ground. The treatment coverage was almost perfect and the easy implementation of the technique enabled large areas to be treated in a short time. The bait was developed by compacting various flours, which easily incorporate a large variety of insecticide formulations. Although the baits can be easily stocked, a reliable insecticide is still to be found. The results indicate that our technique could be a method of choice for treating crab burrows.

Aedes↗
PubMed2005

Effects of the Briarosaccus callosus infestation on the commercial golden king crab Lithodes aequispina.

Commercial crab populations off the Kamchatka coasts are infested to a considerable degree by the rhizocephalan parasite Briarosaccus callosus: of 769 Lithodes aequispina males examined, 43 (5.7%) were parasitized. Infestations result in the feminization of the crabs, a significant decrease in the cheliped length, and a significant decrease in the carapace length and width. We suggest that commercial selection of healthy males, and the returning of unsuitable crabs, including infested ones, back into the sea, results in an increase of the proportion of infested crabs in the population, their elimination from reproduction, and, eventually, the gradual degradation of a whole population. To minimize as far as possible the negative effects of commercial crab harvesting, all infested crab specimens caught must be destroyed, either aboard or elsewhere, instead of throwing them back into the sea.

Animals↗
PubMed2005

Behavioral and electrophysiological experiments suggest that the antennular outer flagellum is the site of pheromone reception in the male helmet crab Telmessus cheiragonus.

Sexually competent females of Telmessus cheiragonus (helmet crab) release two pheromones that elicit grasping and copulation behaviors in males (Kamio et al., 2000, 2002, 2003). Our study aimed to use behavioral and electrophysiological techniques to identify the site of reception of these sex pheromones. In behavioral experiments, either the inner or the outer flagella of the antennules were ablated bilaterally from male crabs, and responses of male crabs to female odor were examined. When the inner flagella were surgically ablated, the sexual response (i.e., grasping and copulation behavior) of male crabs was not significantly changed relative to control animals that had their second antennae ablated. In contrast, the sexual response was significantly reduced when the outer flagella of the antennules were ablated, suggesting that the outer flagellum is the receptor organ that detects the sex pheromones. In electrophysiological experiments, urine, which in females contains the pheromone that elicits grasping behavior by males but does not contain the pheromone eliciting copulation, whose release site is not known, was tested. Female and male urine as well as shrimp extract evoked phasic responses of chemosensory afferents innervating aesthetasc sensilla on the outer flagellum of male crabs. The response of the afferents had significantly higher magnitude and lower threshold when female urine was applied. Thus, behavioral and electrophysiological observations suggest that in male helmet crabs, the outer flagellum of the antennule is the chemosensory organ that detects female sex pheromone.

Animals↗
PubMed2006

Immune defense reduces respiratory fitness in Callinectes sapidus, the Atlantic blue crab.

Crustacean gills function in gas exchange, ion transport, and immune defense against microbial pathogens. Hemocyte aggregates that form in response to microbial pathogens become trapped in the fine vasculature of the gill, leading to the suggestion by others that respiration and ion regulation might by impaired during the course of an immune response. In the present study, injection of the pathogenic bacterium Vibrio campbellii into Callinectes sapidus, the Atlantic blue crab, caused a dramatic decline in oxygen uptake from 4.53 to 2.56 micromol g-1 h-1. This decline in oxygen uptake is associated with a large decrease in postbranchial PO2, from 16.2 (+/-0.46 SEM, n=7) to 13.1 kPa (+/-0.77 SEM, n=9), while prebranchial PO2 remains unchanged. In addition, injection of Vibrio results in the disappearance of a pH change across the gills, an indication of reduced CO2 excretion. The hemolymph hydrostatic pressure change across the gill circulation increases nearly 2-fold in Vibrio-injected crabs compared with a negligible change in pressure across the gill circulation in saline-injected, control crabs. This change, in combination with stability of heart rate and branchial chamber pressure, is indicative of a significant increase in vascular resistance across the gills that is induced by hemocyte nodule formation. A healthy, active blue crab can eliminate most invading bacteria, but the respiratory function of the gills is impaired. Thus, when blue crabs are engaged in the immune response, they are less equipped to engage in oxygen-fueled activities such as predator avoidance, prey capture, and migration. Furthermore, crabs are less fit to invade environments that are hypoxic.

Animals↗
PubMed2006

Effect of salinity on osmoregulatory patch epithelia in gills of the blue crab Callinectes sapidus.

In euryhaline crabs, ion-transporting cells are clustered into osmoregulatory patches on the lamellae of the posterior gills. To examine changes in the branchial osmoregulatory patch in the blue crab Callinectes sapidus in response to change in salinity and to correlate these changes with other osmoregulatory responses, crabs were acclimated to a range of salinities between 10 and 35 ppt. When crabs that had been acclimated to 35 ppt were subsequently transferred to 10 ppt, both the size of the osmoregulatory patch on individual gill lamellae and the specific activity of Na+, K+-ATPase in whole-gill homogenates increased only after the first 24 h of exposure to dilute seawater. Enzyme activity and size of patch area increased gradually and reached their maxima (increasing by 200% and 60%, respectively) 6 days following transfer to 10 ppt seawater and then remained at these levels. Patch size at acclimation varied inversely with the salinity for seawater dilutions below 26 ppt (the isosmotic point of the crab), although it did not vary in salinities at or above 26 ppt. Thus, the size of the patch clearly is modulated with acclimation salinity, but it increases only in those salinities in which the crab hyperosmoregulates. An increase in the total RNA/DNA ratio in gill homogenates, the lack of mitotic figures in the lamellae, and the lack of incorporation of bromodeoxyuridine into nuclei of lamellar epithelial cells during acclimation to dilute seawater were interpreted as evidence that no cell proliferation had occurred and that increases in the size of the osmoregulatory patch occurred through differentiation of existing gas exchange cells or of undifferentiated epithelial cells into ion-transporting cells.

Adaptation, Physiological↗
PubMed2002

The East African decapod crab Neosarmatium meinerti (de Man) sweeps mangrove floors clean of leaf litter.

Leaf litter removal by the abundant mangrove decapod crab Neosarmatium meinerti was studied in series of field and laboratory experiments in East Africa. In the high intertidal Avicennia marina zone crabs buried all leaves placed on the forest floor and consumed on average 67% of them within 2 hrs. High shore crabs in Kenya buried 4 g m(-2) leaf-litter in 1 hr, i.e. approx. twice the daily litter fall. In contrast, in the low shore Sonneratia alba zone, where typical leaf-eating crabs were absent, none of the offered leaves showed signs of herbivory. Leaf choice experiments in the laboratory showed that N. meinerti preferred some species to others. Leaf consumption per gram crab was higher in females than males. The laboratory studies also indicated that crabs could consume substantially more than the average daily litter fall. Video recordings documented frequent fights to gain or retain fallen leaves, suggesting strong competition for leaf litter. Earlier studies indicating that N. meinerti may sweep mangrove forest floors clean of leaf litter are confirmed. In high shore mangroves of East and South Africa where N. meinerti is common, energy flow appears unique: virtually all litter production is retained.

Animals↗
PubMedDate not supplied

Liquid chromatography/tandem mass spectrometry analysis of chloramphenicol in cooked crab meat.

A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method is described for the extraction, cleanup, determination, and confirmation of chloramphenicol (CAP) in cooked crab meat. The method involves pulverization of cooked crab meat with dry ice; extraction of the CAP into ethyl acetate (EtOAc); evaporation (by N2) of the EtOAc; addition of methanol, aqueous NaCl, and heptane; extraction of the lipids into the heptane, followed by extraction of the aqueous phase with EtOAc; evaporation (by N2) of the EtOAc; dissolution into methanol-water; filtration; and separation/detection/confirmation using LC/MS/MS. Crab meat was fortified at 0.25, 0.50, and 1.0 ng/g (ppb) chloramphenicol. Average absolute recoveries were 67, 84, and 86%, respectively, with relative standard deviation values all less than 1%. Four daughter ions (m/z 152, 176, 194, and 257) were monitored off the m/z 321 precursor ion. Determination was based on a standard curve using the peak areas of the m/z 152 daughter ion (the base peak) for standard solutions equivalent to 0.10, 0.20, 0.50, and 1.0 ppb in tissue (made with control crab extract). A set of 6 matrix controls (unfortified crab meat) was also analyzed, in which no chloramphenicol was detected. For identification purposes, the ion ratios (of each daughter ion versus the base daughter ion) of the fortified crab versus those of the chloramphenicol standards agreed within 10% (relative) at fortified chloramphenicol concentrations of 0.25-1.0 ppb.

Acetates↗
PubMed1998

A method for assessing the effects of runneling on salt marsh grapsid crab populations.

Runneling, a type of habitat modification using shallow channels, is an effective method for controlling mosquitoes that breed in intertidal salt marshes. Grapsid crab populations were studied to assess the environmental effects of runneling on nontarget species. Pitfall traps provided a means of monitoring crab distribution and relative abundance at Coomera Island in southeastern Queensland. The study indicated that although runneling does not have a significant effect on the total number of crabs, it may have a significant impact on species distribution. Significantly greater numbers of Parasesarma erythrodactyla were found at the runneled site. In contrast, Helograpsus haswellianus was more abundant at the unrunneled control site. Associations were also found between species abundance, distance from the tidal inlet, and vegetation type. Helograpsus haswellianus was associated with mixed vegetation, whereas Parasesarma erythrodactyla was associated with tall, dense salt marsh couch. No correlation was found between the number of crab burrows present at the study site and the number of crabs caught in the traps. However, the runneled site had approximately twice the number of crab burrows of the unrunneled control site. These results were consistent for 3 consecutive monthly sampling periods. The method has proven suitable for further studies on the long-term environmental impact of runneling.

Animals↗
PubMed2003

Chemical attractants in horseshoe crab, Limulus polyphemus, eggs: the potential for an artificial bait.

Horseshoe crabs, Limulus polyphemus, are the preferred bait in the eel and conch fisheries along the east coast of the United States. However, recent management measures have restricted the availability of horseshoe crabs to commercial fisheries, creating the need for sustainable, alternative bait sources. In this study, we examined the chemistry underlying the predator-prey attraction to determine if specific, isolable attractant metabolites from the horseshoe crab could be identified and characterized for incorporation into an artifical bait. Initial assays with the mud snail, Hyanassa obsoleta, suggested that the chemoattractants were concentrated in L. polyphemus eggs. Chemical analyses and biological assays of the egg extract indicated the primary cue was a heat-stable, proteinaceous compound (>10 kDa). A carbohydrate-rich fraction of low molecular mass (< 10 kDa) also enhanced mud snail chemotaxis. Analysis of egg digests with SDS-PAGE confirmed the presence of glycoproteins or carbohydrate-binding proteins in the horseshoe crab egg extract. Because the attractant appears to be a complex protein or glycoprotein, conventional chemical synthesis is unlikely. However, the tools of modem biotechnology offer the potential to produce this attractant in a system independent of the horseshoe crab. Such an attractant could be incorporated into an artificial bait, providing an ecologically sound alternative for commercial eel and whelk fisheries.

Animals↗
PubMed1984

The amino acid sequence of coagulogen isolated from southeast Asian horseshoe crab, Tachypleus gigas.

The amino acid sequence of coagulogen isolated from Southeast Asian horseshoe crab (Tachypleus gigas) has been determined. The NH2-terminal sequence of the first 51 residues was obtained by automated Edman degradation. The intact protein was then treated with a Tachypleus clotting enzyme, to form a gel and to remove an internal peptide C (28 residues) located near the NH2-terminal portion. The gel protein, which consisted of A chain (18 residues) and B chain (129 residues), was S-alkylated and the resulting two chains were separated by acetone precipitation. Among these segments, A chain and peptide C were assigned to the NH2-terminal portion of whole coagulogen, as judged from their amino acid compositions. On the other hand, the covalent structure of B chain was determined by sequencing the peptides obtained from its tryptic digest. The alignments of the tryptic peptides were deduced from the sequence homology in comparison with the previously established B chain sequence of Japanese horseshoe crab (T. tridentatus) coagulogen. T. gigas coagulogen had a total of 175 amino acids and a calculated molecular weight of 19,770. When the sequence was compared with those of Japanese and American horseshoe crab (Limulus polyphemus) coagulogens, extensive structural homology was found: T. tridentatus/T. gigas, 87% and L. polyphemus/T. gigas, 67%. This comparison suggests that Japanese and Southeast Asian horseshoe crabs have a crab, based on amino acid sequence data.

Amino Acid Sequence↗
PubMed1990

Concurrent protein synthesis is required for in vivo chitin synthesis in postmolt blue crabs.

Chitin synthesis in crustaceans involves the deposition of a protein-polysaccharide complex at the apical surface of epithelial cells which secrete the cuticle or exoskeleton. The present study involves an examination of in vivo incorporation of radiolabeled amino acids and amino sugars into the cuticle of postmolt blue crabs, Callinectes sapidus. Rates of incorporation of both 3H leucine and 3H threonine were linear with respect to time of incubation. Incorporation of 3H threonine into the endocuticle was inhibited greater than 90% in the presence of the protein synthesis inhibitor, puromycin. Linear incorporation of 14C glucosamine into the cuticle was also demonstrated; a significant improvement of radiolabeling was achieved by using 14C-N-acetylglucosamine as the labeled precursor. Incorporation of 3H-N-acetylglucosamine into the cuticle of postmolt blue crabs was inhibited 89% by puromycin, indicating that concurrent protein synthesis is required for the deposition of chitin in the blue crab. Autoradiographic analysis of control vs. puromycin-treated crabs indicates that puromycin totally blocks labeling of the new endocuticle with 3H glucosamine. These results are consistent with the notion that crustacean chitin is synthesized as a protein-polysaccharide complex. Analysis of the postmolt and intermolt blue crab cuticle indicates that the exoskeleton contains about 60% protein and 40% chitin. The predominant amino acids are arginine, glutamic acid, alanine, aspartic acid, and threonine.

Amino Acids↗
PubMed2004

Hepatopancreas gluconeogenesis during anoxia and post-anoxia recovery in Chasmagnathus granulata crabs maintained on high-protein or carbohydrate-rich diets.

C. granulata is a semiterrestrial crab that lives in the mesolittoral and the supralittoral zones of estuaries and faces hypoxia and anoxia when exposed to atmospheric air. The carbohydrate or protein content of the diets administered to the crabs induced different metabolic adjustments during anoxia and post-anoxia recovery period. During the first hour in anoxia a marked increase in L-lactate concentration in hemolymph was induced, followed by a reduction in its levels accompanied by two peaks in hepatopancreas gluconeogenic capacity. Anoxia exposure did not induce a reduction in the hepatopancreas phosphoenolpyruvate carboxykinase activity in either dietary group. Our results suggest that in anaerobiosis this crab uses the conversion of lactate to glucose in hepatopancreas to maintain the acid-base balance and the glucose supply. In post-anoxia recovery, the fate of L-lactate is the hepatopancreas gluconeogenesis in high protein maintained crabs. On the other hand, in the crabs maintained on carbohydrate-rich diet the L-lactate levels decreased gradually in the hemolymph during the post-anoxia recovery; however, the hepatopancreas gluconeogenesis did not increase. In both dietary groups, an increase in the gluconeogenic capacity of hepatopancreas occurred at 30 h of post-anoxia recovery.

Anaerobiosis↗
PubMed2006

Neuroendocrine regulation of carbonic anhydrase expression in the gills of the euryhaline green crab, Carcinus maenas.

The relationship between branchial carbonic anhydrase (CA) activity, CA gene expression and salinity, and potential mechanisms of regulation, was investigated in the euryhaline green crab, Carcinus maenas, acclimated to 33 ppt and transferred to 10 ppt, and the stenohaline rock crab, Cancer irroratus, acclimated to 32 ppt and transferred to 18 ppt. CA activity in green crabs acclimated to high and low salinity was a function of CA mRNA expression, with low salinity exposure resulting in an increase in both CA expression and activity. Eyestalk ablation (ESA) in green crabs acclimated to high salinity resulted in an increase in CA expression in the posterior, ion-transporting gills, in the absence of the low salinity stimulus. There were no changes in CA activity or expression in the anterior, respiratory gills. ESA also potentiated low salinity-stimulated CA induction, again, only in posterior gills. There were no changes in CA activity in any gills of Cancer irroratus, in response to either ESA or low salinity. These results suggest that CA expression in euryhaline, osmoregulating species, is under inhibitory regulation by a putative repressor found in the eyestalk, and that this mechanism is absent in stenohaline, osmoconforming species. CA expression is maintained at low, baseline levels in crabs acclimated to high salinity by the presence and action of this compound. The effects of the repressor appear to be reduced upon exposure to low salinity, allowing CA induction to occur.

Animals↗
PubMed2003

Instability of crab vitellogenin and its immunological relatedness with mammalian atherogenic lipoproteins.

Vitellogenesis is the process of accumulation of vitellogenin (Vg) in rapidly growing oocytes of oviparous animals and its' subsequent transformation into lipovitellin (Lv). Lipovitellin, which forms the major yolk protein, serves as a principal nutrient reserve for the developing embryo. In the present study, Vg and Lv were purified from the hemolymph and ovary, respectively of the crab Scylla serrata by gel filtration followed by preparative gel electrophoresis. It was observed that purified Vg, but not Lv, possessed an intrinsic protease activity with which it underwent autoproteolysis giving rise to several smaller proteins. Furthermore, urea-mediated unfolding studies by UV-spectral analysis revealed clearly that Vg was easily disrupted by urea whereas Lv was resistant. Taken together, these results suggest that although Lv had a stable conformation, its precursor Vg was labile and highly sensitive to degradation. Another aspect that was investigated in the present study was the immunological kinship of crab Vg and Lv to mammalian atherogenic lipoproteins, the low density lipoprotein (LDL), very low density lipoprotein (VLDL), and apolipoprotein B (apoB). By Western blot analysis, it was demonstrated that crab Vg and Lv were immunoreactive to antibodies to human LDL, VLDL, and apoB. These observations suggest the existence of common epitope recognition sites in crab Vg and mammalian lipid transferring proteins. This corroborates well with our earlier study on the recognition of crab Vg receptor by mammalian lipoproteins.

Animals↗
PubMed1987

Structure and function of the hemocyanin from a semi-terrestrial crab, Ocypode quadrata.

Structural and functional studies of the hemocyanin of the semi-terrestrial ghost crab, Ocypode quadrata, demonstrate a variety of differences in comparison to the hemocyanin of aquatic crabs. These differences may be related to the terrestrial habit of this crab. Unlike aquatic crabs, the major (56%) blood component is the hexamer; the remaining 44% is dodecamer. The hexamers and dodecamers are not in rapid equilibrium. Electrophoretic analysis of the subunit composition indicates three major components referred to as 1, 3, and 4, and one minor component referred to as component 2. These components, although electrophoretically distinct, are alike immunologically. Components 1 and 2 are essentially absent from purified hexamers, whereas they compose 1/3 of the subunits in dodecamers. These results suggest that they are involved in linking hexamers to form dodecamers, and that two, rather than one, subunits are involved in the bridge. Oxygen-binding measurements show a higher degree of cooperativity, and a much reduced allosteric effect of L-lactate on the dialyzed hemocyanin as compared to the hemocyanin of aquatic crabs. Exercise rapidly induces a large drop in hemolymph pH (0.5 units) and a corresponding increase in lactate concentrations (to 10 mM).

Allosteric Regulation↗