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At least 19 recordsLinked to original sources
PubMed1992

Evolution of king crabs from hermit crab ancestors.

King crabs (Family Lithodidae) are among the world's largest arthropods, having a crab-like morphology and a strongly calcified exoskeleton. The hermit crabs, by contrast, have depended on gastropod shells for protection for over 150 million years. Shell-living has constrained the morphological evolution of hermit crabs by requiring a decalcified asymmetrical abdomen capable of coiling into gastropod shells and by preventing crabs from growing past the size of the largest available shells. Whereas reduction in shell-living and acquisition of a crab-like morphology (carcinization) has taken place independently in several hermit crab lineages, and most dramatically in king crabs, the rate at which this process has occurred was entirely unknown. We present molecular evidence that king crabs are not only descended from hermit crabs, but are nested within the hermit crab genus Pagurus. We estimate that loss of the shell-living habit and the complete carcinization of king crabs has taken between 13 and 25 million years.

Animals↗
PubMed1979

Starfish and horseshoe crab egg factors cause elevations of cyclic nucleotide concentrations in spermatozoa from starfish and horseshoe crabs.

Factors collected from the eggs of the starfish (Pisaster giganteus) and the horsehoe crab (Limulus polyphemus) caused significant increases in the sperm cyclic nucleotide concentrations of the respective species. Sea urchin egg factors, at concentrations that resulted in maximal cyclic nucleotide elevations in sea urchin spermatozoa, had no effect on those of starfish or horseshoe crab, suggesting a species specificity with respect to egg factor-induced changes in sperm cyclic nucleotide metabolism.

Animals↗
PubMed1991

Preliminary results on the seasonality and life cycle of the parasitic dinoflagellate causing bitter crab disease in Alaskan tanner crabs (Chionoecetes bairdi).

Tanner crabs (Chionoecetes bairdi) from the Sullivan Island area of southeast Alaska were sampled for 1 year to determine the prevalence and intensity of the parasitic dinoflagellate which causes bitter crab disease (BCD). The prevalence and intensity of infection were the greatest in the summer, declined in the fall and winter, and increased again in the spring. A possible relationship between softer, newer shells and higher levels of parasitism was also observed. In vivo transmission studies in the laboratory suggested there are several morphologically different forms of the vegetative cell of the BCD dinoflagellate which occur prior to sporulation of the parasite. In addition, it appears that both the two spore types produced by the parasite are infectious by injection and that there is no ploidy difference between the two spore types and the vegetative cell, suggesting that the two spore types may not represent separate sexes.

Animals↗
PubMed1978

Studies on the immature stages of the Simulium neavei Roubaud complex and their associated crabs in the Eastern Usambara Mountains in Tanzania. IV. Observations on the crabs and their attached larvae under exceptionally dry conditions.

When exceptionally low rainfall resulted in the drying out of some 'permanent' streams containing the immature stages of Simulium neavei complex species, the fate of the larvae and their associated crabs was investigated. Both crabs and larvae survived under rocks, stones and boulders where some moisture persisted. Such situations would be out of reach to insecticides applied to running water in the normal way.

Animals↗
PubMed1992

Purification and characterization of vitellogenin and lipovitellins of the sand crab Emerita asiatica: molecular aspects of crab yolk proteins.

In the mole crab Emerita asiatica, the main yolk proteins consist of two slow moving lipovitellins (Lv I and Lv II) of glycolipoprotein nature. Lv I cleaves into subunits (MW: 109,000 and 105,000) and Lv II gives rise to six subunits (MW: 65,000, 54,000, 50,000, 47,000, 44,000, and 42,000) in SDS-PAGE (with beta-mercaptoethanol). In order to observe the stability of Lv II as well as to achieve better resolution of the proteins, two different buffer systems (Phosphate buffered saline and tris-buffered saline), 40% sucrose, and glass distilled water were used as homogenizing media. Among them, better resolution was achieved with tris-buffered saline and 40% sucrose, and tris-buffered saline seems to be the ideal medium for elution of Lv II. The analysis of biochemical constituents of the major Lv II reveals a percentage composition of 69.325, 27.927, and 2.753 respectively for protein, lipid, and bound sugars. In the I stage embryo, protein comprises about 67.276%, lipid 29.65%, and bound sugars 3.015%. Vitellogenin (Vg) electrophoretically corresponding to the Lv I and Lv II was present in the female haemolymph during the entire period of embryogenesis. The number of subunits (8) of Vg in all stages remained unaltered and their approximate molecular weights were Vg1, 91,000; Vg2, 87,000; Vg3, 83,000; Vg4, 61,000; Vg5, 58,000; Vg6, 45,000; Vg7, 42,000; and Vg8, 38,000. Different proteins present in the embryos (I and IV stage) and the serum obtained from the animal carrying the I stage embryo were separated by gel-filtration in high performance liquid chromatography (HPLC). Sephadex (G-200) gel filtration chromatography was used to purify the Lv II in large quantity. Total lipid extracted from Lv II as well as the embryos belonging to different stages of development were separated into their constituent neutral, glycolipids, and phospholipids, using silicic acid column chromatography. Thin layer chromatography (TLC) was used to isolate the different phospholipids purified from various stages of embryos and Lv II. As many as seven different phospholipids were separated from Lv II and I and IX stage embryos; and whereas thin layer chromatogram of V and VI stage embryos showed six different phospholipids, embryos of VII and VIII stage contained four phospholipid species. Cholesterol, glycolipids, and individual phospholipids isolated from the Lv II and I stage embryo were quantified spectrophotometrically and the results were discussed.

Animals↗
PubMed1992

Shell disease and metal content of blue crabs, Callinectes sapidus, from the Albemarle-Pamlico Estuarine System, North Carolina.

Concentrations of 13 elements were determined for three tissues (gill, hepatopancreas, muscle) in diseased crabs from a contaminated estuary (Pamlico River, NC), and in non-diseased crabs from both the contaminated estuary and a relatively uncontaminated area (Albemarle Sound, NC) during the fall 1989 and summer 1990. The diseased crabs had lesions which completely penetrated their dorsal integument, while the non-diseased crabs lacked lesions. Sediments within the contaminated area showed enrichment of arsenic, cadmium, manganese, titanium and vanadium relative to the uncontaminated area. Levels of aluminum, arsenic, cobalt, manganese, nickel, titanium, vanadium and zinc were significantly higher in both gill and hepatopancreas in crabs from the contaminated area. Manganese was always highest in the diseased crabs in all tissues measured. The concentrations of the remaining elements were greater in the gills of diseased crabs, while highest values of these elements in the hepatopancreas varied among the diseased and non-diseased crabs from the polluted area. Conversely, copper levels were always highest in all tissues in crabs from the uncontaminated area, and typically lowest in the diseased crabs. Concentrations of aluminum and arsenic were also significantly greater in the muscle tissue of crabs from the contaminated area, but no distinct trend was evident with regard to diseased versus non-diseased crabs. Arsenic was the only element accumulated by crabs in the contaminated area which has a known toxic affect on the tissue responsible for cuticle synthesis and repair (hypodermis) in crustaceans. Metals also accumulated could possibly act synergetically to compromise normal metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Incidence of bacteremia in stressed and unstressed populations of the blue crab, Callinectes sapidus.

The incidence of bacteremia in the blue crab, Callinectes sapidus, is reported to be in excess of 80%. Because these results have been controversial, a field study was initiated to determine the effect of commercial capture and handling stresses on the incidence and levels of infection in blue crabs. The majority (75%) of "unstressed" crabs which were captured individually and bled immediately upon removal from the water were bacteremic, with a geometric mean level of infection of 14 CFU/ml of hemolymph. Crabs collected by crab pot, confined within these pots for as long as 24 h, and sampled immediately after removal from the water had a similar mean level of infection. Crabs subjected to the stresses of commercial capture, handling, and transport showed a higher incidence of infection (91%) and a mean infection level of 46 CFU/ml. Injuries sustained by crabs during commercial handling are thought to be associated with the higher incidence of infection. Vibrio spp. were primarily responsible for progressive infections in commercially stressed crabs and were the predominant bacterial type in heavily infected crabs. Our results indicated that uninjured healthy crabs do not have sterile hemolymph but instead harbor low-level bacterial infections.

Animals↗
PubMed1975

Microbiological characteristics of Dungeness crab (Cancer magister).

Aerobic, heterotropic microorganisms of Dungeness crab (Cancer magister) were isolated from raw crab, cooked crab, crab meats obtained during commercial processing, and from retail crab meat samples. Each microbial isolate was then identified to the genus level employing the revised replica plating procedure. Microbial groups most commonly isolated from crab meat were, in the order of predominance, Moraxella, Pseudomonas, Acinetobacter, Arthrobacter, Micrococcus, Flavobacterium-Cytophaga, and Bacillus sp. Proteus, Staphylococcus, yeasts, Vibrio, and Lactobacillus sp. were found less frequetly in some samples. Distribution patterns of microbial flora in crab meat revealed the presence of three classes of microorganisms. Microorganisms that originated from the raw crab and gained predominance by growth during refrigerated storage were Moraxella, Pseudomonas, Acinetobacter, and Flavobacterium-Cytophaga sp. Those that originated from the crab but did not grow in meat were Arthrobacter and Bacillus sp. Micrococcus, Staphylococcus, and Proteus sp. were introduced during processing, but they did not grow in the refrigerated crab meat.

Aerobiosis↗
PubMed1986

IgE sensitization in snow crab-processing workers.

Occupational asthma is a highly prevalent disease among snow crab-processing workers, but its immunologic mechanism has not been identified. Prick skin tests with snow crab-meat extract, commercial extracts from other crab genera, and snow crab cooking water collected in 1984 were performed on 119 workers. Crab-specific IgE was assessed by RAST in sera from 115 workers with meat and water extracts. Both skin and RAST tests were performed in 58 individuals. Diagnosis of occupational asthma had previously been confirmed in 54 individuals. A highly significant relationship was demonstrated between the presence of immediate skin reactivity or increased serum levels of specific IgE to crab extracts and the occurrence of occupational asthma. There was good agreement between the results of skin and RAST tests with extracts of either meat or snow crab cooking water. Cooking water and snow crab-meat extracts were more sensitive than commercial preparations. Water extract was more potent and more sensitive than meat extract. We conclude that there is evidence that occupational asthma in snow crab-processing workers is mediated through an IgE mechanism.

Aerosols↗
PubMed1985

Epidemiologic and immunologic studies in processors of the king crab.

Following the report of ten cases of respiratory illness in processors of frozen king crab, we investigated the conditions of work and the pulmonary and immunologic status of the workers in three crab-processing and one fish-packing (control) plant. Pulmonary function was measured before and after work, and skin tests were performed in subgroups matched for age, sex, and duration of current employment. The antibody response to king crab antigens was examined in sera from the subgroups and another (unrelated) control group. Extracts of crab meat, shell, and processing dust were used for skin testing and precipitin detection. FEV1, FVC, and MEFR decreased during the day in two crab processors, and precipitins were evident in sera from nine, but findings were normal in the fish packers. Crab meat elicited the strongest response, with multiple precipitin bands in some cases. Control sera showed no reaction. There was correlation between serology, results of skin tests, and symptoms. It is concluded that the inhalation of aerosolized crab antigen(s) may cause respiratory symptoms and can cause immunologic effects similar to those caused by other occupational respiratory allergens. We recommend preplacement and periodic medical examination of workers in crab-processing plants, improved ventilation in processing areas, and programs to discourage smoking.

Adolescent↗
PubMed1975

Kinetic investigation of unfolding and partial refolding of a crab satellite (dA-dT)n.

Crab (dA-dT)n was isolated from the testes of Cancer borealis by a procedure involving separation of DNA and segregation of the satellite fraction by Hg2+ binding/Cs2SO4 density gradient ultracentrifugation. The titration of crab (dA-dT)n samples at 10 degrees indicated a sharp absorbance change at pH 11.98 in agreement with the pHm value observed for synthetic poly(dA-dT) under identical conditions. The reversal of the titration, however, resulted only in about 50% recovery of the original absorbance (at 260 nm) in marked contrast to the complete reversibility of the synthetic material. pH-jump experiments were carried out for the purpose of characterizing the rates and mechanisms of conformational transitions brought about by changes in the solution environment. It was found that the disintegration of the putative native structure of crab (dA-dT)n starts with a very fast reaction (occurring within the 6-msec deadtime of the instrument and comprising 65% of the total absorbance change) and it is completed via a slower first-order reaction (k = 66 sec minus 1). It is postulated that the first process is due to the rapid untwisting of end regions and, perhaps, some short hairpin-like helical branches present on the macromolecules. The second reaction is believed to be the end-to-end type unwinding of the double-helical backbone of crab (dA-dT)n. In the presence of low concentration (3 mug/ml) of Hg2+ ions the overall rate of disintegration process decreased drastically. pH jumps from pH values above pHm to values below were used to study the rates of absorbance changes corresponding to the refolding of the strands of denatured crab (DA-dT)n. A concentration independent process consisting of two phases was observed. The first phase was a gradual nonexponential process spanning the first second of the reaction, and the other, a very slow first-order process characterized by the rate constant value of 0.053 sec minus 1. It is proposed that the first part of the process (involving about 24% of nucleotide residues) is an intramolecular formation of helical hairpins (frequently interrupted by mismatching bases) and the second part is a manifestation of some association of the extant unpaired bases during the folding of the branched structure. Refolded crab (dA-dT)n samples when subjected again to pH greater than pHm in the stopped-flow apparatus displayed not the disintegration pattern of the native crab (dA-dT)n but rather that of synthetic poly(dA-dT. The marked facility of crab (dA-dT)n macromolecules for rapid conformational transitions induced by slight changes in the solution environment might be relevant to the biological function of this DNA.

Animals↗
PubMed1985

Stress reduces hemolymph ecdysteroid levels in the crab: mediation by the eyestalks.

In decapod crustaceans, molt hormone (ecdysone) production by Y-organs is suppressed by an eyestalk neurosecretory product, molt-inhibiting hormone (MIH). Environmental stressors are known to delay or prevent molting in crabs. The present study assesses the function of the MIH-Y-organ neuroendocrine system in the crab Cancer antennarius under conditions of daily handling stress. After three days, stressed crabs showed significant suppression of hemolymph ecdysteroid levels, which continued to fall to 20% of controls by day 14. Ecdysteroid titers of stressed crabs returned to prestress levels seven days after stress termination. Ecdysteroid levels in de-eyestalked (DES) crabs rose 160% within 48 hr post-DES. Stressing DES crabs over 16 subsequent days did not significantly alter ecdysteroid levels compared with unstressed DES controls. Handling stress thus depresses hemolymph ecdysteroid levels in the crab, a response that is mediated by eyestalks and appears to result from stress-induced MIH release.

Animals↗
PubMed1990

The isolation and properties of collagenolytic proteases from crab hepatopancreas.

A mixture of collagenolytic proteases has been isolated from the Kamchatka crab hepatopancreas. The four individual enzymes were further separated with FPLC and partially characterized. Crab collagenolytic proteases possess a high activity against different types of collagen, especially against calf skin collagen Type III and bovine lens capsule collagen Type IV, which is resistant to the microbial Clostridium sp. collagenases. In contrast with microbial collagenases the crab enzymes are good general proteases, able to cleave standard synthetic and protein substrates and possess a chymotrypsin-, trypsin- and elastase-like specificity. N-Terminal sequence analysis revealed that crab collagenolytic proteases had evolved from a trypsin-like ancestor. Crab proteases, structurally belonging to the trypsin-like enzymes, nevertheless, possess the unique ability, among this class of enzymes, to cleave the native insoluble collagen. It seems that crab collagenolytic proteases and true metalloenzyme vertebrate and microbial collagenases have certain common structural features particularly in the regions of their substrate binding site.

Amino Acid Sequence↗
PubMed1988

Passive avoidance learning in the crab Chasmagnathus granulatus.

Male crabs Chasmagnathus granulatus were trained by means of a method similar to the standard inhibitory avoidance technique widely used in vertebrates. Each crab was placed in the dark compartment (DC) of a double-chamber device, allowed to move towards the light compartment (LC) and latency to enter measured. Experimental crabs received a shock in LC, but controls were not punished. After 1 min, both experimental and control crabs were free to return to DC. On completion of 1, 2, 3 or 24 hr intertrial interval in DC a retention test was administered and latency to enter LC was measured. A single trial was proven enough to establish a LC-shock association that was detected up to 3 hr later, but no retention was proved after 24 hr. Memory was disrupted when crabs were removed from the apparatus during the 3 hr intertrial interval. Similarities and differences between the passive avoidance method used with crabs and that used with vertebrates are discussed.

Animals↗
PubMed1989

Toxins extracted from Australian specimens of the crab, Eriphia sebana (Xanthidae).

Aqueous extracts of 75 specimens of the xanthid crab, Eriphia sebana, collected from coral reefs in the Capricorn Group, Great Barrier Reef, Australia, were assayed for toxicity to mice. Thirty-five extracts contained detectable toxicity. Toxicity was quantified by i.p. injection of mice where 1 mouse unit (MU) was defined as the amount of toxin required to kill a 20 g mouse in 15 min. Twenty-four of the extracts induced signs in mice similar to signs expected if paralytic shellfish toxins (PSTs) or tetrodotoxin were the predominant toxins. The highest toxicity found was 887.4 MU from a 98.6 g crab (= 9.0 MU/g). Purification of five combined groups of extracts from crabs collected at the same time and area revealed for the first time the presence in E. sebana of toxins similar to PSTs. TLC and electrophoretic studies showed that these toxins behaved like saxitoxin, neosaxitoxin, gonyautoxin-1 and gonyautoxin-2. Two of these groups of extracts contained only one of these PST-like toxins and the remainder contained two. Eleven of the extracts caused signs in injected mice dissimilar to signs induced by PSTs or tetrodotoxin. Foregut contents of 33 crabs contained fish, crustacean and algal remains. Crustacean remains in one gut content sample included carapace fragments bearing distinctive surface features found on the smaller toxic xanthids, Actaeodes tomentosus and Pilodius areolatus. The combined gut contents of these crabs weighed 10.4 g and the aqueous extract of which contained 4.4 MU/g of toxin, supporting the suggestion of a probable dietary origin of the toxins present in the crabs.

Animals↗
PubMed1986

Disturbance of a met-enkephalin-like hormone in the hepatopancreas of crabs contaminated by metals.

This study combines trace-metal analysis with an immunofluorescent detection of a methionine-enkephalin-like substance in the digestive gland of the shore crab, Carcinus maenas L. The crabs were taken from two sites: Saint Nazaire and Le Croisic, the first being polluted in comparison to the second. The experimental crabs were also taken in Le Croisic and contaminated with Cd, Pb, Cu, and Zn during 1 to 3 weeks in the laboratory. The immunohistological observations indicate a change in the localization of the immunofluorescent methionine-enkephalin-like substance in the cells of the tubules constituting the digestive gland. In crabs from the clean site, experimentally starved or not, the immunofluorescence appears mostly basal while it exhibits an apical localization in metal-contaminated crabs or crabs caught in the polluted area. The detected substance, the nature of which remains unknown, accompanies cytoplasmic secretory granules during their migration to the cellular apex preceding the apocrine secretion. This change of the immunoreactivity enables the detection of metal contamination but it is nonspecific and therefore, a general environment pollution could produce the same phenomenon. In the particular case of zinc, this alteration appears at a Zn concentration in seawater which does not disturb the natural level of this essential metal in the digestive gland of C. maenas.

Animals↗