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At least 19 recordsLinked to original sources
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↗
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↗
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↗
PubMed1979

[Kinetic parameters of Na,K-ATPase in the gills of crabs adapted to freshened sea water].

The dependence of Na,K-ATPase activity on concentrations of ATP, Na+, K+, Mg2+ and ouabain in the membrane preparations of crab gills was studied. The first group of crabs was adapted to freshened (25%) and the second one--to normal (100%) sea water. A 40-day adaptation of crabs to the freshened sea water results in an increase of maximal activity of Na,K-ATPase, but does not affect the enzyme affinity for ATP, Na+, K+, Mg2+ and ouabain, as well as its cooperative properties. It is assumed that adaptation of crabs to freshened sea water is accompanied by an accumulation of Na, K-ATPase in the epithelial cell membranes or crab gills without causing any qualitative changes of the enzyme.

Acclimatization↗
PubMed1977

[On the distribution of the lung flukes, Paragonimus africanus and P. uterobilateralis, in the South West Province of Cameroon and in Eastern Nigeria as determined by examination of the intermediate crab hosts for infection with metacercariae (author's transl)].

During 1973-75 the distribution of the lung flukes, Paragonimus africanus and P. uterobilateralis, was studied in South West-Cameroon and in Eastern Nigeria, on the basis of parasitological examinations of the intermediate crab hosts Sudanonautes africanus, S. pelii, and S. aubryi, belonging to the family Potamonidae. 1000 freashwater crabs from 80 localities were examined for prevalence and intensity of infection with Paragonimus methacercariae. In Cameroon S. pelii was found to be a new intermediate host for P. uterobilateralis, and S. aubryi a new host for P. africanus. The morphology, behavior, and habitats of the crabs are summarized. In Eastern Nigeria only metacercariae of P. uterobilateralis were found. The main endemic area was located in the basin of the upper Imo River. Outside this area infected crabs were found only in and around Arochukwu, in the lower tributaries of the Cross River. This distribution differs from that given by Nwokolo (1974), which was based on the origin of clinical cases. These differences are discussed. In South West-Cameroon both Paragonimus species were found. The highest prevalence and intensity of metacercariae of P. africanus was seen in certain tributaries of the Mungo River in the area of Lower Bakossi. Proceeding northwards towards Mamfe, infections with P. africanus decreased steadily, whereas infections with P. uterobilateralis increased. On the upper reaches of the Cross River from the region around Mamfe and extending as far as the Nigerian fronter at Ekok, the crabs were infected exclusively with P. uterobilateralis. The unexplored mildle reaches of the Cross River may form a bridge between the endemic areas of this lung fluke in Nigeria and Cameroon.

Animals↗
PubMed1978

Histochemical studies on the morphology of the Golgi apparatus and its relation to catecholamine biosynthesis in the locus coeruleus of Rhesus and crab-eating monkeys.

Detailed histochemical studies have been conducted on the distribution of thiamine pyrophosphatase (TPPase), L-gulonolactone oxidase (GLO), and NAD-linked xylitol dehydrogenase (XDH) in every component of the Locus coeruleus (LC) of healthy adult male Rhesus and crab-eating monkeys in order to clearify the morphology of the Golgi apparatus (GA) and its relation to biosynthesis of catechol-amines in this special nucleus of the primate (NA nucleus A 6 as defined in the Rhesus monkey by German and Bowden [1975]). Medium-sized neurons of both species of monkeys, which are considered to play an important role in the LC, were classified into 5 groups on the basis of morphological patterns of the GA. Many neurons of both species of monkeys were positive for the XDH test while some neurons of the crab-eating monkey as well as a few neurons of the Rhesus monkey were positive for the GLO reaction. The LC of both species of monkeys must be composed of metabolically one kind of identical medium-sized parasympathetic neurons whose GA may continously undergo 5 distinct phasic changes depending on the functional state of that cell. However, the GA changes its shape much more significantly even within each group of the 5 in the crab-eating monkey than in the Rhesus monkey. The GA Type IV may correspond to the catabolic phase of the GA during which biosynthesis of both catecholamines and vitamin C should be going on. Production of vitamin C may greatly help biosynthesis of catecholamines in LC. The difference in species is evident between the 2 kinds of monkeys studied in regard to the degree of their ability to synthesize these substances. The degree of the ability to synthesize vitamin C parallels the density distribution of Type IV neurons in LC whose GA often develops much more greatly in the crab-eating monkey than in the Rhesus monkey.

Alcohol Oxidoreductases↗
PubMed1978

Organochlorines in fish and crabs from the Kristiansand fjord in Norway.

The levels of sum-DDT, PCBs, and HCB in fish liver and crab hepatopancreas from the Kristiansand fjord area in Norway have been determined (fig. 1). The respective mean levels (fat weight basis) in stationary fish species and crabs are given in table I. The levels of PCBs and sum-DDT were about the same, and the HCB level two to one hundred times higher than corresponding levels reported for codfish (liver) from several harbours along the Norwegian coasts (Brevik et al. in press). The levels calculated on a wet weight basis, found is stationary fish from the harbour of Kristiansand and Topdals-fjord were two to three times higher than those in crabs. Calculated on a fat weight basis, however, the levels in stationary fish and crabs were much more similar (table II). The harbour area was more contaminated with PCBs and HCB than the other sites examined. It seems impossible, however, on the basis of present data to further pinpoint sources of the relatively high degree of HCB contamination in the Kristiansand fjord area.

Animals↗
PubMed1978

Dominance and effects of strange conspecifics on aggressive interactions in the hermit crab Pagurus longicarpus (say).

Dominance orders in the hermit crab Pagurus longicarpus were observed in the laboratory. Groups of four crabs formed loose dominance hierarchies as determined by repeated display and retreat behaviour. Stronger dominance orders were inversely correlated with the frequency of aggressive interactions. Recognition of individuals, as measured by frequency and intensity of aggressive encounters between familiar crabs and introduced strangers, was not important in maintaining dominance orders. Rather, P. longicarpus recognized the aggressive state of conspecifics, as shown by frequencies of aggressive encounters after individuals of different dominance rankings were exchanged between established hierarchies.

Aggression↗
PubMed1979

Respiration and heart rate in exercising land crabs.

Land Crabs, Cardisoma guanhumi, were fitted with respiratory masks and E.C.G. electrodes and run for 10 or 20 min on a treadmill at speeds of 150 and 300 cm/min. Aerobic metabolism increased linearly with the speed of locomotion. The recovery period was characterized by a large oxygen debt. The primary respiratory adjustment to exercise was an increased ventilation volume; only a minor increase in oxygen extraction occurred. The respiratory exchange ratio increased during exercise and during recovery, presumably correlated with a metabolic acidosis. These results are similar to data collected for exercising vertebrates and the net cost of locomotion of crabs appears similar to quadrupeds. However, the heart rate in exercising crabs changed in an unexpected way: during moderate exercise no change was noted, but during heavy exercise a bradycardia developed. The reduction in rate resulted from an increase in interbeat interval and frequent pauses in the heart beat.

Animals↗
PubMed1975

Glyceraldehyde-3-phosphate dehydrogenase of horseshoe crab (Tachypleus tridentatus).

Glyceraldehyde-3-phosphate dehydrogenase [ED 1.2.1.12] was purified from the horseshoe crab, a living fossil, and its properties were examined. 1 The purified enzyme was homogeneous as judged by various tests. The enzyme, like enzymes from other sources, was a tetramer with a subunit molecular weight of 36,000. The kinetic parameters and pH optimum were also similar to those of other enzymes, though the enzyme was more stable against heat and pH denaturations. 2 Analysis of SH groups showed that there were 4 SH groups per subunit, one of which was essential for the enzyme activity and was highly reactive. 3. CD spectra of the enzyme suggested that the enzyme had a very high content of beta-structure (ca. 45 per cent). 4. The horseshoe crab enzyme could form a hybrid in vitro with the rabbit muscle enzymes in concentrated salt solution at acidic pH. 5. There results indicate that the enzyme has overall structural similarity to other enzymes and that the enzyme is highly conserved during a long period of evolution. Some discussions on the structure and activity of the horseshoe crab enzyme are made in comparison with the enzymes from other sources.

Amino Acids↗
PubMedDate not supplied

[Adenosine triphosphatase activity in the organs of the crab Hemigrapsus sanguineus, acclimated to sea water of different salinity].

In crabs acclimated to low salinity, the activity of Na, K-ATPase from the gills increases; the activity also increases in the antennal glands after acclimation of the animals to high salinity. The activity of Na, K-ATPase in the abdominal ganglion and in the heart does not depend on the salinity to which crabs had been acclimated. Changes in the activity of Mg-ATPase in the gills and antennal glands associated with acclimation of crabs to sea water with different salinity correspond to those in the activity of Na, K-ATPase.

Adaptation, Physiological↗
PubMed1979

Coagulation in the sand crab (Ovalipes bipustulatus).

The coagulation mechanism of the sand crab (O. bipustulatus) has been investigated. From the coagulocytes (amoebocytes) present in the crab haemolymph (blood), fibrinogen (coagulogen) was isolated. It was shown to be homogeneous by electrophoresis on S.D.S. polyacrylamide gel and had a molecular weight similar to the A alpha-chain of human fibrinogen. Unlike human fibrinogen. Unlike human fibrinogen it cannot be dissociated by reduction. In fibrin polymerization, a crosslinking process takes place and this process was inhibited by glycine ethyl ester. A fibrin stabilizing factor is present in the crab haemolymph and this protein was able to cross-link human fibrin in the same manner as human factor XIII.

Animals↗
PubMed1976

[Protein composition of hemolymph from the crabs Carcinus mediterraneus Czerniavsky, healthy or parasitized by Sacculina carcini Thompson].

The proteic composition of haemolymph from C. mediterraneus varies during the intermoult cycle. Some proteic fractions are occasionally absent in post-ecdysis. At each intermoult stage, parasitized Crabs have generally the same protein pattern as healthy ones, but the presence of the observed fractions is not constant. Compared healthy Crabs, the sacculinized animals show a surnumerary proteic fraction. With very short delay, the injection of ecdysterone puts the proteic composition of haemolymph from sacculinized Crabs in order, this composition becomes comparable to that from healthy individuals.

Animals↗
PubMed2026

Lipid metabolism in hepatopancreas and ovaries of the mud crab Scylla paramamosain during vitellogenesis.

Ovarian lipids are essential nutrients that fundamentally determine oocyte and offspring quality, and ultimately affect the reproductive performance of decapod crustaceans. Lipids accumulated in the ovaries during vitellogenesis are mainly derived from the hepatopancreas. However, the molecular mechanisms underlying lipid metabolism in the hepatopancreas and ovaries during vitellogenesis remain largely unclear. In this study, comparative transcriptomic and lipidomic analyses were conducted on the hepatopancreas and ovaries of the mud crab Scylla paramamosain. From early to late vitellogenic stages, 454 lipid species were significantly increased and 17 decreased in abundance in the hepatopancreas, and 609 increased and 23 decreased in abundance in the ovaries. Meanwhile, there were 1481 upregulated and 963 downregulated transcripts in the hepatopancreas, and 3402 upregulated and 1478 downregulated transcripts in the ovaries. Subsequently, KEGG pathway co-enrichment analysis showed that the de novo biosynthesis of glycerophospholipids and glycerolipids was enhanced in the hepatopancreas, with upregulated ALDH, GPAT, plsC, PLPP, FASN, and HSD17B8 transcripts and elevated abundances of PC, PE, PS, PA, PG, DG, and TG species from the early to late vitellogenic stages in mud crabs. In contrast, glycerophospholipid catabolism and conversion were activated in the ovaries, with upregulated PLA2G, LYPLA1, NTE, GPCPD1, PLD_1, PGS1, and CRLS transcripts and elevated abundances of LPC, LPE, LPS species. These findings provide novel insights into the molecular mechanisms of lipid metabolism during vitellogenesis in decapod crustaceans.

Animals↗
PubMed1975

Isolation and studies of the granules of the amebocytes of Limulus polyphemus, the horseshoe crab.

Granules were isolated from the cytoplasm of the amebocytes of Limulus polyphemus, the horseshoe crab, by disruption of cells obtained from blood which had been drawn into 2 mM propranolol. The granules subsequently were purified by centrifugation through a sucrose gradient that contained heparin. Extracts of the granules were prepared by freezing and thawing the granule preparations in distilled water. Transmission and scanning electron microscopy of the granules revealed round or ovoid particles. However, only one type of granule appeared to be present. The ultraviolet spectrum of the extract of amebocyte granules demonstrated a peak at 277 nm at pH 7.4, and a shift into two peaks of 281 nm and 290 nm at alkaline pH. Analytical ultracentrifugation revealed a pattern similar to that observed with lysates prepared from intact amebocytes. Polyacrylamide gel electrophoresis, in the presence of urea at pH 4.5, demonstrated patterns similar to those observed with amebocyte lysate. Extracts of the granules were gelled by bacterial endotoxin. The blood of the horseshoe crab contains only one type of cell, the amebocyte. Previous studies have shown that the blood coagulation mechanism of Limulus is contained entirely within amebocytes. The current studies suggest that the granules, which pack the cytoplasm of these cells, contain all of the factors required for the coagulation of blood, including the clottable protein. The intracellularly localized coagulation system is released from amebocytes when their granules rupture during cell aggregation.

Animals↗
PubMed1975

The function of hemocyanin in respiration of the blue crab Callinectes sapidus.

Blood PO2 in the blue crab Callinectes sapidus, a very active species of tropical origin, is lower at 22 degrees C than that of larger crabs in colder waters. These low oxygen levels permit its hemocyanin to be highly oxygenated at the gill, and to deliver almost half of its oxygen to the tissues in resting animals. Sustained muscular activity results in conspicuous decreases in blood PO2, pH and hemocyanin oxygenation. Although the venous reserve is fully utilized, hemocyanin oxygenation at the gill decreases so much that there is no change in its total quantitative function. The large Bohr shift becomes functional during activity, but its quantitative importance is not clear.

Animals↗
PubMed1977

The retina-lamina projection in the crab Leptograpsus variegatus.

In the crab, Leptograpsus variegatus, the projection of retinula cell axons to the lamina was investigated by tracing them through a series of semi-thin sections. Forty-four such axons were traced from a single group of ommatidia as far as the distal layers of the lamina. The eight receptor axons of one ommatidium project to a single lamina cartridge. Therefore, because the crab has a fused rhabdom, angular information is conserved in vision, and the outside world is projected literally onto the lamina, just as it is in the standard non-dipteran pattern of insects. The belief of previous workers that other decapod eyes show neural superposition was an inference based primarily on the patterns of penetration of the basement membrane by receptor axons, and on degeneration experiments. This evidence is reviewed, shown to be inadequate and discussed in the light of the projection now demonstrated for Leptograpsus.

Animals↗