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Biosorption of copper(II) and cobalt(II) from aqueous solutions by crab shell particles.

Biosorption of each of the heavy metals, copper(II) and cobalt(II) by crab shell was investigated in this study. The biosorption capacities of crab shell for copper and cobalt were studied at different particle sizes (0.456-1.117 mm), biosorbent dosages (1-10 g/l), initial metal concentrations (500-2000 mg/l) and solution pH values (3.5-6) in batch mode. At optimum particle size (0.767 mm), biosorbent dosage (5 g/l) and initial solution pH (pH 6); crab shell recorded maximum copper and cobalt uptakes of 243.9 and 322.6 mg/g, respectively, according to Langmuir model. The kinetic data obtained at different initial metal concentrations indicated that biosorption rate was fast and most of the process was completed within 2h, followed by slow attainment of equilibrium. Pseudo-second order model fitted the data well with very high correlation coefficients (>0.998). The presence of light and heavy metal ions influenced the copper and cobalt uptake potential of crab shell. Among several eluting agents, EDTA (pH 3.5, in HCl) performed well and also caused low biosorbent damage. The biosorbent was successfully regenerated and reused for five cycles.

Absorption↗

Possible role of carbonic anhydrase, V-H(+)-ATPase, and Cl(-)/HCO3- exchanger in electrogenic ion transport across the gills of the euryhaline crab Chasmagnathus granulatus.

We studied the participation of carbonic anhydrase (CA), V-H(+)-ATPase, and Cl(-)/HCO3- exchanger in electrogenic ion absorption through the gills of Chasmagnathus granulatus. CA activity was measured in anterior gills and posterior gills after acclimation to 2 per thousand, 10 per thousand, 30 per thousand (about seawater), and 45 per thousand salinity. The highest CA specific activity was detected in the microsomal fraction in anterior gills, and in the cytosolic fraction, in posterior ones. Both fractions were strongly induced by decreasing salinity only in posterior gills. Perfusion of posterior gills from crabs acclimated to either 2 per thousand or 10 per thousand with acetazolamide inhibited CA activity almost completely. In posterior gills from crabs acclimated to 2 per thousand and perfused with 20 per thousand saline (iso-osmotic for these crabs), acetazolamide reduced transepithelial potential difference (V(te)) by 47%, further addition of ouabain enhanced the effect to 88%. Acetazolamide had no effect in the same gills perfused with 30 per thousand saline (iso-osmotic for seawater acclimated crabs). Bafilomycin A1 and SITS (inhibitors of V-H(+)-ATPase and Cl(-)/HCO3-) reduced V(te) by 15-16% in gills perfused with normal 20 per thousand saline, and by 77% and 45%, respectively when they were applied in Na-free 20 per thousand saline, suggesting the participation of those transporters and cytosolic CA in electrogenic ion absorption.

Acetazolamide↗

The effects of hypoxia and pH on phenoloxidase activity in the Atlantic blue crab, Callinectes sapidus.

In its natural coastal and estuarine environments, the blue crab, Callinectes sapidus, often encounters hypoxia, accompanied by hypercapnia (increased CO2) and an associated decrease in water pH. Previous studies have shown that exposure to hypercapnic hypoxia (HH) impairs the crab's ability to remove culturable bacteria from its hemolymph. In the present study we demonstrate that the activity of phenoloxidase (PO), an enzyme critical to antibacterial immune defense in crustaceans, is decreased at the low levels of hemolymph O2 and pH that occur in the tissues of blue crabs exposed to HH. Hemocyte PO activity was measured at tissue O2 levels that occur in normoxic (5% and 15% O2, approximate venous and arterial hemolymph, respectively) and hypoxic (1% O2) crabs and compared to PO activity in air-saturated conditions (21% O2). PO activity decreased by 33%, 49% and 70% of activity in air at 15%, 5% and 1% O2, respectively. When O2 was held at 21% and pH lowered within physiological limits, PO activity decreased with pH, showing a 16% reduction at pH 7.0 as compared with a normoxic pH of 7.8. These results suggest that decreased PO activity at low tissue O2 and pH compromises the ability of crustaceans in HH to defend themselves against microbial pathogens.

Animals↗

Molecular characterization and expression analysis of vitellogenin in the marine crab Portunus trituberculatus.

As a precursor of the major yolk protein vitellin (Vn), vitellogenin (Vg) has been studied in crustacean for decades, mainly in shrimp. However, little is known about the Vg molecule in crabs. In the present study, we report a cDNA encoding Vg in the marine crab Portunus trituberculatus, an important commercial species in aquaculture. The cDNA sequence is 7,846 bp in length, containing a 7,680 bp open reading frame, that encodes 2,560 amino acid residues. The deduced amino acid sequence showed 32-75% identity with other known crustacean Vgs. Seven potential cleavage sites (RXXR) were identified in the deduced Vg precursor. SDS-PAGE and Western blotting analysis demonstrated that Vns in the ovary of the mature crab consisted of three major polypeptides (102, 100 and 85 kDa). Northern blotting analysis revealed that Vg was mainly expressed in hepatopancreas in vitellogensis females. A Vg transcript was also identified in the ovary of the crab by reverse transcription-polymerase chain reaction analysis.

Amino Acid Sequence↗

Effect of aerial exposure on the antioxidant status in the subantarctic stone crab Paralomis granulosa (Decapoda: Anomura).

In Tierra del Fuego (Southern South America), the stone or false king crab, Paralomis granulosa represents one of the most important crab fisheries. After capture, animals are kept in baskets and exposed to dryness for several hours, when the water flow through the gills is interrupted. As a consequence a concomitant increase of reactive oxygen species begins, triggering oxidative stress. The aim of this study was to determine oxidative stress and antioxidant enzyme activities due to air exposure in different tissues of P. granulosa. Fifty crabs (carapace length >82 mm) were captured in Beagle Channel (54 degrees 50'S, 68 degrees 20'W) during winter 2004. Five groups of 10 crabs each were exposed to dryness at 6 degrees C for 0, 3, 6, 12 or 24 h, respectively. Activity of superoxide dismutase (SOD), catalase (CAT), glutathione S transferase (GST) protein and lipid oxidation were measured in gills, muscle, hepatopancreas and haemolymph samples. Almost all analyzed tissues showed antioxidant enzymes activity, which varied with time of air exposure. The maximum enzyme activity was measured after 6 h of air exposure. Protein oxidation levels varied significantly in gills. Lipid peroxidation levels increased significantly in muscle and hepatopancreas. The critical time of air exposure probably occurs at 6 h. Thereafter animals were unable to induce the synthesis of antioxidant enzymes or proteins. This should be taken into account to minimize the stress generated by the commercial capture process.

Air↗

Changes in oxygen consumption and respiratory enzymes as stress indicators in an estuarine edible crab Scylla serrata exposed to naphthalene.

The sublethal effect of naphthalene was studied on the physiology of a mud crab Scylla serrata. The 96 h acute toxicity of naphthalene was determined and found to be 28 mg 1(-1) (LC100), 18 mg 1(-1) (LC50), 10 mg 1(-1) (LC0) respectively. The 30 days sublethal effect (LC0) 9 mg 1(-1), 8 mg 1(-1), 10 mg 1(-1), of naphthalene was investigated in the crab S. serrata with reference to oxygen consumption and changes in the activity of respiratory enzymes. The results indicated that naphthalene caused disturbance in the normal physiology of the crab. The bioaccumulation of naphthalene was also investigated in gills, hepatopancreas, haemolymph and ovary. The consumption of oxygen increased in the naphthalene medium when compared with that of the crabs exposed to naphthalene free medium. A decreased trend in the activity of respiratory enzymes such as lactate dehydrogenase (LDH), isocitrate dehydrogenase (ICDH), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), alpha-ketoglutarate dehydrogenase (alpha-KDH) and glutathione (GSH) were recorded in the hepatopancreas, ovary and gills of S. serrata for all the tested concentrations of naphthalene and the results were analyzed for their significance.

Animals↗

Cloning and characterisation of a prophenoloxidase from the haemocytes of mud crab Scylla serrata.

A prophenoloxidase (proPO) cDNA was cloned from the haemocytes of mud crab Scylla serrata using oligonucleotide primers and RT-PCR. Both 3'- and 5'-regions were isolated by rapid amplification of cDNA end (RACE) method. Analysis of the nucleotide sequence revealed that the cDNA clone has a full length of 2663bp, with an open reading frame of 2019bp, a 124-bp 5'-untranslated region, and a 520-bp 3'-untranslated region containing a poly A signal. It encodes a protein of 673 amino acids with a predicted molecular weight of 77.5kDa and with an estimated pI of 5.96. It contains two putative tyrosinase copper-binding motifs with six histidine residues (copper A, 185, 189, 211, and copper B, 346, 350, 386). The proPO has thiol-ester-like motif (GCGWPQHM), which showed similar structural features of proPOs from other decapod crustaceans. It also contains five possible glycosylation sites, and a conserved C-terminal region common to all known proPOs. Sequence comparison showed that the proPO-deduced amino acid of mud crab S. serrata has an overall similarity of 78%, 57%, 56%, 51-55%, 54%, 53%, 52%, 52%, and 52% to that of Dungeness crab Cancer magister, American lobster Homarus americanus, European lobster Homarus gammarus, kuruma prawn Marsupenaeus japonicus, crayfish Pacifastacus leniusculus, white shrimp Litopenaeus vannamei, tiger shrimp Penaeus monodon, green tiger shrimp Penaeus semisulcatus, and giant freshwater prawn Macrobrachium rosenbergii, respectively. The proPO was strongly expressed in haemocytes, but not in heart, eyestalk, gill, muscle, ovary, hepatopancreas, stomach, and intestine. The proPO transcript of mud crab S. serrata increased significantly in 12 and 24h post-lipopolysaccharide (LPS) injection, but returned to the original values in 72h post injection.

Animals↗

Acute toxicities of four metals on the early life stages of the crab Chasmagnathus granulata from Bahía Blanca estuary, Argentina.

Acute semistatic toxicity tests were carried out for 96 h with first zoeae and young crabs of Chasmagnathus granulata. Survival curves and LC50 (lethal concentration 50, the concentration which produces the death of 50% of the exposed population) indices for copper, zinc, cadmium, and lead were determined. Furthermore, mixture toxicity tests (Cd/Cu and Cd/Zn) with first-stage larvae were also carried out. The LC50-96 h values determined in this study were 1093.4 (881-1319) microg Pb2+ L(-1), 219.2 (188.9-248.9) microg Cu2+ L(-1), 172.1 (141.3-203.6) microg Zn2+ L(-1), and 47.8 (37.9-58.0) microg Cd2+ L(-1) for zoeae I and 130.1 (121.7-139.0) mg Cu2+ L(-1), 51.0 (41.9-61.6) mg Zn2+ L(-1), and 35.7 (30.1-41.9) mg Cd2+ L(-1) for young crabs. The LC50-96 h indices for mixture tests with zoeae I were 260.6 (227.3-286.3) microg Cd2+/Zn2+ L(-1) and 41.3 (37.4-60.7) microg Cd2+/Cu2+ L(-1). Cadmium presented the highest acute toxicity for both stages of the life cycle examined. The toxicity of the metals analyzed followed the order cadmium >zinc>copper>lead. First zoeae were more sensitive than young crabs to acute exposure to all metals analyzed. The young crabs were considered potentially dangerous agents of transference to the associated trophic chain because of their relatively elevated resistance and their capacity to bioaccumulate heavy metals in their tissues. Mixed toxicity tests carried out on first-stage larvae showed different kinds of interactions. Cadmium/copper presented an additive interaction trend while the mixture cadmium/zinc showed an antagonistic interaction.

Aging↗

Interactive cellular and physiological responses of the freshwater crab Potamonautes warreni to cadmium and microbial gill infestations.

Cellular and physiological responses of the freshwater crab, Potamonautes warreni, to cadmium and microbial gill infestations were investigated. Infested crabs were collected from the Mooi River, at Noordbrug, Northwest Province, South Africa in the autumn of 1995 and exposed to 0.2mg Cd(2+)L(-1) or kept unexposed under constant laboratory conditions for 7, 14 and 21 days at 24 degrees C. Cellular lesions with microbial gill infestations were persistent over 21 days and showed a similar species diversity and density as recorded in the previous summer [Schuwerack et al., 2001a. Pathological and physiological changes in the South African freshwater crab, P. warreni Calman induced by microbial gill infestations. J. Invertebrate Pathol. 77(4), 259-269]. With Cd exposure the microbial community disappeared and crabs showed a higher mean but wider range in ammonia excretion and lower mean O:N ratio after 7 days. After 14 days exposure to Cd, time- and stressor-specific cellular and physiological responses included degeneration of oxygen and gas exchange gill tissues and a mean reduced growth rate, ion exchange, a significantly reduced O:N ratio (P<or=0.05) and induced hemolymph pH (P<or=0.05). Both stressors, i.e. gill infestation and Cd, produce a barrier, which obstructs pathways in ion exchange and oxygen uptake, resulting in NH(3)/NH(4)(+) retention and similar physiological responses after 21 days. The interactive cellular and physiological mechanisms in P. warreni exposed to multiple stress are discussed.

Adaptation, Physiological↗

Crab shell-based biosorption technology for the treatment of nickel-bearing electroplating industrial effluents.

This paper discusses the possible application of a biosorption system with acid-washed crab shells in a packed bed up-flow column for the removal of nickel from electroplating industrial effluents. Between two nickel-bearing effluents, effluent-1 is characterized by considerable amount of light metals along with trace amounts of lead and copper. Effluent-2 is characterized by relatively low conductivity, total dissolved solids and total hardness compared to effluent-1. Crab shells exhibited uptakes of 15.08 and 20.04 mg Ni/g from effluent-1 and effluent-2, respectively. The crab shell bed was regenerated using 0.01 M EDTA (pH 9.8, aq. NH3) and reused for seven sorption-desorption cycles. The EDTA elution provided elution efficiencies up to 99% in all the seven cycles. This, together with the data from regeneration efficiencies for seven cycles, provided evidence that the reusability of crab shell in the treatment of nickel-bearing electroplating industrial effluents is viable.

Adsorption↗

Removal of nickel from aqueous solutions using crab shells.

Partially converted crab shell waste, which contains chitosan, was used to remove nickel from water. The chelating ability of chitosan makes it an excellent adsorbent for removing pollutants. Advantages of chitosan in crab shells include availability, low cost, and high biocompatibility. The metal uptake by partially converted crab shell waste was successful and rapid. The sorption occurred primarily within 5 min. The sorption mechanism appears to be quite complicated and cannot be adequately described by either the Langmuir or Freundlich theories. Various anions, including chloride, bromide, fluoride, acetate, sulfate, nitrate, and phosphate, were found to have a very small effect on the capacity of the crab shells for uptake of nickel. The effect of pH was also found not to be prominent.

Adsorption↗

Crabs, leeches and trypanosomes: an unholy trinity?

The red king crab Paralithodes camtschaticus was deliberately introduced to the Barents Sea in the 1960s and 1970s from its native area in the North Pacific. The carapace of these crabs is a favoured substrate for the leech Johanssonia arctica to deposit its eggs, and the leech is a vector for a trypanosome blood parasite of marine fish, including cod. We examined cod for trypanosome infections during annual cruises along the coast of Finnmark in North Norway over three successive years from stations along a gradient of over 1000 km. In every year the level of trypanosome infection in cod was significantly highest in the area with the greatest density of king crabs. We propose the hypothesis that the burgeoning population of red king crabs in this area is indirectly responsible for increased transmission of trypanosomes to cod by promoting an increase in the population of the leech vector.

Animals↗

Seasonal fluctuations of tissue mercury contents in the European shore crab Carcinus maenas from low and high contamination areas (Ria de Aveiro, Portugal).

The main objective was to study the seasonal variation of mercury concentrations in different tissues (muscle, hepatopancreas and gills) of Carcinus maenas from low and high Hg contaminated areas, a valuable resource in temperate estuaries and a possible pathway for human uptake. Individuals of two size classes (around 35 and 55 mm cephalothorax wide) were captured monthly between March 1999 and May 2000 in two areas of Ria de Aveiro: in the main navigation channel that connects the lagoon to the sea, and in the inner lagoon area heavily contaminated by mercury (maximum Hg in sediments of 5.4 microg g(-1)). Pronounced decreases in salinity and temperature and reduced food availability in winter seemed to be the responsible for the decline of the crab condition index (0.75-0.45) in larger individuals. Muscle and hepatopancreas exhibited higher mercury concentrations than gills, with concentrations in the contaminated site ranging from 0.03 to 0.63 microg g(-1) and 0.02 to 0.34 microg g(-1), respectively. Linear regressions between muscle and hepatopancreas (r=0.94, p<0.001) and muscle and gills (r=0.97, p<0.001) suggested a rapid redistribution of mercury inside the organism. During winter, a rapid elimination of mercury was found in the three analysed tissues followed by uptake. Larger crabs presented elimination rates from 18 to 34 ng g(-1) per week, while the smaller crabs showed lower elimination rates (10-24 ng g(-1) per week). The uptake was similar in both size classes (11-15 ng g(-1) and 8.1-15 ng g(-1) per week, respectively for large and small crabs). Our results suggest that C. maenas harvested in the contaminated areas must be considered with caution, since Hg concentrations were found to exceed the threshold concentration allowed for human consumption (0.5 microg g(-1)).

Animals↗

Aggressiveness and memory: subordinate crabs present higher memory ability than dominants after an agonistic experience.

A relationship between aggressiveness and memory has been proposed in several studies with different animal species. Here, we study this possibility in the crab Chasmagnathus granulatus, using the context-signal memory model (CSM) that involves an association between the learning context and a visual danger stimulus. Each experiment consisted of an agonistic phase and a memory one. During the former, matched pairs of male crabs were staged in two 10-min encounters and the dominant or subordinate condition of each member of the dyad was determined. During the memory phase, crabs were trained to acquire CSM and tested 24 h later. Results showed that the agonistic encounter, staged 48 h before the acquisition of CSM, can modulate memory according to the dominance condition of the fighter; in such a way that memory retention of subordinates results higher than that of dominants. By contrast, when the memory phase preceded the agonist one, forthcoming dominants and subordinates did not differ in their memory ability. The memory modulation would not be linked to a dominance status but to a persistent dominance relationship fully reconstructed in each encounter between the same opponents. Therefore, the crab's CSM would not depend directly on predetermined intrinsic properties, but on the outcome of the fight, which would be determined in turn by the relative aggressiveness of the fighters. The finding that the agonistic episode modulates memory opens the possibility of using this episodic interference to probe the function of diverse phases of CSM.

Aggression↗

Toxicity of hexachlorobenzene and its transference from microalgae (Chlorella kessleri) to crabs (Chasmagnathus granulatus).

The aim of this work was to study the transference of hexachlorobenzene from a green alga (Chlorella kessleri) to an estuary crab (Chasmagnathus granulatus), and to analyze the toxic effects that the xenobiotic has on the latter. The effect of hexachlorobenzene uptake was evaluated measuring oxidative stress, Uroporphyrinogen decarboxylase activity and morphometric parameter alteration, and also performing a histological analysis of crab hepatopancreas. Results demonstrated that hexachlorobenzene enters the alga, is accumulated in it, and then transferred into the crab, causing a decrease in Uroporphyrinogen decarboxylase activity in both organisms. The high malondialdehyde levels detected in crab hepatopancreas after the toxic treatment suggested the existence of hexachlorobenzene-induced lipid peroxidation. Antioxidant defenses such as superoxide dismutase activity and reduced glutathione content fell below normal values on the fourth week of treatment. At the same time, the hepatosomatic index, used as a morphometric parameter, reduced 20% with respect to the control. The histological analysis revealed epithelium disorganization in hepatopancreas tubules, confirming the existence of structural damage caused by hexachlorobenzene.

Animals↗

The synthesis and effects of prostaglandins on the ovary of the crab Oziotelphusa senex senex.

The possible involvement of prostaglandins in the regulation of ovarian development in the crab Oziotelphusa senex senex was investigated. Uptake of labelled arachidonic acid into the ovary of the crab was significantly greater than the other tissues. Prostaglandin H synthase activity was significantly increased in the ovary during the late vitellogenic stage when compared to immature ovary. The biosynthesis of different prostaglandins in the ovary was also measured during the crab reproductive cycle. Injection of prostaglandin F(2alpha) and prostaglandin E(2) significantly increased ovarian index and oocyte diameter in a dose-dependent manner. In contrast, injection of prostaglandin D(2) did not affect ovarian growth. These results demonstrate the presence of prostaglandin biosynthetic system in ovary of the fresh water crabs.

Animals↗

Continuous neurogenesis in the olfactory brain of adult shore crabs, Carcinus maenas.

To scrutinize the common belief that the number of neurons in the CNS of adult decapod crustaceans stays constant, in spite of their dramatic postlarval increase in size, I counted olfactory projection neurons (OPNs) in the brains of differently-sized postlarval shore crabs, Carcinus maenas, and performed in vivo labeling of proliferating cells with 5-bromo-2'-deoxyuridine (BrdU) on brains of adults. The number of OPNs increases continuously throughout the postlarval life of shore crabs and approximately doubles from the very young to the oldest animals. Brain sections from adult crabs labeled with BrdU revealed ongoing proliferation of cells in the lateral soma cluster, which consists of OPN cell bodies, and in the cluster of somata of hemiellipsoid body local interneurons, which are the targets of the OPNs. Post-injection survival times from 5.5 to 120 h revealed a small but relatively constant number of labeled nuclei with neuronal morphology in both soma clusters of all specimens (31.3 +/- 9.5 S.D. nuclei per lateral cluster, n = 29; 20.1 +/- 4.5 S.D. nuclei per hemiellipsoid body cluster, n = 10). The labeled nuclei were located in a distinct proliferative zone in each cluster. There were significantly more labeled nuclei in both soma clusters after a prolonged post-injection survival time of 1 month (71.3 +/- 7.8 S.D. nuclei per lateral cluster, n = 4; 38.2 +/- 7.1 nuclei per hemiellipsoid body cluster, n = 6). In both soma clusters the labeled nuclei formed a compact group that was dislocated from the proliferation zone towards the outer edge of the cluster. In the proliferation zone of the lateral cluster histological stainings revealed cell bodies of typical neuronal shape that are slightly smaller and more intensely stained than the surrounding OPN somata. Some of these cell bodies were captured in various stages of mitosis. Collectively, these data indicate that continuous neurogenesis occurs in the central olfactory pathway of the brain of shore crabs throughout their entire adult life. This unexpected structural plasticity may enable long-lived decapod crustaceans to adapt to ever-changing olfactory environments.

Age Factors↗

Changes in metallothionein concentrations in response to variation in natural factors (salinity, sex, weight) and metal contamination in crabs from a metal-rich estuary.

Intermoult male and female crabs Pachygrapsus marmoratus and Carcinus maenas were sampled from three sites between the mouth and 25 km upstream in the Gironde, the most Cd-contaminated estuary in France, in order to study the relative importance of natural factors (salinity, sex, weight) and accumulated metal concentrations on metallothionein (MT) concentrations. In the two species studied, higher metal, total protein and MT concentrations were observed in the hepatopancreas than in the gills. In P. marmoratus, MT concentrations were mainly related to changes in the natural factors even if MT and Zn concentrations were positively correlated in the hepatopancreas whereas in C. maenas, the main relationships were with accumulated metal levels. In the case of the natural factors, the most important ones were weight in gills of both crab species, and salinity changes in both hepatopancreas and gills of P. marmoratus. Cd and Cu concentrations in both organs of the two species were inversely related to salinity. The same observation was found for Zn concentrations in C. maenas but not in P. marmoratus. In the hepatopancreas of both species, the highest total protein concentrations were found in crabs from the site with the highest salinity, whereas there were no such differences in the gills. It seems that changes in MT concentrations are linked more to changes in general protein metabolism than to changes in metal accumulation. Thus it was important to examine the storage of metals in other tissue compartments, particularly the insoluble fraction which includes mineral granules which is known to also contribute to trace metal detoxification in invertebrates. In the gills of the crabs, Zn was present mainly in the insoluble fraction, whereas Cd was nearly equally distributed between soluble and insoluble fractions. In contrast, Cu in the gills and all three metals in the hepatopancreas of both species were mainly cytosolic, but this does not necessarily imply a predominant role for MT since the cytosolic fraction also includes other macromolecules which may be the target binding site for accumulated trace metals.

Journal Article↗