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At least 19 recordsLinked to original sources
PubMed2005

Biochemical and physiological responses after exposure to microcystins in the crab Chasmagnathus granulatus (Decapoda, Brachyura).

Microcystins are usually the predominant cyanotoxins present in both drinking and recreational waters after cyanobacterial blooms. Their classic toxic effect is hepatotoxicity through inhibition of serine/threonine phosphatases. However, recent studies also reported oxidative stress generation and disruption of ion regulation in aquatic organisms after microcystins exposure. In the present study, aqueous extracts of Microcystis aeruginosa were administered to the estuarine crab Chasmagnathus granulatus (Decapoda, Brachyura) by gavage in variable doses (from 34 to 860 microg kg(-1)) and exposure times (6, 12, and 72 h). A control group was exposed to saline solution. Analyzed variables included oxygen consumption, lipid peroxidation (LPO), enzyme activities (glutathione S-transferases or GST; alanine aminotransferase or ALT; aspartate aminotransferase or AST; and lactate dehydrogenase or LDH), glycogen, and microcystins content. Oxygen consumption increased in organisms exposed for 12h to 860 microg kg(-1) of microcystins and a similar result was observed after 72 h at doses equal to or higher than 34 microg kg(-1). LPO levels increased in doses equal to or higher than 34 microg kg(-1) after 72 h. GST and LDH activities increased after 12 h (at a dose of 860 microg kg(-1)), but ALT and AST activities remained unaltered in all experimental conditions. Glycogen content decreased after 72 h exposure at doses equal to or higher than 172 microg kg(-1). After 12h of exposure to 860 microg kg(-1) of microcystins, the concentration found in the hepatopancreas of C. granulatus was 13.17+/-0.56 microg kg(-1). In crabs exposed to doses higher than 172 microg kg(-1) during 72 h this value raised to 32.14+/-4.12 microg kg(-1). The obtained results indicated that microcystins exposure led the tissue to an oxidative stress condition (high LPO levels), at least in part favored by the augment of oxygen consumption, altering the glycogen metabolism. GST responses were only observed in the short-term experiment (12 h) and no effect on classical markers of vertebrate liver damage (ALT and AST) was observed. Although the hepatopancreas from C. granulatus accumulated a relatively low concentration of toxins, it was enough to induce physiological and biochemical disturbances.

Animals↗
PubMed2005

The mitochondrial genome of the Japanese freshwater crab, Geothelphusa dehaani (Crustacea: Brachyura): evidence for its evolution via gene duplication.

The translocation of tRNA genes has occurred frequently among multiple independent arthropod lineages. However, the mechanisms of such gene rearrangement are still unclear. In this study we sequenced the nearly complete mitochondrial genome of the Japanese freshwater crab, Geothelphusa dehaani (Decapoda, Brachyura, Potamidae). Its size is relatively large (app. 24 kb) for higher animal mtDNA and is due to the presence of many intergenic noncoding sequences (IGNs), one of which is a large repeat region (>7.0 kb). Excluding the repeat region and the putative control region (514 bp), the total size of IGNs (1953 bp) is still the largest reported in arthropods. In comparison to the proposed ancestral arrangement for the insect-crustacean clade, G. dehaani displays changes in the positional order for three tRNA genes (trnQ, trnL(uur) and trnH). At the putative former and current locations for trnQ and trnH, there are IGNs with high similarities to corresponding sequences in the ancestral arrangement. This suggests the occurrence of partial duplication, followed by a loss of function for one copy of these two duplicated genes in G. dehaani. Furthermore, three trnLs (one trnL(uur) and two trnL(cun)s) are found in G. dehaani; their sequences are highly similar to each other (70.8-82.5%) and similar to the trnL(cun) of other arthropods. This suggests that duplication of trnL(cun) occurred at least twice, and the current trnL(uur) of G. dehaani arose by a subsequent anticodon alternation. These observations provide direct evidence for the "duplication-random loss" model for mtDNA gene rearrangement. Comparisons with other available Brachyuran data(http://www.ncbi.nlm.nih.gov/genomes/ORGANELLES/6657.html) suggest that two of the three tRNA translocations are unique in G. dehaani. For G. dehaani, where duplications have occurred but deletion of extra sequences is incomplete, the IGNs found at the ancestral or trans-locations are likely to be footprints of relatively recent mitochondrial genome evolution.

Animals↗
PubMed2003

Complete mitochondrial DNA sequence of the swimming crab, Portunus trituberculatus (Crustacea: Decapoda: Brachyura).

We determined the complete mitochondrial DNA sequence for a swimming crab Portunus trituberculatus (Miers, 1876) (Crustacea: Decapoda: Brachyura). The entire genome was amplified using a long PCR technique, and the products were subsequently used as templates for direct sequencing using a primer walking strategy. The genome (16,026 bp) contained the same 37 genes (two rRNAs, 22 tRNAs, and 13 proteins) plus the putative control region as found in other arthropods. The gene order of P. trituberculatus was largely identical to those so far obtained for other arthropods such as Drosophila yakuba, although the relative position of the tRNA(His) gene differed from all other arthropods studied so far. While the tRNA(His) gene in other arthropod mitochondrial genomes is located between the ND4 and ND5 genes, that of P. trituberculatus was found between the tRNA(Glu) and the tRNA(Phe) genes, which were located downstream of the ND5 gene. The present gene order could have resulted from tandem duplication occurring in the tRNA(Phe)-ND5-tRNA(His) region (typical gene order in other arthropods) and following deletions of redundant genes. This is the first report of a mitochondrial genome of a brachyuran crab, one of the most diversified and economically important groups of crustaceans.

Animals↗
PubMedDate not supplied

[The role of Cytograpsus angulatus (Crustacea; Brachyura) in the life cycles of Microphallus szidati (Digenea; Microphallidae) and Falsifilicollis chasmagnathi (Acanthocephala; Filicollidae): various aspects of their ecological parasitology].

Based on a study of the larvae from two helminth species parasitizing the crab Cyrtograpsus angulatus Dana, 1851 (Microphallus szidati Martorelli, 1986 and Falsifilicollis chasmagnathi Holcman-Spector et al., 1977), from Mar chiquita lagoom (Argentina) together with the analyses of their life cycles and rates of prevalence, intensity and association coefficient (compared in definitive and intermediate host) the following conclusions have been reached: a) C. angulatus suns to be an excellent intermediate host in the life-cycles of the studied helminths; b) the size of the crabs and the occurrence of natural amputations in the females (Spivak & Politis, in press) appeared correlated with prevalence; c) in the studied crabs the prevalence for F. chasmagnathi is higher in males than in females; d) the intensity did not appear correlated with size and sex of the intermediate host; e) M. szidati and F. chasmagnathi are closely associated with the intermediate host; f) C. angulatus and Himantopus melanurus Vieillot, 1817 (Aves; Recurvirostridae) are reported as new intermediate and definitive hosts, respectively, for F. chasmagnathi; g) Chasmagnathus granulata Dana, 1851 (Crustacea; Brachyura) is reported as a new intermediate host for M. szidati.

Animals↗
PubMed1992

Structural changes in sperm from the fiddler crab, Uca tangeri (Crustacea, Brachyura), during the acrosome reaction.

The acrosome reaction (AR) was induced in sperm from the brachyuran crustacean Uca tangeri either by mixing male and female gametes in filtered seawater or by treating the spermatozoa with the divalent cation ionophore A23187. This latter method provided a sufficient number of reacted spermatozoa to allow a detailed ultrastructural study of the AR. The process consists of two separate phases: a) initial release of the acrosomal vesicle contents, and b) further elongation of the acrosomal filament, which causes reversal of the rigid capsule limiting the acrosomal vesicle contents. The elongate acrosomal filament consists of an apical perforatorium and a basal columnar structure called here the proximal piece. The former derives from the perforatorium of the uninduced sperm stage with only small ultrastructural changes. The proximal piece forms from myelin-like membrane layers which are initially distributed all around the subacrosomal region and then accumulate in a column at the perforatorial base, thus promoting a sudden forward projection of the perforatorium. The AR in brachyurans is thought to be a passive mechanism that utilizes the negative pressure exerted on the nucleus--caused by emptying of the acrosomal vesicle--for an organized accumulation of membrane-rich material immediately behind the perforatorium, with the final result of the raising of a 3 microns long acrosomal filament.

Acrosome↗
PubMed1999

Phylogenetics of Cancer crabs (Crustacea: Decapoda: Brachyura).

We used morphological, mitochondrial DNA sequence, paleontological, and biogeographical information to examine the evolutionary history of crabs of the genus Cancer. Phylogenies inferred from adult morphology and DNA sequence of the cytochrome oxidase I (COI) gene were each well resolved and well supported, but differed substantially in topology. Four lines of evidence suggested that the COI data set accurately reflected Cancer phylogeny: (1) in the phylogeny inferred from morphological data, each Atlantic species was sister taxon to an ecologically similar Pacific species, suggesting convergence in morphology; (2) a single trans-Arctic dispersal event, as indicated by the phylogeny inferred from COI, is more parsimonious than two such dispersal events, as inferred from morphology; (3) test and application of a maximum likelihood molecular clock to the COI data yielded estimates of origin and speciation times that fit well with the fossil record; and (4) the tree inferred from the combined COI and morphology data was closely similar to the trees inferred from COI, although notably less well supported by the bootstrap. The phylogeny inferred from maximum likelihood analysis of COI suggested that Cancer originated in the North Pacific in the early Miocene, that the Atlantic species arose from a North Pacific ancestor, and that Cancer crabs invaded the Atlantic from the North Pacific 6-12 mya. This inferred invasion time is notably prior to most estimates of the date of submergence of the Bering Strait and the trans-Arctic interchange, but it agrees with fossil evidence placing at least one Cancer species in the Atlantic about 8 mya.

Animals↗
PubMed2000

Molecular phylogeny, taxonomy, and evolution of nonmarine lineages within the American grapsoid crabs (Crustacea: brachyura).

Grapsoid crabs are best known from the marine intertidal and supratidal. However, some species also inhabit shallow subtidal and freshwater habitats. In the tropics and subtropics, their distribution even includes mountain streams and tree tops. At present, the Grapsoidea consists of the families Grapsidae, Gecarcinidae, and Mictyridae, the first being subdivided into four subfamilies (Grapsinae, Plagusiinae, Sesarminae, and Varuninae). To help resolve phylogenetic relationships among these highly adaptive crabs, portions of the mitochondrial genome corresponding to the 16S rRNA gene were sequenced for all grapsoid genera occurring in America. The resulting phylogeny confirms most of the present grapsid subfamilies but suggests reclassification of some of the genera and recognition of new taxonomic units. The two American gecarcinid genera might not represent a sister group to the Grapsidae but rather appear to have evolved within the latter. Colonization of inland habitats evolved in several lineages of the grapsoids, resulting in various forms of nonmarine life and different degrees of independence from the sea.

Animals↗
PubMed1995

A developmental study of serotonin-immunoreactive neurons in the larval central nervous system of the spider crab Hyas araneus (Decapoda, Brachyura).

Larval development in crabs is characterized by a striking double metamorphosis in the course of which the animals change from a pelagic to a benthic life style. The larval central nervous system has to provide an adequate behavioural repertoire during this transition. Thus, processes of neuronal reorganization and refinement of the early larval nervous system could be expected to occur in the metamorphosing animal. In order to follow identified sets of neurons throughout metamorphosis, whole mount preparations of the brain and ventral nerve cord of laboratory reared spider crab larvae (Hyas araneus) were labelled with an antibody against the neurotransmitter serotonin. The system of serotonin-immunoreactive cell bodies, fibres and neuropils is well-developed in newly hatched larvae. Most immunoreactive structures are located in the protocerebrum, with fewer in the suboesophaegeal ganglia, while the thoracic and abdominal ganglia initially comprise only a small number of serotonergic neurons and fibres. However, there are significant alterations in the staining pattern through larval development, some of which are correlated to metamorphic events. Accordingly, new serotonin-immunoreactive cells are added to the early larval set and the system of immunoreactive fibres is refined. These results are compared to the serotonergic innervation in other decapod crustaceans.

Aging↗
PubMed2001

Survival and molting of the pea crab larvae Tunicotheres moseri Rathbun 1918 (Brachyura, Pinnotheridae) exposed to copper.

The acute lethal toxicity of copper, as well as its sublethal effect on molting, was studied on larval and postlarval stages of the pinnotherid crab Tunicotheres moseri. The most sensitive stage was zoea I, presenting a significant mortality above 0.5 microg x L(-1). Abnormal setation of the maxillipeds was observed in zoeae II moulted from zoeae I exposed to 100 microg x L(-1) and higher copper concentrations, causing a reduced swimming activity of the larvae. This pathology could be reverted after molting of affected zoea II to megalopa, which would be the first report in crustacean larvae that states the possibility of reverting morphological abnormalities after molting. For zoeae II and megalopae, the inhibition of molting and high mortality was registered at 1,000 microg x L(-1). The effect of copper on the duration of the larval and postlarval stages was differential: It retarded the duration of the stage zoea I, did not modify that of zoea II, and accelerated the ecdysis of the megalopae to first crab. However, precocious molting to megalopae was associated with a smaller body size at the concentration of 100 microg x L(-1). This differential effect of copper on the larval stages throughout the larval development could be ecologically relevant. Because of their lecithotrophia, their short developmental period, their good survival in control conditions, and the high sensitivity showed to copper (especially zoea I), larvae of T. moseri have shown that they are an excellent model for studying the effect of pollutant on survival, molting rate, growth, and morphogenetic changes during development.

Animals↗
PubMed2001

Toxicity of cadmium and copper on larval and juvenile stages of the estuarine crab Chasmagnathus granulata (Brachyura, Grapsidae).

The toxicity of cadmium and copper were assayed in the estuarine crab Chasmagnathus granulata. Acute assays were made on the first larvae stage, and both acute and chronic assays were made on juvenile crabs. The acute lethal toxicity of the assayed heavy metals was three orders of magnitude higher in larvae than in juveniles. Cadmium proved to be more toxic than copper in most cases; this difference was more evident in the chronic assays on juveniles, according to the nonphysiological feature of cadmium and its persistent accumulation in organisms. During these chronic assays, cadmium produced both a significant mortality and a clear retardation of molting, in accordance with its inhibitory effect on the molting process as previously reported. Copper only caused a molting acceleration during chronic assays, perhaps as a detoxifying mechanism. Heavy metal concentrations having effects in the chronic assays have been reported in some sectors of the estuary where the assayed species lives.

Animals↗
PubMed2002

Physiology and morphology of visual movement detector neurons in a crab (Decapoda: Brachyura).

Although visually elicited behaviors have been extensively studied in crabs, their investigation at the neurophysiological level is scant. The present study is a physiological and morphological description of intracellularly recorded and dye injected visual movement detector neurons that respond to the same stimulus that elicits the escape response in the crab Chasmagnathus granulatus. The neurons were investigated in intact animals. The response of movement detector neurons to the danger stimulus (an object moving above the animal) consists of a strong discharge of action potentials frequently superimposed on noisy graded potentials, whereas the response to stationary changes in illumination is weak or undetectable. The response to the moving stimulus is relatively independent of the background intensity and of the contrast between target and background. Repeated presentations of the moving stimulus produce rapid habituation of the neural response. Some of the neurons also respond to mechanical stimulation. These physiological results coincide with those from early studies on visual movement detector fibers of crustaceans achieved by extracellular recordings. However, there are no previous morphological studies of these neurons. Intracellular injection with Lucifer Yellow revealed that these neurons in Chasmagnathus arborize extensively in the internal medulla and in the lateral protocerebrum. They have their somata located in the cell body cluster laying beneath the internal medulla. Their axons project centripetally across the protocerebral tract.

Animals↗
PubMed1993

Localization of toxins in the poisonous mosaic crab, Lophozozymus pictor (Fabricius, 1798) (Brachyura, Xanthidae).

A hot aqueous extraction method was used to extract toxins from different parts of the poisonous coral reef crab, Lophozozymus pictor. Contrary to an earlier report that crab toxins do not show localization, the toxicity of L. pictor was found to be consistently high in the gut and hepatopancreas, whereas the muscle was less toxic and the carapace was mildly or non-toxic. Crabs kept in captivity for 10 days showed reduction in toxicity in all parts studied with almost complete loss of toxicity after 24 days.

Animals↗
PubMed1995

Guanidine neurotoxins are released with the digestive fluid of crabs (Crustacea, Brachyura).

During agonistic interactions intertidal crabs, when exposed to air, produce a foam made of digestive secretions, sea water and air bubbles. They also may release their digestive secretions in water when disturbed. Crabs belonging to the families Majidae, Xanthidae and Portunidae from Atlantic and Pacific areas, not related with human poisoning, possess substances in their digestive secretion which are neurotoxic to mice, block action potentials in nerve preparations, and are reversible on washing. After purification in Bio-gel P-2 chromatography and HPLC analysis, the spontaneously regurgitated secretion, the digestive secretion collected by stomach cannulation of crabs, and the water aquarium replete of intertidal crabs kept overnight show the presence of guanidine neurotoxins.

Animals↗