Species Of Xanthid Crabs Research Articles

Remarkable bilaterally asymmetrical gonopores and gonopods in a new genus and species of brachyuran crab from the Ryukyu Islands, Japan (Decapoda: Brachyura: Xanthidae)

AbstractA new genus and new species of xanthid crab, Mabui calculusn. gen., n. sp., are described from Okinawa Island, Ryukyu Islands, Japan. The new taxon is unique for Brachyura by having bilaterally asymmetrical male gonopods and female gonopores, with the particular reproductive structure always distinctly more developed on one side than in the other. This remarkable condition, so far unique among brachyurans, was observed in all specimens examined (N = 53), except for an undeveloped subadult female. The right chelae of all intact males and large females are almost always larger than the left chela, and each right chela has a large and modified cutting tooth. Other than in the asymmetrical external reproductive structures, the new taxon is morphologically closest to the xanthines Megametope ogaensis Sakai, 1974 and Jacforus cavatus (Rathbun, 1907), but can easily be distinguished by the characters of the carapace, third maxilliped, ambulatory legs, and male pleon.

Actaea grimaldii, a new species of reef crab from Papua New Guinea (Crustacea, Brachyura, Xanthidae)

A new species of xanthid crab, Actaea grimaldii, is described from the coral reefs of Papua New Guinea. This species has a distinctive red and white coloration and is closest to Actaea spinosissima Borradaile, 1902, from the Indian Ocean. However, the new species can be distinguished by the arrangement of spines on the carapace, chelipeds and ambulatory legs, and the structure of the male gonopods. Actaea grimaldii sp. nov. has also been confused with A. polyacantha (Heller, 1861), but differs markedly in the carapace armature.

A new species of ocellated Xanthias Rathbun, 1897 (Crustacea: Decapoda: Brachyura: Xanthidae) from the Bohol Sea, Philippines.

A new species of xanthid crab (Brachyura: Xanthidae) is described from the Bohol Sea in the central Philippines. Xanthias joanneae sp. nov. is most similar in morphology to X. maculatus Sakai, 1961 (type locality: Sagami Bay, Japan), particularly in the presence of distinctive ocelli on the carapace and pereopods. It can be separated from this species by the greater number of ocelli on the dorsal surface of the carapace, wider teeth separated by narrow notches on the carapace anterolateral margin, absence of longitudinal ridges on the external surface of the chelar palm, shorter and stouter ambulatory legs, narrower male anterior thoracic sternum, and stouter G 1.

First report of two rare xanthid crabs (Crustacea: Decapoda: Brachyura: Xanthidae) from Pakistan

Two rare species of xanthid crab (Brachyura: Xanthidae) are reported for the first time in the territorial waters of Pakistan. Odhnea echinus and Paraxanthodes cumatodes were collected from Sonmiani Bay, on the coast of Pakistan. These species are known from only a few specimens and localities globally. The male gonopods are figured for the first time for these two species, and updates on their taxonomy are also provided.

On a new genus and new species of xanthid crab (Crustacea, Decapoda, Brachyura, Xanthinae) from the South China Sea, with notes on the genus Liagore De Haan, 1833

A new genus and new species of xanthid crab, Ovatis simplex, is described from the South China Sea. The genus is closest to Liagore but can be distinguished by a suite of carapace and male gonopod characters. The systematic position of Liagore is also considered, and both genera, Liagore and Ovatis, are here referred to the subfamily Xanthinae. Comparisons with the allied genera, Paratergatis and Pulcratis, are also provided.

Hexapanopeus manningi, a new xanthid crab (Crustacea, Decapoda, Xanthidae) from Brazil

A new species of xanthid crab, Hexapanopeus manningi, closely related to H. caribbaeus Stimpson, 1871 collected from mangrove areas in the estuaries of Rio Grande do Norte. Brazil is described. This is the sixth species of Hexapanopeus Rathbun, 1898 from Brazil. Distinguishing features of the species are also mentioned to facilitate its separation from closely related species.

A new late Maastrichtian xanthid crab from southern Limburg (The Netherlands)

A new species of xanthid crab, Xanthosia semiornata, and claw fragments placed, with reservation, in Aulacopodia riemsdyki Bosquet, 1854, are described from the late Maastrichtian Meerssen Member (Maastricht Formation) in the type area of the Maastrichtian Stage, SE Netherlands.

Description of a new species of Demania Laurie, 1906 (Crustacea, Decapoda, Brachyura, Xanthidae) from the Bay of Bengal, Indian Ocean

A new species of xanthid crab, Demania bangladeshensis sp. nov., is described from the Bay of Bengal, Indian Ocean. Demania bangladeshensis appears to be most closely related to Demania toxica Garth, 1971, a poisonous species from the Philippines, but can easily be separated by the differently sculptured carapace, legs and chelipeds.

Palytoxin in two species of xanthid crab from the Philippines.

Two species of xanthid crab, Lophozozymus pictor and Demania alcalai, known to cause fatal poisoning when ingested, were collected on southern Negros, Philippines. They were highly fatal by mouse assays. The toxin in both species was identified as palytoxin, a highly lethal toxin of zoanthids, by chromatographic and mass spectrometric analyses. The toxin was found in all tissues but the concentrations were higher in the gills, viscera, and eggs.

The occurrence of paralytic shellfish toxins in two species of xanthid crab from Suva barrier reef, Fiji Islands

Five species of crabs commonly occurring on Suva barrier reef, Fiji Islands, were tested for the presence of paralytic shellfish toxins. All 35 specimens of Atergatis floridus and all 18 specimens of Zosimus aeneus tested were lethal to mice, whilst none of 12 specimens of Carpilius maculatus, 8 of C. convexus and 10 of Eriphia sebana tested were lethal. A. floridus contained saxitoxin (55 – 60%), neosaxitoxin (35 – 40%), gonyautoxin-II (less than 5%) and a new toxin previously found in a toxic dinoflagellate, Pyrodinium bahamense var. compressa, and tentatively coded PBT (1%). Z. aeneus contained the same components, with additional trace amounts of gonyautoxin-I and III, but neosaxitoxin was the major component in this species. Comparison with the results of testing Okinawan specimens of Z. aeneus, A. floridus and Platipodia granulosa suggests that the toxin profile is specific to species.

Analysis of paralytic shellfish toxins of xanthid crabs in okinawa.

Screening of paralytic shellfish toxins in the marine organisms living on the coral reefs revealed that three species of xanthid crabs, Zosimus aeneus, Atergatis floridus and Platypodia granulosa, contained high amounts of toxin, ranging from 180 to 590 MU/g. Weak toxicity was detected in the spider conch Lambis lambis, but other specimens including two bivalves were negative, indicating the causative organism is not planktonic but benthic. A. floridus and Z. aeneus contained neosaxitoxin as the major component and saxitoxin and gonyautoxin II as minor ones. A trace amount of gonyautoxin I was also detected in Z. aeneus. Unlike these two species, P. granulosa contained only saxitoxin. The toxin compositions of these crabs were distinctly different from those of the marine snails living in the same environment in lacking the new toxincoded TST.

Behavioral response to hydrostatic pressure in larvae of two species of xanthid crabs

Responses of pelagic larvae of two species of xanthid crabs to manipulations of hydrostatic pressure were examined and compared. One species, Rhithropanopeus harrisii (Gould), is a temperate estuarine species, while the other, Leptodius floridanus (Gibbes), inhabits shallow water and reefs in tropical and subtropical regions. All zoeal stages of R. harrisii detected pressure stimuli presented in increments as small as 0.025 atm. Both Stage I and II zoeae of L. floridanus responded to pressure stimuli presented in increments of 0.1 atm. Stage I responded when pressure was changed by the smallest increment tested, 0.025 atm, but Stage II did not. L. floridanus zoeal Stages III and IV, however, did not change vertical position relative to control larvae when subjected to pressure stimuli. The capacity of R. harrisii zoeae to respond to changes in hydrostatic pressure may be related to their retention in the estuarine environment. In L. floridanus, a non-estuarine species, the pressure response is important only in the first zoeal stage and may function promarily in dispersal.

The influence of light in the depth regulation of crab larvae.

1. Experiments were conducted to determine the phototaxis responses of each larval stage of two species of Xanthid crabs and to assess the influence of light on depth regulation.2. Two primary orientations in response to light are described.3. Secondary orientation in response to light results in positive phototaxis in all four zoea stages and the megalopa of each species.4. In response to changes in light intensity, the first zoea stage of P. herbstii demonstrated high photokinesis. Although some increase in swimming rate in response to increased light intensity was noted in larvae of L. floridanus, particularly in the first zoea stage, the differences were not statistically significant. It is suggested that larvae of L. floridanus may swim at their capacity at low light intensities, in contrast to larvae of P. herbstii.5. Light response dominates that of gravity in the first zoea stage; in the megalopa, gravity response dominates that of light in a majority of individuals.6. Light aimed down the axis of the observation tank exerts a negligible effect upon the net vertical distribution of the first zoea stage. However, the net distribution of later larval stages is shallower in light than is the case in darkness.7. The response of the larvae to light thus superimposes diurnal vertical migration upon the basic pattern of differential vertical distribution through ontogeny. These two characteristics of larval development will result in considerable vertical scattering during the dispersal phase.

Metabolic rate in relation to body size and environmental oxygen concentration in two species of xanthid crabs

The standard metabolic rates of Menippe mercenaria and Panopeus herbstii over a wide range of body weights and at different environmental O 2 concentrations were determined. The uptake of O 2 by digestive gland tissues from these crabs, in vitro, was measured. 1. 1. The standard metabolic rates of M. mercenaria and P. herbstii are proportional to body weight to the 0·86 and 0·80 powers respectively. 2. 2. The per g O 2 consumption of digestive gland tissues, in vitro, likewise decreases as the body size of the crab increases. 3. 3. The effect of reduced O 2 concentration on the metabolic rates of these crabs appear to be relatively constant from 0·8 to 5·6 ml O 2/l. water.

オウギガニ科の3種の毒ガニの毒性試験

The toxicity of three species of xanthid crab, Zosimus aeneus, Platypodia granulosa and Atergatis floridus, was determined by a mouse bioassay method. The toxin was detected in the specimens caught at various places around Japan, and a remarkable variation of toxicity was observed in each species. The appendages were usually more poisonous than the cephalothorax. In a strongly toxic specimens of Z. aeneus the exoskeleton of cephalothorax and the viscera contained a considerable amount of toxin, together with the exoskeleton and the muscles of appendages. No obvious difference of lethality was observed between male and female, while a fairly distinct local variation of toxicity was seen. Z. aeneus was more toxic than the others.

Cephaloidophora carpilodei n. sp. and C. pinguis n. sp., Gregarines of a Xanthid Crab in Hawaii*†

SYNOPSIS. Carpilodes rugatus from Coconut Island, off the windward side of Oahu, was infected to the extent of 65% with intestinal gregarines. Infection was frequently heavy, especially with the intracellular stages. Two new species of Cephaloidophora are described. C. carpilodei n. sp. showed multiple infections in single host cells; as many as three fully developed trophozoites were found in one intestinal epithelial cell of the mid‐gut. C. pinguis n. sp. was markedly different morphologically from C. carpilodei. In both species, intracellular development was prolonged with eventual production of septate trophozoites larger than the host cell. The gregariousness of the hosts was believed to facilitate intraspecific infection.Although other species of Xanthid crabs from the immediate vicinity were examined for gregarines, the other host species either were not parasitized or they contained gregarines belonging to species different from those found in C. rugatus. This was true even of host species placed in the same genus. Failure of these parasites of C. rugatus to become established in other species of Xanthids living in such close proximity is evidently due to biochemical or physiological barriers in the latter forms.