Distribution Of Crabs Research Articles

Spatial distribution and population structure of fiddler crabs in an Indian Sundarban mangrove

Brachyuran crabs constitute the most abundant faunal component of mangrove ecosystems and support a wide range of ecosystem services. In the present study, seasonal variation of population density and biomass along with demographic categories and sex ratios of four species of fiddler crabs (Uca rosea, Uca triangularis, Uca dussumieri and Uca vocans) from Jhorkhali Island in the Sundarban mangrove were studied in relation to some major environmental parameters (salinity, nutrient content, soil organic carbon, dissolved oxygen, total dissolved solute, etc.) during bimonthly sampling for three consecutive years (2010-2012). Maximum population density and biomass of the ocypodid crabs were recorded during the pre-monsoonal month and minimum values during the monsoon. Different peaks in reproductive activity were observed among seasonal breeders (U. triangularis, U. dussumieri). For U. vocans, the sex ratio peaks declined during the ovigerous period. All four populations were characterized by significantly more males than females. Multiple regression analysis suggested a cumulative effect of several ecological parameters on seasonal fluctuations of the crab population. Breeding periodicity might be controlled by a combination of factors, including temperature, quality of the substratum, food availability for the adult and larval stages, and intertidal zonations.

Biomass, CPUE and size frequency distribution of blue swimming crabPortunus segnis(Forskal, 1775) in coastal waters of the northern Persian Gulf, Iran

Size frequency distribution, catch per unit effort (CPUE) and biomass of blue swimming crabPortunus segniswere studied in the northern Persian Gulf. A total of 1689 male and 1824 female crabs were collected by swept area method on a monthly basis from May 2010 to September 2012. The populations of male and female crabs were dominated by adult crabs (carapace width >100 mm) from December to May. The juvenile crabs were dominant from June to October and the averages of CPUE did uptrend from June to October. The CPUE increased in full moon and the highest value was observed in shallow coastal areas below 10 m and significantly decreased as depth increased. The maximum CPUE was recorded at 415 and 450 engine powers and the vessel speeds of about 2.5 and 2.8 knots. The monthly biomass estimations showed an upward trend from June to October within the study period, so that the maximum biomass was 110 tonnes in October 2011. Given the CPUE trend and biomass estimation, the results of the present study suggest that October is the optimum time as open fishery season for blue swimming crab in the northern Persian Gulf and the highest CPUE is achievable in shallow coastal areas at less than 10 m depth.

Taxonomy of the freshwater crabs of Costa Rica, with a revision of the genus Ptychophallus Smalley, 1964 (Crustacea: Decapoda: Pseudothelphusidae).

The taxonomy and geographic distribution of the freshwater crabs of the family Pseudothelphusidae Ortmann, 1893, of Costa Rica, Central America, particularly of the genus Ptychophallus Smalley, 1964, are revised. Historical materials deposited in major collections of several institutions were examined, as well as valuable collections in the Zoological Museum of the University of Costa Rica that include abundant specimens obtained recently (2007-2010) in the southern region of the country. The pseudothelphusids of Costa Rica consists of 15 currently valid species belonging to Achlidon Smalley, 1964 (two species), Allacanthos Smalley, 1964 (two species), Potamocarcinus H. Milne Edwards, 1853 (three species), and Ptychophallus (eight species). Two species seem to be restricted to the Atlantic drainage, while seven are known only from the Pacific drainage; six species occur in both drainages. Ptychophallus comprises 13 valid species; four new synonymies are proposed: P. osaensis Rodríguez, 2001, P. campylus Pretzmann, 1968, P. tumimanus ingae Pretzmann, 1978, and P. barbillaensis Rodríguez & Hedström, 2001, as junior synonyms of P. paraxantusi (Bott, 1968), P. tristani (Rathbum 1896), P. tumimanus (Rathbun, 1898), and P. uncinatus Campos & Lemaitre, 1999, respectively. Two species, P. colombianus (Rathbun, 1896) and P. exilipes (Rathbun, 1898), are considered species inquerendae. Lectotype designations are made for P. montanus and P. colombianus. Three species of Ptychophallus are known exclusively from Costa Rica, five exclusively from Panama, and five species occur in both countries; one species appears to be exclusive of the Atlantic drainage, whereas five are known only from the Pacific drainage and seven occur in both drainages. The gonopod morphology of all species is redescribed and illustrated, and maps of their geographic distribution are furnished. A key to the species of Pseudothelphusidae from Costa Rica and to all species of Ptychophallus is provided.

Bárcena Volcano, 1952: a 60-year report on the repopulation of San Benedicto Island, Mexico, with a review of the ecological impacts of disastrous events

Long-term ecological studies are desirable, but rare. I here present data from a 60-year study on the repopulation of San Benedicto Island following a volcano eruption in 1952. Bárcena Volcano appeared on 1 August 1952 on San Benedicto Island, Revillagigedo Islands, Mexico. Within 20 min, the entire island was engulfed in a cloud of ash and pumice, which covered all the plants, killed an estimated 20 000 sea birds within hours and caused the subsequent extinction of an endemic race of rock wren (Salpinctes obsoleta exsul). The results of studies on revegetation and repopulation of the island for the first 10 years after the volcanic eruption were summarised by Brattstrom in 1963. This report extends the studies to 2012. The distribution of the land crab (Aegecarcinus planatus) has increased on the island. By 1971 the crab occurred only over the northern one-eighth of the island, but by 1978 it could be found on one-third of the island. No studies on its distribution have been made since then. Total sea bird populations steadily increased up to 1971 and then rapidly declined, though these changes in numbers are largely due to a fluctuation in the populations of the masked booby (Sula dactylatra). The changes in the booby population may have been due to reproductive and feeding success or to immigration and emigration. The decline in the shearwater (Puffinus ssp.) populations are largely due to erosion and destruction of their burrows; their numbers did not increase until 2000. The formation of a large lava delta created a new habitat, which permitted the establishment of a species of sea bird new to the island, the red-footed booby (Sula sula). Numerous non-resident waifs or stray birds have been observed on the island but most have not become established. The exception is the Laysan albatross (Phoebastria immutabilis), breeding at present in low (3–712) numbers. The original flora consisted of 10 species. The volcano caused four species to become extinct, two re-established themselves, and two species new to the island arrived. There have been marked erosional changes, and the accidental introduction of exotic plants may dramatically alter the vegetation of the island.

Distribution and borrow density of the ghost crabs (genus Ocypode; Ocypodidae) on sandy beaches along the entire coast of Sea of Japan in Hyogo Prefecture, Japan

Distribution and borrow density of the ghost crabs (genus Ocypode; Ocypodidae) on sandy beaches along the entire coast of Sea of Japan in Hyogo Prefecture, Japan

Hermit crabs (Pagurusspp.) at their northernmost range: distribution, abundance and shell use in the European Arctic

Hermit crabs are important components of Arctic benthic systems, yet baseline data on their densities and distribution patterns in this rapidly changing region are still scarce. Here we compile results of numerous research expeditions to Svalbard, the Barents Sea and northern Norway that were carried out from 1979 to 2011 by the Institute of Oceanology, Polish Academy of Sciences. The diversity of hermit crabs at the northern edge of their occurrence is very low; in Svalbard waters only one species ( Pagurus pubescens ) was detected. Another species ( P. bernhardus ), found in northern mainland Norway, north of the Arctic Circle, is likely to extend its distribution northward as the climate warms. Where the two species co-occur, competition between them probably accounts for the smaller sizes and poorer quality shells used by P. pubescens . The composition of the mollusc shells inhabited by these crabs differs between northern Norway and Svalbard, reflecting local mollusc species pools. Hermit crab densities were significantly higher than previously reported (max. mean 10 ind. m −2 ), suggesting their increasing level of dominance in benthic communities in the studied areas. The first to report the distribution of hermit crabs among habitats, this study showed that most individuals occurred at shallow depths (5–150 m), away from glacier termini and on hard bedrock rather than on soft substrata. Keywords : Hermit crabs; Svalbard; Arctic; fjords. (Published: 31 March 2015) Citation: Polar Research 2015, 34 , 21412, http://dx.doi.org/10.3402/polar.v34.21412

Influence of environmental variables on the distribution of intertidal porcellanid crabs in Sepetiba Bay, Rio de Janeiro, Brazil

This study aims to assess the distribution patterns of porcellanid crabs in the intertidal zone of Sepetiba Bay, Rio de Janeiro, Brazil, identifying the abiotic determinants. Samples were collected seasonally (dry and rainy seasons) from January 2005 to August 2007, during low tides in external, intermediate and internal sectors. The crabs were hand caught in consolidated substrates with sampling effort of two people in three different flood zones (lower, medium and higher) for 30 min. Water temperature, salinity, accumulated rainfall, the physical and chemical variables of sediment were analyzed concerning interaction in the distribution patterns of the species. A total of 3,389 crabs, belonging to five genera and eight species, were obtained. With the exception of Petrolisthes armatus, found throughout the intertidal range, all species inhabited the intertidal bottom of Sepetiba Bay exclusively. Favorable environmental conditions of the Sepetiba Bay enabled the success of colonization of several porcellanid species which are a refuge and feeding environment of the Marambaia Island and continental (Junqueira and Ibicui) of the outer zone. The number of species recorded in this study supporting the hypothesis that features of substratum and the availability of food and refuges are factors limiting the establishment of this family in Sepetiba Bay.

Ecotone analysis: assessing the impact of vehicle transit on saltmarsh crab population and ecosystem.

The frequent transit of vehicles (recreational or not) through saltpans and saltmarsh fields has been recorded as one of the major causes of physical and ecological damage for these environments. While several studies have been carried out to assess the consequence of this anthropogenic activity on the different local plant species, little is known on its long-term impact on the faunal community. Invertebrates, such as crabs, provide several essential ecological services, and their presence and abundance are tightly connected to that of the saltmarsh plants. Decrease of vegetative cover due to vehicle transit is likely to cause alterations in the morphology and the composition of the saltmarsh ecosystem. In this study we evaluate presence and distribution of the main crustacean species in several impacted sites in Townsville area (Queensland, Australia), to determine possible correlation between vehicle tracks alterations and crab distribution, as well as investigate any possible habitat shift in the mid- and long-term. Results indicate that reduction of plant cover affects species composition and distribution, with different effects based on the unique characteristics of each crab species analysed, resulting in an overall alteration of the assemblage structure.

Modeling Intertidal Crab Distribution Patterns Using Photographic Mapping Among Tropical Australian Estuaries

Intertidal crabs are abundant in tropical estuaries and have bio-indicator potential. However, the use of intertidal crabs in guiding management actions is limited because high-replication, cost-effective tools to analyze their distribution patterns at large scales are lacking. This study used assemblage modeling and photography to rapidly build formal understanding of the spatial organization of crab communities in the low intertidal zone, between mean sea level at low spring tide and the edge of the mangrove forest, within and among estuaries. A classification and regression tree model revealed seven distinct habitats based on relative occurrence of five species (Uca coarctata, Uca seismella, Macrophthalmus japonicus, Metopograpsus frontalis, and Metopograpsus latifrons) among eight estuaries along 160 km of coast in North Queensland, Australia (18° 28′–19° 25′ S, 146° 12′–147° 14′ E), across four sampling trips between April 2009 and October 2010. Photography provided high-replication sampling across a large area relative to the aim of the study but did not represent the whole intertidal crab community. Complementary hand collections within one estuary allowed the occurrences of three other species (Perisesarma longicristatum, Australoplax tridentata, and Metopograpsus thukuhar) to be fitted into the model. Species occurred across habitats, yet a high occurrence of different species characterized each habitat. The presence of some species not usually found on low intertidal banks suggested connectivity across the intertidal landscape. The model provided a formal basis to add previous small “site or transect specific” scale spatial distribution knowledge as well as other ecological information. Areas with outlying values can be identified as research and management priorities in the absence of other information, although this prioritization should be done with care. The approach may be transferable to other organisms and systems to provide rapid, cost-effective information on the distribution of key fauna where background understanding and resources are limited.

Shell selection behaviour and spatial distribution of three species of intertidal hermit crabs from Hormuz Island, Persian Gulf (Crustacea: Paguroidea)

Shell selection behaviour and spatial distribution of three hermit crab species, Diogenes avarus, D. karwarensis, and Areopaguristes perspicax, were studied at six sites along the intertidal zones of Hormuz Island in the Persian Gulf. 1025 specimens were collected occupying altogether 31 shell species (D. avarus 28 species, A. perspicax 22 species, and D. karwarensis 8 species). Diogenes avarus was found to be by far the most abundant of these three crab species, and Cerithidea cingulata the dominant shell occupied by these hermit crabs. The distribution of the hermit crabs significantly varied (p<0.05) among the sites. The number and the wide diversity of shells occupied in different sites show that the main factor in shell selection for these hermit crabs is the abundance and distribution of shell species in the field.

The distribution of the European shore crab, Carcinus maenas, with respect to mangrove forests in southeastern Australia

There is growing interest in associations between non-native species and native foundation species. Along the southeast coast of Australia, the European shore crab, Carcinus maenas, overlaps with the distribution of the grey mangrove, that provides refuge to many native invertebrates from predators and physiological stress. We tested the hypothesis that C. maenas would be more abundant under the canopy of mangrove forests than in adjacent unvegetated intertidal habitat. Trapping surveys within three estuaries found greater abundances of C. maenas in mangrove forests than in adjacent unvegetated habitat and, within mangrove forests, under the canopy than in the pneumatophores zone. Average temperatures under the mangrove canopy were up to 2°C lower than in unshaded habitats and maximum temperatures up to 5.7°C less. The results of tethering studies did not support the hypothesis that predatory mortality of C. maenas was reduced in mangroves. To the contrary, survivorship of tethered crabs was much lower under the mangrove canopy than in adjacent unvegetated habitat. Habitat choice experiments, however, indicated that crabs chose shaded and protected over unshaded and exposed habitat. Hence, along this coastline where summertime maximum air temperatures may approach the known LD50 of C. maenas (40min at 40°C), mangroves may help to facilitate persistence in intertidal habitats. Our study adds to a growing number indicating that foundation species may not only facilitate native species, but non-native species too. Additional studies are now needed to confirm the mechanism of the association between C. maenas and mangroves in eastern Australia.

Patterns in connectivity and retention of simulated Tanner crab (Chionoecetes bairdi) larvae in the eastern Bering Sea

The eastern Bering Sea (EBS) population of Tanner crab (Chionoecetes bairdi) has exhibited high variability in recruitment to the commercially exploited stock since the late 1970s. Concurrently, apparent shifts in crab distribution have also been observed. Larval advection patterns and associated local retention offer a potential mechanism for these observations. The Regional Ocean Modeling System (ROMS) was used to simulate larval Tanner crab advection patterns over 1978–2004 based on larval hatching sites inferred from the distributions of reproductive females sampled during annual National Marine Fisheries Service trawl surveys. Connectivity among EBS subregions was examined by comparing start and end float locations after 60days of simulated drift. High levels of retention (>50% of floats) were observed in the majority of source subregions, and contributed significantly to the total number of endpoints in each region. Patterns in advection and resultant interregional connectivity were variable, with strongest sustained connectivity occurring along shelf, within individual domains. Increased settlement potential in the outer domain and southern middle domain after 1990 is consistent with an observed geographic shift in fishery productivity. Apparent reliance of Bristol Bay on local larval retention validates recent spatial fishery management to conserve this area as a subpopulation.

Vertical distribution by demographic groups of ghost crab Ocypode quadrata (Crustacea: Brachyura)

The ghost crab Ocypode quadrata plays an important role in energy transfer between trophic levels, and has been widely used in evaluations of impacted environments. In order to provide data on the biology of this potential bioindicator species, the population structure and vertical distribution of individuals were studied on two beaches in southeastern Brazil. Each beach was divided into quadrants of 1000 m2 with boundaries of upper, middle and lower levels in relation to the waterline. Collected monthly by active searching through one year, the specimens of O. quadrata were sexed, measured for carapace width, and returned to the beach. Of the total of 1904 specimens collected, the largest proportion (46.2%) were males, followed by 31.4% juveniles. The vertical distribution of the ghost crabs differed among age groups: males mostly occupied the middle and upper levels; adult females, ovigerous or not, were more abundant in the lower level; and juveniles were evenly distributed in all levels, with a slight tendency toward the middle. The sex ratio favored males in a few months of the year and in the larger size classes. The abundance of O. quadrata is limited by low temperatures, and its spatial and temporal distribution is controlled by food availability and ease of reproduction. Knowledge of the biology of these crabs is essential in order to use them as a bioindicator species; the vertical distribution patterns may reflect changes in the beach hydrodynamics or other environmental factors.

Horizontal distributions of Dungeness crab (Cancer magister) and red rock crab (Cancer productus) larvae in the Strait of Georgia, British Columbia

Abstract The supply of planktonic larvae to adult populations is an important contributor to the spatial and temporal variability of benthic marine organisms. The ability to predict spatial patterns of larvae and recruits from the physical and biological processes that facilitate dispersal is required in order to advise and evaluate conservation and fisheries management decisions. In the present study, the horizontal distribution of Dungeness crab (Cancer magister) and red rock crab (Cancer productus) zoeae was described from surveys conducted in the Strait of Georgia in the spring of 2009 and 2010. Processes that may be responsible for generating spatial variability of larvae were evaluated based on (i) horizontal overlap between larvae and water properties, (ii) spatial dependence of larvae and water properties, and (iii) changes in the dispersion of stage-specific distributions. Interspecific variability between horizontal patterns of the first and second larval stages was primarily attributed to differences in the distribution of larval release locations, which appeared to be restricted to the southern and central strait for C. magister. Potential effects of physical processes on larval distributions are also discussed.

The distribution of hermit crabs and their gastropod shells on shallow reefs off St. John, US Virgin Islands

Using the coral reefs of St. John, US Virgin Islands, as an experimental system, we tested the hypothesis that the distribution of hermit crabs (Calcinus tibicen Herbst, 1791 and Pagurus brevidactylus Stimpson, 1859) is associated positively with the distribution of the cerithid gastropods shells they favor as homes. Cerithium spp. were surveyed on shallow (<6 m) reefs along 10 km of the south shore of St. John, in 2011 (6 sites) and 2012 (7 sites); they were categorized as live shells (LS), empty shells (ES), or occupied shells (OS, containing hermit crabs). In both years, densities of LS and ES differed significantly among sites and were higher in the east compared to the west; densities of OS did not vary among sites in 2011, but in 2012 were marginally more abundant to the west. Densities of OS were not correlated with the density of LS in either year. The distribution of cerithids is consistent with the hypothesized origin in a patch-depletion model for larval supply, in which recruitment declines along the shore as larvae are transported farther from their eastern sources. In contrast, the distribution of hermit crabs was more uniform along the shore, suggesting dispersal in the pelagic realm or on the benthos was more active than for cerithids. Hermit crabs did not occur simply where live cerithids were found, but instead favored locations where suitable shells (i.e., OS + ES of sufficient size) were common, and potentially dispersed to these locations.

Herbivory drives the spread of salt marsh die-off.

Salt marsh die-off is a Western Atlantic conservation problem that has recently spread into Narragansett Bay, Rhode Island, USA. It has been hypothesized to be driven by: 1) eutrophication decreasing plant investment into belowground biomass causing plant collapse, 2) boat wakes eroding creek banks, 3) pollution or disease affecting plant health, 4) substrate hardness controlling herbivorous crab distributions and 5) trophic dysfunction releasing herbivorous crabs from predator control. To distinguish between these hypotheses we quantified these variables at 14 Narragansett Bay salt marshes where die-off intensity ranged from <5% to nearly 98%. Nitrogen availability, wave intensity and plant growth did not explain any variation in die-off. Herbivory explained 73% of inter-site variation in die-off and predator control of herbivores and substrate hardness also varied significantly with die-off. This suggests that salt marsh die-off is being largely driven by intense herbivory via the release of herbivorous crabs from predator control. Our results and those from other marsh systems suggest that consumer control may not simply be a factor to consider in marsh conservation, but with widespread predator depletion impacting near shore habitats globally, trophic dysfunction and runaway consumption may be the largest and most urgent management challenge for salt marsh conservation.

Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 20:53-67 (2014) - DOI: https://doi.org/10.3354/ab00545 Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil Kelsey R. Hampton1, Melanie J. Hopkins2, John C. McNamara3, Carl L. Thurman1,* 1Department of Biology, University of Northern Iowa, Cedar Falls, Iowa 50614-0421, USA 2GeoZentrum Nordbayern, Universität Erlangen-Nürnberg, Loewenichstraße 28, 91054 Erlangen, Germany 3Departamento de Biologia, FFCLRP, Universidade de São Paulo, Ribeirão Preto 14040-901, São Paulo, Brazil *Corresponding author: thurman@uni.edu ABSTRACT: Isolation due to geographical barriers should promote genetic and morphological divergence among populations. Marine currents flowing in opposing directions along landmasses can constitute barriers that isolate populations dependent upon aquatic dispersal. The distribution of fiddler crabs (genus Uca) is regulated primarily by the oceanic transport of their planktonic larvae and by available adult habitat. Along the Brazilian coast of eastern South America, the flow of 2 major oceanic currents separates northern from southern Uca populations, which may promote intraspecific divergence in ‘trans-Brazilian’ species. Populations of 10 Uca species were sampled at 64 locations north and south of the Ponta do Calcanhar, Rio Grande do Norte, Brazil. Carapace shape was assessed using geometric morphometrics to analyze 12 surface landmarks in 1319 female crabs. Carapace shape differs significantly in each species. In morphospace, the carapace forms of the 10 species appear to separate into traditional subgeneric clusters. Within the 8 species exhibiting trans-Brazilian distributions, northern and southern populations show distinct carapace differences. Depending on species, either the hepatic or the branchial region is larger in northern populations. Since significant genetic variability among such populations has not been confirmed, divergence in carapace shape suggests significant ecological modulation of phenotype within each species. Apparently, environmental differences between northern and southern localities exert a greater impact on carapace morphology than impeded gene flow. The drivers underpinning diversification of carapace shape remain unknown, however. KEY WORDS: Brachyura · Fiddler crab · Uca · Structural variation · Landmark analysis · Isolation · Ecophenotypy Full text in pdf format Supplementary material PreviousNextCite this article as: Hampton KR, Hopkins MJ, McNamara JC, Thurman CL (2014) Intraspecific variation in carapace morphology among fiddler crabs (Genus Uca) from the Atlantic coast of Brazil. Aquat Biol 20:53-67. https://doi.org/10.3354/ab00545 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 20, No. 1. Online publication date: January 13, 2014 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2014 Inter-Research.

Intra-guild predation among early benthic phase red and blue king crabs: Evidence for a habitat-mediated competitive advantage

The apparent shift in predominance of commercial crab species from blue king crab (Paralithodes platypus) to red king crab (Paralithodes camtschaticus) around the Pribilof Islands, Alaska, USA, may be driven by ecosystem-level processes such as competitive displacement or predation during early life stages. Specifically, intra-guild predation among species during the early benthic phase might be a source of mortality limiting blue king crab population recovery. In a laboratory experiment, we evaluated how varying ratios of prey species (year-0 blue and red king crabs) and habitat type (shell and cobble) affect prey preference of year-1 red king crabs. Year-0 red king crabs were preferentially consumed over blue king crabs in shell habitat, but not cobble, likely because the smaller interstitial spaces in shell reduced predator foraging efficiency and predator–prey encounter rates. Blue king crabs had high levels of crypsis regardless of habitat type or predator presence/absence, while red king crabs were less cryptic overall compared to blue king crabs, but crypsis increased when predators were present. Preference for red king crabs in shell may reflect divergent adaptations between species for minimizing predation. Blue king crab's light, mottled coloration and relatively smooth, flat carapace is well adapted for visual and physical crypsis in shell habitat, while the monochromatic, dark coloration and pronounced spination of red king crabs may make them more conspicuous. Our results show that habitat can mediate intra-guild predation between Paralithodes species and suggest that shell material may provide blue king crabs a competitive advantage over red king crabs. The extent of shell habitat may be an important factor regulating blue king crab distribution or the recovery of depleted populations around the Pribilof Islands.

Mangrove sedimentary characteristics and implications for crab Ucides cordatus (Crustacea, Decapoda, Ucididae) distribution in an estuarine area of the Amazonian region

At the coastal zone sediments, water and organisms interact intensely. At equatorial tidal-dominated coast mangroves are abundant. These areas are well-known for their ecological importance. Considering the mangroves of Atlantic South America, the mangrove crab, Ucides cordatus has ecological and economic prominence. High densities of this crab are found on the Amazon coast. This study investigates the sediment distribution of the Bragança mangrove area (Amazon coast, Brazil) and its correlations with vegetation and mangrove crab distribution. Sediments of 47 sites, as well as crabs from sites with different sediment and vegetation, were sampled. Results show that surface sediment of the area is mainly composed by silt (59%), with 21% sand and 20% clay. Variations in sorting and skewness are the product of local variations in clay and sand content. The vegetation type was significantly correlated to mangrove crab characteristics, abundance and weight/size. Sediment characteristics are also substantially different according to the vegetation type. Areas where Avicennia germinans prevails have more sand and clay than areas of Rizophora mangle, in which silt is dominant and crabs were significantly heavier. The present results have showed that the distribution of sediments, crabs and vegetation at mangrove areas are strongly correlated. Thus, they should be studied in conjunction.

Description of a new species of the genus Trichopeltarion A. Milne-Edwards, 1880 (Decapoda: Brachyura: Trichopeltariidae) from western Pacific and southeast Asian waters

The present study limits the distribution of a deep-sea crab, Trichopeltarion ovale Anderson, 1896, to the Indian Ocean, and describes a new species of what has been referred to as T. ovale from the western Pacific and southeast Asia. Trichopeltarion danieleae sp. nov. differs morphologically from allied congeners by a combination of characters of the carapace and ambulatory legs. The new species is also distinguished from two fossil Trichopeltarion species, T. huziokai (Imaizumi, 1951) and T. inflatus (Kato, 1996).