Xanthoid Crabs Research Articles

A comprehensive molecular phylogeny of the brachyuran crab superfamily Xanthoidea provides novel insights into its systematics and evolutionary history

Maximum likelihood and Bayesian phylogenies for the brachyuran crab superfamily Xanthoidea were estimated based on three mitochondrial and four nuclear genes to infer phylogenetic relationships and inform taxonomy. Habitat data was then used in conjunction with several diversification rates analyses (BAMM, BiSSE, HiSSE, and FiSSE) to test evolutionary hypotheses regarding the diversification of xanthoid crabs. The phylogenies presented are the most comprehensive to date in terms of global diversity as they include all four constituent families (Xanthidae, Panopeidae, Pseudorhombilidae, and Linnaeoxanthidae) spanning all oceans in which xanthoid crabs occur. Six Xanthoidea families are recognised. Panopeidae and Xanthidae sensu stricto are the two largest family-level clades, which are reciprocally monophyletic. Pseudorhombilidae is nested within and is here treated as a subfamily of Panopeidae. Former subfamilies or tribes of Xanthidae sensu lato are basally positioned clades in Xanthoidea and are here assigned family-level ranks: Garthiellidae, Linnaeoxanthidae, Antrocarcinidae, and Nanocassiopidae. The genera Linnaeoxantho and Melybia were recovered in separate clades with Linnaeoxantho being sister to the family Antrocarcinidae, while Melybia was recovered within the family Panopeidae. The existing subfamily classification of Xanthidae and Panopeidae is drastically restructured with 20 xanthid and four panopeid subfamilies provisionally recognised. Diversification-time analyses inferred the origin of Xanthoidea and Garthiellidae in the Eocene, while the other families originated during the Oligocene. The majority of genus- and species-level diversification took place during the Miocene. Ancestral state reconstruction based on depth of occurrence (shallow vs. deep water) shows some ambiguity for the most recent common ancestor of Xanthoidea and Nanocassiopidae. The most recent common ancestors of Antrocarcinidae and Panopeidae were likely deep-water species, while those of Garthiellidae and Xanthidae were probably shallow-water species. Several shifts in net diversification rates were detected but they were not associated with depth-related habitat transitions.

A lifetime amidst fossil crustaceans: a tribute to Joseph S.H. Collins (1927–2019)

To reflect the nearly 65 years of active research into extinct decapod and thoracican crus - taceans (Pleocyemata, Anomura, Brachyura and Cirripedia) by the late Joe Collins, a varied array of papers on polychelid lobsters, paguroid and galatheoid anomurans, brachyurans and scalpellomorph and balanomorph cirripedes is compiled in the present memorial volume. The material described and illustrated originates from a range of sedimentary strata, of Triassic, Jurassic, Cretaceous and Ceno - zoic age in North America (Washington, Oregon and North Carolina), Caribbean (Cuba), Japan and Europe (England, France, Spain, Italy, Switzerland, Slovenia and the Czech Republic). In all, two new genera (one paguroid and a xanthoid crab) and eight new species (all crabs), are erected in the present issue and named after Joe, as a fitting tribute to a well- respected, self- taught scientist.

A new genus and species of xanthoid crab (Decapoda: Brachyura) from offshore hard bank habitats in the Gulf of Mexico.

Speciose populations of small xanthoid crabs on offshore banks and reefs of the northern Gulf of Mexico include a new species that is not assignable to presently named genera. Morphological diagnoses of the new genus and species are underpinned by previously published gene sequence analyses, originally misattributed to another species but now known to apply to this taxon. Herein named Guinope tiara n. gen., n. sp., the species shows molecular phylogenetic affinities with the family Linnaeoxanthidae Števčić, 2005, an ally of panopeid and pseudorhombilid crabs. Specimens from Occulina banks off the Florida Atlantic coast, previously regarded to represent Garthiope barbadensis (Rathbun, 1921), are not that species but instead morphologically assignable to Guinope n. gen. Whether they represent variants of Guinope tiara n. gen, n. sp. or a second species of the genus awaits the collection of fresh materials for DNA analyses.

Morphometric analysis of the mud crab Hexapanopeus paulensis Rathbun, 1930 (Decapoda, Xanthoidea) from the southeastern coast of Brazil

In this study, we estimated the size at onset of maturity (carapace width, CW50) and analyzed the relative growth of some body parts and the heterochely of the mud crab Hexapanopeus paulensis. A total of 800 crabs were collected, from January 1998 to December 1999, on the southeastern coast of Brazil. Each specimen was sexed and measured. CW50 was estimated to be 6.7 mm in males and 6.3 mm in females. Carapace length growth was negatively allometric in both sexes. Cheliped length and height was positively allometric for both males and females. Gonopod growth was isometric (b = 1) and negatively allometric (b 1) for both juvenile and adult females. In males and females, the right cheliped was larger and higher than the left cheliped. Such heterochely may be related to the feeding habits of H. paulensis. Most xanthoid crabs, including the studied species, feed upon mollusks with dextral shells, which require complicated handling. In this sense, the heterochely in H. paulensis might facilitate the food manipulation.

The larval development of <em>Pilumnoides hassleri</em> (Decapoda: Brachyura: Pilumnoididae) reared in the laboratory, with a review of pilumnoidid systematics using larval characters

The genus Pilumnoides is an interesting taxon because its systematic position, based on adult characters, remains unclear. These xanthoid crabs have been related to the Carpiliidae, Goneplacidae and Eriphioidea. P. hassleri A. Milne Edwards, 1880 lives in Brazilian, Uruguayan and Argentinian coasts as far south as the Magellan Strait (southwestern Atlantic). Larvae of P. hassleri from females collected in the harbour of Mar del Plata were reared in the laboratory from zoea I to megalopa and the first larval stage, and described. The species passed through 5 zoeal stages and a megalopa. Larval characters were compared with the previous description of larvae from the southeastern Pacific species P. perlatus and with species of Carpilius , Goneplax and Eriphia in order to review the relationships between these taxa.

Morphometry of the crab Hexapanopeus schmitti (Decapoda: Xanthoidea) on the northern coast of the state of São Paulo, Brazil

A morphometric study of the xanthoid crab Hexapanopeus schmitti was carried out, using the allometric method. Samples were taken monthly for two years (1998-1999) in the Ubatuba region, northern coast of São Paulo, Brazil. Sex and size were assessed for each specimen, and all crabs were measured to obtain their carapace width (CW) and length (CL), abdomen width (AW) of females, major cheliped propodus length and height (PL and PH), and gonopod length (GL) of males. A total of 301 crabs were analyzed, 209 males and 92 females. The CWs of the crabs ranged from 2.5 to 9.8 mm for males and from 2.8 to 9.4 mm for females. The relative growth equation (y=ax^b) based on the relationship between GL and CW suggested that males reach their morphological sexual maturity near 6.1 mm CW. In females, the estimated size at 50 % maturity was 4.8 mm CW, based on the relationship of AW vs. CW. Males reach larger sizes than females, which probably favors their ability to guard the females during courtship. In approximately 83 % of the crabs (n= 371), disregarding sex, the right cheliped was larger.

Southern range extension of two western Atlantic intertidal mud crabs: Panopeus meridionalis Williams, 1984 and Eurypanopeus depressus Smith, 1869 (Crustacea: Brachyura: Panopeidae) in Argentinian waters

Two xanthoid crabs, Panopeus meridionalis Williams, 1984 and Eurypanopeus depressus Smith, 1869 are reported from Mar Chiquita, a coastal lagoon in the warm-temperate region of the southwestern Atlantic. This study documents the presence of a stable population of P. meridionalis in the lagoon, although there have been some sporadic reports of this species in the region before 2000. It reports the first finding of E. depressus in waters south of the Rio de la Plata estuary. The role of Rio de la Plata as a biogeographical barrier is briefly discussed.

Phylogenetic relationships within the coral crab genus Carpilius (Brachyura, Xanthoidea, Carpiliidae) and of the Carpiliidae to other xanthoid crab families based on molecular sequence data

The coral crab genus Carpilius currently includes three widely distributed species that inhabit tropical coral reefs and adjacent waters. The relationship of Carpilius to other xanthoid crabs is unknown. Previously, carcinologists considered Carpilius to be allied with crabs of the family Xanthidae (e.g., Euryozius, Liagore, and Liomera), however, recent workers have considered it to be a monotypic genus within its own family, Carpiliidae. Mitochondrial 12S- and 16S-rDNA gene fragments confirm the monophyly and distinct status of the family Carpiliidae. Within the genus Carpilius, the Caribbean species C. corallinus is basal to the two Pacific species C. maculatus and C. convexus. The Pacific species are sister taxa, despite the greater morphological resemblance of C. corallinus to the Pacific C. convexus. The relationship of the Carpiliidae ( Carpilius) to other xanthoid crabs is investigated, and results of a preliminary analysis of higher xanthoid relationships did not resolve the relationships of Carpiliidae, “Xanthidae,” Menippidae, Trapeziidae, and Ocypodidae to one another. A Menippidae and Carpilius relationship could not be rejected, although a Liomera, Liagore, and Carpilius relationship was.

Symbiosis between an Alpheid Shrimp and a Xanthoid Crab in Salt Marshes of Mid-Atlantic States, U.S.A.

Instances of mutualism and commensalism between alpheid shrimp and other marine invertebrates and fish are common in tropical waters. In this study, we present evidence that the temperate alpheid big-clawed snapping shrimp (Alpheus heterochaelis) participates in a symbiosis with the black-clawed mud crab (Panopeus herbstii), which constructs and maintains burrows in salt marshes of mid-Atlantic states, U.S.A. We surveyed eight mid-Atlantic salt marshes and found that 11% of occupied crab burrows |$(n = 1042)$| also housed Alpheus. Feeding trials showed that whereas Panopeus readily consumes other marsh Crustacea (i.e., grass shrimp and fiddler crabs), it will not prey on snapping shrimp. Alpheus caged in the marsh without access to mud crab lairs could not construct burrows. These results suggest that alpheid shrimps, thought to be limited in distribution to unvegetated mudflats and oyster reefs, may expand their intertidal range by living commensally with Panopeus herbstii in salt marsh habitats.

Brachyuran crabs (Xanthoidea: Xanthidae, Pilumnidae, Menippidae and Trapeziidae) of southern Oman

Thirty-eight species of xanthoid crab are recorded for the first time from Dhofar Province, southern Oman. The geographical range of three species [Nanocassiope alcocki (Rathbun 1902), Actumnus digitalis (Rathbun 1907), and Macromedaeus crassimanus (A. Milne Edwards 1867)] is substantially extended. The pattern of xanthoid species diversity is discussed in relation to the effect of the seasonal monsoon-driven upwelling, and compared with that of other parts of the Western Indian Ocean.

Research on the coast of Somalia. Xanthidae Trapeziidae Carpiliidae Menippidae (Crustacea Brachyura)

Thirty-nine genera and 80 species of xanthoid crabs are identified from recent collections in Somalia and their habitats discussed. Most are new records for Somalia and 23 were previously unknown from the East African coast. Descriptions and illustrations are given for two new species: Cymo lanatopodus and Hypocolpus pardii.

Feeding habits of the pebble crab Eriphia smithi (Crustacea, Brachyura, Menippidae)

Eriphia smithi is a very common East African intertidal xanthoid crab. Its dietary input is based mainly in algal grazing (during the day) and predation (particularly at night). Predation appears quite opportunistic and mostly directed at crustaceans and molluscs, among which bivales largely predominate. Echinoderms are actively avoided and, contrary to common belief, predation on Prosobranchia is only accessory.

On Two New Genera and Five New Species of Xanthoid Crabs From the Collection of His Majesty the Emperor of Japan Made in Sagami Bay

Zwei neue Gattungen und 5 neue Arten der Familie Xanthidae (Decapoda) werden beschrieben. Sie sind alle vom Japanischen Kaiser selbst gesammelt worden, und zwar in der Sagami Bucht.

A North American Xanthoid Crab New to Britain

INVESTIGATIONS of the fauna of artificially warmed docks in Swansea have revealed the presence of xanthoid crabs identified as Neopanope texana sayi (Smith). Specimens agree well with descriptions given by Rathbun1 and Ryan2, and they have been compared with material in the British Museum (Natural History). The previous known distribution of N. t. sayi was along the east coast of North America from Florida northwards to the Gulf of St. Lawrence1,2 and the present record appears to be the first for the British Isles. There are shipping lines which operate between the east coast of North America and Swansea, and it is no doubt by this means that the crab has been accidentally transported. Wolff3 has previously suggested that the crabs Callinectes sapidus Rathbun and Rhithropanopeus harrisi Gould may have reached the coasts of Europe from North America in the ballast tanks of ships, and Neopanope has probably been carried to Britain in, the same manner. In North America N. t. sayi is reported especially from muddy places and on piles among algae2. The habitat is similar in Swansea where specimens have been collected regularly among Ciona intestinalis (L.) and other fouling organisms4 on wooden piles, in a region where the floor of the dock is muddy. The occurrence of the crabs on dock piles and timbers would no doubt enable them or their larvae to find their way into ships' condenser tubes and ballast tanks, in which they could then be transported to a new locality.