Larval development of Maja crispata Risso 1827 (Crustacea,Decapoda, Majidae) reared in the laboratory

The morphology of the zoea and megalop of Maja crispata are described from laboratory-reared material, and compared with other two spider crabs belonging to the subfamily Majinae, Maja squinado and Maja goltziana, recorded in the same region of the eastern Atlantic. The diagnostic characters allowing the separation of these species' larvae are tabulated and discussed.     

A new genus of freshwater crab (Crustacea: Decapoda: Brachyura: Potamidae) from Thailand,with a description of a new species

A new genus, Stelomon, is established for the Thai freshwater crabs Potamon kanchanaburiense Naiyanetr, 1992, and P. pruinosum Alcock, 1909. The unique structure of the male first pleopod is the key diagnostic generic character. One new species, which differs in the form of the male first pleopod, is also described. A key to the species of Stelomon is included.     

Two new genera of the family Pilumnidae (Crustacea: Decapoda: Brachyura) from Queensland,Australia

Two new genera of Pilumnidae each with a single new species are described from southeastern Queensland waters. Priapipilumnus is defined by the greatly swollen base and simple blunt apex of the male first pleopod and the concomitant posteriorly protruding, bilobed, third abdominal segment. Takedana is separable by the very short spinous anterolateral margins, the swollen branchial regions, the moderately short walking legs, and the strongly spined chelae. Actumnus pugilator is reassigned to Bathypilumnus Ng and Tan, 1984.     

The zoeal development of Nanocassiope granulipes (Sakai, 1939) (Crustacea: Decapoda: Brachyura: Xanthidae) described from laboratory-reared material

Ovigerous crabs of Nanocassiope granulipes (Sakai, 1939) were collected in South Korean waters and their larvae reared in the laboratory. Four zoeal stages are described and illustrated in detail. Morphological characteristics of zoea I, such as the antennal exopod, the endopod of the second maxilliped and the telson, are compared with other known first-stage zoeas from the Xanthinae. The firststage zoea of N. granulipes appears to be similar to those of Leptodius exaratus (H. Milne Edwards, 1834) and Macromedaeus distinguendus (de Haan, 1835).     

Establishment of a new subfamily for Shenius anomalus (Shen, 1935) (Crustacea: Decapoda: Brachyura: Dotillidae)

Shenius anomalus (Shen, 1935 Shen, CJ. 1935. On some new and rare crabs of the families Pinnotheridae, Grapsidae and Ocypodidae from China. Chin J Zool., 1: 19–40. 15 figures [Google Scholar]) has previously been assigned to the Macrophthalmidae Dana, 1851, and the Camptandriidae Stimpson, 1858 Serène, R. 1974. Note on the genera and species of the Camptandriinae Stimpson, 1858 (Decapoda, Brachyura: Ocypodidae). Treubia, 28(3): 59–117.  [Google Scholar]. A close examination of adult and first stage zoeal morphology confirms some previous suggestions that S. anomalus is actually an anomalous member of the Dotillidae Stimpson, 1858 Serène, R. 1974. Note on the genera and species of the Camptandriinae Stimpson, 1858 (Decapoda, Brachyura: Ocypodidae). Treubia, 28(3): 59–117.  [Google Scholar]. However, because a number of distinctive features distinguish it from all other dotillid genera a new subfamily Sheniinae is established.     

Hypersymbioses in the pinnotherid crabs (Decapoda: Brachyura: Pinnotheridae): a review

Members of the brachyuran family Pinnotheridae are nearly all symbionts of other invertebrates; some crabs are parasitic and others are commensal. Most live inside bivalve molluscs or in the tubes or burrows of polychaetes and other marine organisms. Animals living on or in pinnotherid crabs are considered to be hypersymbiotic and are reviewed here. Hypersymbionts are poorly represented within only 26 members (～8.6%) of the Pinnotheridae (20 species in the subfamily Pinnotherinae and six species in the Pinnothereliinae). Parasitic hypersymbionts are as follows: three species of fungi; one cestode larva (undescribed procercoid of Trypanorhynchida); one trematode metacercaria (undescribed Microphallidae); nematode cysts (undescribed); three species of Nemertea (Carcinonemertidae, two undescribed); two species of rhizocephalan Cirripedia (Sacculinidae; plus five or more undescribed potential sacculinid species); epicaridean Isopoda [13 species of Bopyridae (one undescribed) and four species of entoniscids (Entoniscidae, three undescribed)]. Preliminary biological information on undescribed entoniscids is presented. Several mainly incidental hypersymbioses involving ectosymbionts are known primarily from Pinnixa chaetopterana, a symbiont of polychaete burrows. The ctenostome bryozoan Triticella elongata is the only known obligate ectosymbiont in P. chaetopterana, but it also infests five other species of pinnotherids. Some of the other ectosymbionts (all incidental) on P. chaetopterana are stalked ciliates, hydroids, juvenile polychaetes, bivalve molluscs, balanomorph barnacles, harpacticoid copepods and urochordates. Species of ectosymbionts including an ectoproct bryozoan have been reported from other pinnotherid species. Factors influencing our meagre knowledge of hypersymbioses in the Pinnotheridae are discussed, among them the inaccessibility of crab hosts and research emphasis on taxonomy within the family.     

Re-establishment of the Family Eumedonidae Dana, 1853 (Crustacea: Brachyura)

On the basis of a re-examination of all available data concerning the systematic position and status of the genus Eumedonus and allied genera it is concluded that these taxa form a separate family within the superfamily Xanthoidea (sensu Guinot, 1978). The family is characterized not only by particular morphological features but by the symbiotic mode of life of its members.     

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.     

A revision of the family Deckeniidae Ortmann, 1897 (Crustacea: Decapoda: Brachyura: Potamoidea), with description of a new genus (Gecarcinucidae: Gecarcinucoidea) from the Seychelles,Indian Ocean

The family Deckeniidae Ortmann, 1897, is revised and only 2 East African species are recognised, D. imitatrix Hilgendorf, 1869, and D. mitis Hilgendorf, 1898. The identity of the poorly known species from Seychelles, Indian Ocean, Deckenia alluaudi A. Milne Edwards and Bouvier, 1893, is clarified. This species is redescribed, assigned to a new genus (Seychellum gen. nov.), removed from the Deckeniidae sensu stricto and transferred to the family Gecarcinucidae Rathbun, 1904.     

Parasites of shore crabs in the genus Hemigrapsus (Decapoda: Brachyura: Varunidae) and their status in crabs geographically displaced: a review

Two brachyurans of the varunid genus Hemigrapsus from the northwestern Pacific Ocean have invaded coastal regions of the north Atlantic – Hemigrapsus takanoi (sibling species of Hemigrapsus penicillatus) and Hemigrapsus sanguineus in Europe and the latter in the USA. Parasites are known from these crabs in their native habitats, but except for an undescribed larval nematode, none has been found in those examined from their new locations. These parasites include metacercariae of eight species of microphallid trematode, the rhizocephalan barnacles Polyascus polygenea, Sacculina nigra and Sacculina senta, and the obligate gut-inhabiting mesomycetozoan Enteromyces callianassae (potential parasite). The following have been identified in four of the other eight Pacific crabs within the genus (Hemigrapsus nudus and Hemigrapsus oregonensis, northern hemisphere; Hemigrapsus crenulatus and Hemigrapsus sexdentatus, southern hemisphere), none of which have been geographically displaced: metacercariae of two microphallid trematodes; cystacanths of three acanthocephalans Profilicollis antarcticus, Profilicollis botulus and Profilicollis novaezelandensis; larval nematode Ascarophis sp.; nematomorph Nectonema zealandica; entoniscid isopod Portunion conformis; mesomycetozoan Taeniella carcini; and nemertean egg predator Carcinonemertes epialti. The likelihood of the displaced species of shore crabs being rejoined with their native parasites or their susceptibility to becoming infected by similar parasites in their new locations is discussed. In future global displacements of parasitized Hemigrapsus species it is possible that their most serious parasites, rhizocephalans and entoniscid isopods, may infect previously uninfected species. For example, the two eastern Pacific species of Hemigrapsus (H. nudus and H. oregonensis) may be vulnerable to the rhizocephalans and may in turn be a source of entoniscids transported elsewhere.     

Comparative population biology of Uca rapax (Smith, 1870) (Brachyura,Ocypodidae) from two subtropical mangrove habitats on the Brazilian coast

The structure of two populations of the fiddler crab Uca rapax in two subtropical mangrove habitats near Ubatuba, State of São Paulo, Brazil were compared. The size–frequency distribution, sex ratio, and recruitment were evaluated. Sampling was performed monthly from April 2001 to March 2002 in the Itamambuca and Ubatumirim habitats. Crabs were caught manually for 15?min by two collectors during low tide. The carapace width of each crab was measured with a digital caliper, and the sex and ovigerous state were recorded. The median size of the carapace width of males was greater than that of females at both sites (P<0.05). The median size of the crabs from Itamambuca was larger than at Ubatumirim (P<0.05). Only 28 ovigerous females were obtained from both mangroves, which suggested that females might remain in their burrows during the incubation period. The highest recruitment pulse occurred in winter for both populations, probably as a consequence of high reproductive activity during summer. The sex ratio in the size classes showed an anomalous pattern, with a higher frequency of females in the intermediate size classes. This may be related to a greater energy requirement for reproduction in females, thus delaying growth. The variable environmental conditions to which Uca rapax populations are subject appear to act directly or indirectly on the population, causing variations in growth and reproductive processes in the different populations investigated here.     

The occurrence,mechanics and significance of burying behaviour in crabs (Crustacea: Brachyura)

Although the terms burrowing and burying are often used interchangeably in the literature, there are clear distinctions between these two types of behaviour in terms of their ecological, mechanical and physiological implications. Both types of behaviour are widely observed in the Brachyura. In comparison to the well researched area of burrowing in crabs, information on burying is relatively dispersed. This review will examine the extent of burying behaviour in brachyurans, and the physiological and ecological consequences of the behaviour within the group. At least nine of the 50 families of brachyuran crabs have either been observed to bury in soft substrata or are suspected, on morphological grounds, of burying. There appears to be no specific morphological adaptations for burying in brachyurans, apart from those features associated with respiration whilst buried in the sediment. Buried individuals must ensure constant access to oxygenated water in the face of mechanical problems resulting from direct contact with the sediment, i.e., the threat of clogging. Burying taxa deal with this challenge through accessory respiratory channels and altered respiratory rhythms. The evolutionary implication of the burying habit is equivocal. Burying taxa are amongst the most speciose and numerically dominant brachyuran groups in marine systems, all reaching their greatest diversity and abundance in soft substrata. Burying may be an ancestral condition, with many of these groups evolving in habitats characterized by soft sediment.     

Notes on Geryon tridens (Decapoda,Brachyura) from west of Ireland

Summary

One hundred and eighty males and 23 female specimens of Geryon tridens from 60 to 110 miles west of Ireland were examined in July 1968.

The carapace length/width relationship was calculated as;

and

where y = carapace length and x = carapace width.

Eleven per cent of the males captured had moulted recently, and one female had recently carried eggs.

The average size of crabs was found to increase from east to west, and it is suggested that the present sample is taken from the western side of the main population. There was no relationship between average size and the depth of the water in which they were caught.     

A new species of the genus Nanosesarma (Crustacea: Decapoda: Brachyura: Sesarmidae), and redescription of Nanosesarma jousseaumei (Nobili, 1906), including new records from the Persian Gulf

A new species of sesarmid crab from the Persian Gulf, Nanosesarma sarii n. sp. is described. Further, a poorly known species, N. jousseaumei (Nobili, 1906 Nobili, G. 1906. Faune carcinologique de la Mer Rouge. Décapodes et Stomatopodes. Ann Sci Nat, Zool ser. 9., 4(1): 1–347.  [Google Scholar]), is recorded from the Persian Gulf and recognized as a valid species. N. sarii n. sp. is allied to N. minutum (De Man, 1887) and N. jousseaumei (Nobili, 1906) Nobili, G. 1906. Faune carcinologique de la Mer Rouge. Décapodes et Stomatopodes. Ann Sci Nat, Zool ser. 9., 4(1): 1–347.  [Google Scholar], but is easily distinguishable from them through a number of characters, in particular the upper surface of the palm with a longitudinal granular ridge, the upper surface of the movable finger fully covered with tubercles, and abdomen of the male with the sixth segment wide and the seventh segment remarkably elongate. N. jousseaumei differs from its remaining congeners in having a large gap between the cheliped fingers, a large tubercle proximally on the outer surface of the movable finger, and large teeth on the posterior margin of the merus of the walking legs.