New species and records of Asellota from the Indian Ocean (Crustacea: Peracarida: Isopoda)

In this study of asellote Isopoda from the Indian Ocean, 29 species in 11 genera and seven families are recorded. Twenty-one species are described as new: family Gnathostenetroididae, Maresiella aldabrana ; family Janiridae, Carpias mossambica ; family Joeropsidae, Joeropsis algensis, J. arpedes, J. dimorpha, J. hamatilis, J. lentigo, J. pentagona, J. pleurion ; family Pleurocopidae, Pleurocope wilsoni ; family Pseudojaniridae, Pseudojanira meganesus ; family Santiidae, Santia spicata, S. urospinosa ; family Stenetriidae, Hansenium aldabrae, H. expansa, H. remocarpus ; Mizothenar serratum, Stenetrium assumentum, S. quinquedens, S. zanzibarica, Stenobermuda brucei. The first record of the family Pleurocopidae (Pleurocope wilsoni) and the genus Mizothenar (family Stenetriidae) from the Indian Ocean are included. Diagnoses of the genera and species are provided, and keys to the Indian Ocean species of most of the genera. The material comes primarily from Aldabra Atoll, the granitic Seychelles islands, Zanzibar Island, the Comoro Islands, and Phuket in Thailand. A few samples are from material of the International Indian Ocean Expedition carried out in the mid-1960s.     

A revision of Heterosignum (Asellota,Isopoda, Paramunnidae) with descriptions of three new species

Three new species of Heterosignum are described from Japan. Heterosignum elegans sp. nov. differs from its congeners in having stout preorbital lobes on the head, very long lateral spine-like processes and eyestalks, and very long article 2 of male pleopod 2. Heterosignum ohtsukai sp. nov. is distinctive in having a marked stout mid-dorsal spine on the head, long mid-dorsal spines on the pereonites, and article 2 of antenna 1 with a distolateral protrusion. Heterosignum otsuchiensis sp. nov. has single lateral spine-like processes on pereonites 1-7 as in H. ohtsukai, but is distinguished from it in having short mid-dorsal spines on pereonites 1-7 and long basis of pereopod 1. Heterosignum mutsuensis Gamô, 1976 is redescribed using newly collected specimens. Coulmannia unicornis Kensley, 1976 is assigned to Heterosignum after careful examination of the types. The diagnosis of Heterosignum is emended to include all the five species so far recorded.     

Seasonal reproduction in deep-sea Crustacea (Isopoda: Asellota)

A collection of Crustacea Isopoda (suborder Asellota) from a 10-year sampling programme in the Rockall Trough, NE Atlantic (54°40′N, 12°15′W) was analysed for evidence of breeding seasonality. No evidence of seasonal activity was found — adults and newly released juveniles were present throughout the year — but there was a strong seasonal pattern for breeding intensity. A significantly higher proportion of females was brooding during the winter months (25%) compared to the summer (5%), and the percentage of females brooding varied significantly with depth. The breeding pattern was synchronized to the seasonal deposition of organic detritus known to occur during the summer in the NE Atlantic. There were more newly released juveniles in samples during the summer than during the winter, with most females appearing to release their young at the time the deposition began. This deposition appears to be a major seasonal factor dominating the life-cycles of most benthic species in the Rockall Trough. Juvenile settlement for a range of taxa (echinoderms, molluscs and crustaceans) occurs while the detritus is present and most species maximize vitellogenesis at this time.