Dendrodoris

Abstract: Maximum-parsimony analysis of the nucleotide sequence of the 16S mtDNA gene, obtained from several dorid nudibranch taxa, suggests that the radula-less dorids are likely to be a monophyletic group. However, there is little support for the most basal branches of the radula-less dorid clade. Most of the traditional groups within the radula-less dorids are monophyletic and for the most part well supported. These include the genera Dendrodoris, Doriopsilla, Reticulidia, Phyllidiella and Phyllidia (when Fryeria is included in Phyllidia). On the contrary, the family Dendrodorididae and the genus Phyllidiopsis are paraphyletic. Branch support for those arrangements that differ from the topology of previously published morphological trees is poor. Data obtained from the 16S mtDNA gene seem to be adequate to resolve the phylogenetic relationships of derived clades of radula-less dorids, but longer sequences are necessary to obtain more information at the most basal nodes.

Abstract: The 1996 Chagos expedition collected 128 specimens of opisthobranch gastropods representing at least 50 species, of which only 41 species are described in this paper: two cephalaspideans both belonging to the genus Chelidonura, two sacoglossan species of Thuridilla, one sea hare with problematic taxonomy, and 36 species of nudibranchs. Of the nudibranchs, all the sub-orders are represented by one or two species only except the dorids, which comprise the majority of the collection. Two species are allocated to genus only, one species each of Phyllidiopsis and Dermatobranchus, while two species are similar to known species. Numerous species of Phyllidiidae were collected, but only 10 are confidently assigned to a taxon. The taxonomic identities of Hoplodoris pustulata, Dendrodoris tuberculosa, Phyllidiopsis xishaensis and Phyllidiella striata are defined and discussed. There are four new distribution records for the Indian Ocean and several species are of interest as they have been rarely recorded.

Abstract: The histology of the major organ systems (digestive, reproductive, nervous, circulatory, excretory and respiratory, as wdl as epidermis) of the nudibranch Dendrodoris nigra (Stimpson, 1855) arc described for the first time and the results are compared with those derived from other members of the Doridoidea. It is shown that some characters which have been used to differentiate the genus Dendrodoris Ehrenberg, 1831 from other doridoideans (i.e., retractability of gills, lack of hard structures in the anterior digestive system, presence of pericardial glands) are problematic when used for phylogenetic ,analysis. This is especially true when taking into consideration that little is known about details of these structures in the Doridoide, as a whole.