Shireen Fahey

Geographic Variation of Natural Products of Tropical Nudibranch Asteronotus cespitosus

Extracts of the dorid nudibranch Asteronotus cespitosus from two geographically separate regions of Australia and from the Philippines were compared using thin-layer, high-performance liquid and gas chromatography and 1H NMR analysis. Halogenated metabolites were detected in all mollusk specimens. The major component detected in digestive tissue of specimens from the Great Barrier Reef in northeastern Australia was 4,6-dibromo-2-(2′,4′-dibromophenoxy)phenol (1), with minor amounts of 3,5-dibromo-2-(3′,5′-dibromo-2′-methoxyphenoxy)phenol (2). In a specimen collected from northwestern Australia, only 3,5-dibromo-2-(3′,5′-dibromo-2′-methoxyphenoxy)phenol was found. The specimen from the Philippines contained 2,3,4,5-tetrabromo-6-(2′-bromophenoxy)phenol (3) together with a novel chlorinated pyrrolidone (4). In addition, the sesquiterpenes dehydroherbadysidolide (5) and spirodysin (6) were detected in the digestive organs and mantle tissue of the nudibranchs from the Great Barrier Reef and from the Philippines, whereas these chemicals were not found in the specimen from northwestern Australia. All of the chemicals (1-3,5, and 6) have previously been isolated from the sponge Dysidea herbacea, as have chlorinated metabolites related to 4. This is the first time the characteristic halogenated metabolites that typify Dysidea herbacea have been reported from a carnivorous mollusk, which implies a dietary origin as opposed to de novo synthesis.

The phylogeny of Halgerda (Opisthobranchia, Nudibranchia) with the description of a new species from Okinawa

This paper proposes a refined hypothesis of evolution for the tropical Indo‐Pacific nudibranch genus Halgerda. Numerous specimens from 31 species were examined anatomically and literature from four additional species was reviewed, bringing to 33 the ingroup taxa. Fifty‐three characters were considered from these examinations. The outgroup Asteronotus was used to polarize the characters. The phylogeny obtained from the analysis of the characters supports the hypothesis that Halgerda is a monophyletic group. A species previously placed with the genus Sclerodoris is examined and determined to be a member of the genus Halgerda. Phylogenetic analysis places this species, H. paliensis, as a basal member of the genus.Halgerda paliensis appears to be restricted to the Hawaiian Islands. Specimens previously identified as Sclerodoris paliensis from the Marshall Islands actually represent H. dalanghita Fahey & Gosliner, 1999. A new species, Halgerda onna, is described and presented as the sister taxon to a basal member of the genus. A range and depth extension of a previously described species, H. malesso, is presented. The present phylogeny is then compared to previous studies, in particular those of Fahey & Gosliner (1999a,b) .