Coral reef is one of the prominent habitats in Taiwan where sea slugs are common inhabitants. However, research on sea slug in Taiwan still remains deficient. Between June 2004 and May 2006, surveys on the western coast of the Kengting Peninsula, the northeastern coast of Taiwan, Lan Yu, Green Island, Liuchiu Island, and Penghu were conducted for sea slugs. In total, 4 suborders, 14 families, and 105 species were recorded; 85 species were new records, and 6 were possible new species. Among these 105 species, specimens of 44 species in 8 families were available for investigation of spicule morphology which has been considered as an uninformative taxonomic character. Five types of spicules were recognizable in which the spindle-like type had broadest distribution among the species and is considered as the plesiomorphic character state. A possible autapomorphic type was found in Phyllidiella pustulosa; this status can be ensured until spicules of other congeners are known. Distribution of the other two spciule types provided information for a hypothesis for the family phylogenetic interrelationship which shows certain agreement with existing phylogenetic hypotheses. In Dorididae and Chromordorididae, distribution of the spicule types showed no spatial discrepancy in the whole animal, whereas such discrepancy pertained in Phyllidiidae. More information on spcicule morphology are needed before their taxonomic importance can be justified.

The marine realm and, in particular, the Antarctic benthos is largely unexplored and understudied. The chemical investigation reported herein reveals not only the biodiversity, but how that biodiversity manifests remarkable chemical diversity. In our continuing study of the nudibranch Austrodoris kerguelenensis, we have isolated a diverse suite of diterpenoid glyceride esters, palmadorins D - S (2.32 - 2.47), one of which is the first reported halogenated diterpene from a dorid nudibranch. Utilizing genomic data from collaborators, we have investigated the chemical diversity from phylogenetically unique specimens collected in close proximity to one another. Chemical groupings based on comparison of LC/MS metabolite fingerprints from individual organisms correlated well to the genetic data. Our research shows that A. kerguelenensis specimens from the same phylogroups elaborate near identical metabolite profiles to each other, but distinct from other phylogroups. Dendrilla membranosa is a dominant demosponge that prior studies have shown is rarely preyed upon and deters feeding against amphipods, the principal mesograzers of the Western Antarctic Peninsula. To assess the defensive nature of the pure compounds, artificial food pellets spiked with membranolides were evaluated in a feeding assay against the omnivorous amphipod Gondogeneia antarctica whereby only artificial pellets containing membranolide exhibited significant feeding deterrence. The research reported herein demonstrates that membranolides C and D were originally misassigned. Reevaluation of new extracts evolved additional fused furan membranolides G and H, and allowed for complete characterization of the four epimers. Extraction of sponge in CD3OD resulted in incorporation of a deuterated methyl group into fragment ions as evidenced from LC/MS chromatograms. Further chemical investigation of D. membranosa without the use of methanol revealed that these non-natural products arise from aplysulphurin, a known compound originally isolated from the sponge Aplysilla sulphurea, but later isolated from D. membranosa. These studies emphasize the importance of exploring the marine realm for the presence of antiviral compounds, not only for identification of small molecules but also as a source of potent macromolecules. Subfractions from Gigartina skottsbergii possesses strong anti-influenza activity toward both the A/Wyoming/03/2003 (H3N2) and A/California/04/2009 (H1N1) virus with EC50 values in the range of 5 to 10 μg/mL. The virus-inhibitory effect was selective, dose-dependent, strain-specific and the virus induced cytopathogenic effect (CPE) was reduced at non-toxic concentrations of the extract.

Synoicum adareanum is a colonial tunicate commonly found on the benthos around Palmer Station on Anvers Island, Antarctica. A comprehensive chemical investigation of the lipophilic extract of the frozen tunicates gave a new series of polyketide macrolides, palmerolides A-E and H. The structure elucidation of these compounds was accomplished by extensive NMR and mass spectral studies.The palmerolides are unusual 20-membered macrolides displaying functionality more commonly found in sponges or cyanobacteria. Palmerolide A, the major member of the group, shows significant and selective in vitro cytotoxicity against melanoma with three orders of greater sensitivity relative to other cell lines tested, in the National Cancer Institute (NCI) 60 human cancer cell-line panel. In addition, it displays potent cytostatic activity against several other cancer cell lines. Based on NCI's COMPARE analysis, palmerolide A was investigated as a V-ATPase inhibitor and shown to bind the V0 subunit with 2 nM inhibition.Austrodoris kerguelenensis is a common Antarctic nudibranch widely distributed in the High Antarctic and Sub Antarctic Zone. It is characterized by the presence of terpenoid glyceryl esters which are supposed to be involved in defense. Chemical investigations of several specimens of A. kerguelenensis collected near Palmer station Antarctica afforded hitherto undescribed series of clerodane diterpenoid glycerides. The structure elucidation of three major compounds of this series, palmadorin A, B and C was accomplished.

In the Indian River Lagoon, the nudibranch Okenia zoobotryon and its egg masses are found attached to the bryozoan Zoobotryon verticillatum throughout the year. Okenia zoobotryon is thought to live, feed, and reproduce exclusively on Z. verticillatum, which would make this a very specialized predator-prey interaction. The primary goal of my study was to document certain aspects of the ecological and chemical relationships between Z. verticillatum and O. zoobotryon. Specifically, I wanted to understand the cues used by the nudibranch to locate and remain on Z. verticillatum. Population surveys on Z. verticillatum, as well as other potential hosts, were performed. From these surveys, I found a small number of O. zoobotryon adults and egg masses on the red macroalga S. filamentosa mixed with Z. verticillatum (0.01 and 0.05 g/wet-weight, respectively), none on the bryozoan Amathia distans, and none on the red macroalga Gracilaria tikvahiae. To determine if prey identification was associated with an adult cue, I ran paired-choice trials. In these, the adults did not significantly prefer Z. verticillatum. Next, laboratory culture of larvae of O. zoobotryon was performed. During larval culture some aspects of this previously undocumented life-history were recorded; adults of this species developed from planktotrophic veliger larvae that hatched out of egg masses between 4 and 6 days, the time post-hatching to settlement was 7-8 days, and metamorphosis occurred approximately 24 hours after settlement. The final question addressed in this study was; "Does O. zoobotryon feed on and take up chemicals from Z. verticillatum?" To address this question, high-performance liquid chromatography was performed on extracts of Z. verticillatum and O. zoobotryon. Both organisms were compared and found to contain similar compounds, which suggest that the nudibranch is feeding on Z. verticillatum and taking up chemicals. Concentrations of compounds in Z. verticillatum varied between populations in the northern and southern regions of the Indian River Lagoon. There are, also, differences between the chemical composition of Z. verticillatum in the IRL (northern and southern) and the California species identified by Sato and Fenical (1983).

These studies compare neurotransmitter localization and the behavioral functions of homologous neurons in nudibranch molluscs to determine the types of changes that might underlie the evolution of species-specific behaviors. Serotonin (5-HT) immunohistochemistry in eleven nudibranch species indicated that certain groups of 5 HT-immunoreactive neurons, such as the Cerebral Serotonergic Posterior (CeSP) cluster, are present in all species. However, the locations and numbers of many other 5 HT-immunoreactive neurons were variable. Thus, particular parts of the serotonergic system have changed during the evolution of nudibranchs. To test whether the functions of homologous neurons are phylogenetically variable, comparisons were made in species with divergent behaviors. In Tritonia diomedea, which crawls and also swims via dorsal-ventral body flexions, the CeSP cluster includes the Dorsal Swim Interneurons (DSIs). It was previously shown that the DSIs are members of the swim central pattern generator (CPG); they are rhythmically active during swimming and, along with their neurotransmitter 5-HT, are necessary and sufficient for swimming. It was also known that the DSIs excite efferent neurons used in crawling. DSI homologues, the CeSP-A neurons, were identified in six species that do not exhibit dorsal-ventral swimming. Many physiological characteristics, including excitation of putative crawling neurons were conserved, but the CeSP A neurons were not rhythmically active in any of the six species. In the lateral flexion swimmer, Melibe leonina, the CeSP-A neurons and 5-HT, were sufficient, but not necessary, for swimming. Thus, homologous neurons, and their neurotransmitter, have functionally diverged in species with different behaviors. Homologous neurons in species with similar behaviors also exhibited functional divergence. Like Melibe, Dendronotus iris is a lateral flexion swimmer. Swim interneuron 1 (Si1) is in the Melibe swim CPG. However, its putative homologue in Dendronotus, the Cerebral Posterior ipsilateral Pedal (CPiP) neuron, was not rhythmically active during swim-like motor patterns, but could initiate such a motor pattern. Together, these studies suggest that neurons have changed their functional relationships to neural circuits during the evolution of species-specific behaviors and have functionally diverged even in species that exhibit similar behaviors.

Chemosensation is achieved through the binding of chemical signals to chemoreceptor proteins embedded in the membranes of sensory neurons. The molecular identity of these receptors, as well as the downstream processing of chemosensory signals, has been well studied in arthropods and vertebrates. However, very little is known about molluscan chemosensation. The identity of chemoreceptor proteins in the nudibranch mollusc Berghia stephanieae are unknown. Data from other protostome and molluscan studies suggest Berghia may use ionotropic receptors for some forms of chemoreception. This study used a bioinformatics approach to identify potential chemosensory ionotropic receptors in the transcriptome of Berghia. A hidden Markov model program was used to generate molecular profiles of previously identified chemosensory receptors in other animals. A Berghia transcriptome was then searched for likely homologous sequences. Candidate sequences were investigated using protein prediction tools and molecular phylogenies. Fourteen ionotropic glutamate receptors (likely synaptic) and five divergent ionotropic receptors were identified. One of these divergent ionotropic receptor sequences, IR-D, may encode a chemosensory receptor and was therefore selected to determine its cellular expression in sensory and brain tissue using in situ hybridization chain reaction. Expression was seen in the rhinophores and oral tentacles of Berghia, as well as in the rhinophore ganglion, cerebral-pleural ganglion, and pedal ganglion. Similar expression patterns were obtained with tissue-specific transcriptomic data. This was the first study to investigate IR-D as a potential chemosensory receptor in molluscs, and thus has helped identify a new family of possible ionotropic chemoreceptor proteins in molluscs. These results have laid the groundwork for continued investigation of Berghia’s chemosensory system.