Phylum Cnidaria is an ancient venomous group defined by the presence of cnidae, specialised organelles that serve as venom delivery systems. The distribution of cnidae across the body plan is linked to regionalisation of venom production, with tissue-specific venom composition observed in multiple actiniarian species. In this study, we assess whether morphological variants of tentacles are associated with distinct toxin expression profiles and investigate the functional significance of specialised tentacular structures. Using five sea anemone species, we analysed differential expression of toxin-like transcripts and found that expression levels differ significantly across tentacular structures when substantial morphological variation is present. Therefore, the differential expression of toxin genes is associated with morphological variation of tentacular structures in a tissue-specific manner. Furthermore, the unique toxin profile of spherical tentacular structures in families Aliciidae and Thalassianthidae indicate that vesicles and nematospheres may function to protect branched structures that host a large number of photosynthetic symbionts. Thus, hosting zooxanthellae may account for the tentacle-specific toxin expression profiles observed in the current study. Overall, specialised tentacular structures serve unique ecological roles and, in order to fulfil their functions, they possess distinct venom cocktails.

The role of insulin and insulin-like peptides (ILPs) in vertebrate animals is well studied. Numerous ILPs are also found in invertebrates, although there is uncertainty as to the function and role of many of these peptides. We have identified transcripts with similarity to the insulin family in the tentacle transcriptomes of the sea anemone Oulactis sp. (Actiniaria: Actiniidae). The translated transcripts showed that these insulin-like peptides have highly conserved A- and B-chains among individuals of this species, as well as other Anthozoa. An Oulactis sp. ILP sequence (IlO1_i1) was synthesized using Fmoc solid-phase peptide synthesis of the individual chains, followed by regioselective disulfide bond formation of the intra-A and two interchain disulfide bonds. Bioactivity studies of IlO1_i1 were conducted on human insulin and insulin-like growth factor receptors, and on voltage-gated potassium, sodium, and calcium channels. IlO1_i1 did not bind to the insulin or insulin-like growth factor receptors, but showed weak activity against K_V1.2, 1.3, 3.1, and 11.1 (hERG) channels, as well as Na_V1.4 channels. Further functional studies are required to determine the role of this peptide in the sea anemone.

The taxonomy of soft corals with a stoloniferous growth form is challenging. The family Clavulariidae and, more specifically, the genus Clavularia have acted as a repository for most stoloniferous corals that could not systematically be differentiated with morphology. In addition, the lack of morphological and genetic data for the type species of Clavularia, Clavularia viridis, has made a revision of the genus impossible. In this study, we use an integrative taxonomic approach combining morphological examinations and novel molecular methods to revise the taxonomy and systematics of Clavulariidae within Octocorallia. We re-describe key species of Clavularia, including C. viridis, C. inflata and C. koellikeri, resolve the position of Clavulariidae within Octocorallia, and present a revised taxonomy of the tropical, zooxanthellate species of Clavularia that includes morphological characters of each species. We further confirm the polyphyly of Clavulariidae, and resurrect the genus Hicksonia and family Hicksoniidae (Malacalcyonacea) to accommodate a new species with connecting tubes on multiple levels (H. tohrui sp. nov.). We also describe a new genus and species of Clavulariidae from Japan Bairdium iriomotejimaensis gen. nov., sp. nov. and a new Clavularia species from the Great Barrier Reef (C. brunafolia sp. nov.). This study resolves the fundamental taxonomy of Clavularia, and provides the necessary baseline for future works. ZooBank: urn:lsid:zoobank.org:pub:61754CF6-A3C9-4D1C-AC6F-4435C12BD4AD