Distribution of Defensive Metabolites in Nudibranch Molluscs

Abstract

Many plants and animals store toxic or unpalatable compounds in tissues that are easily encountered by predators during attack. Defensive compounds can be produced de novo, or obtained from dietary sources and stored directly without selection or modification, or can be selectively sequestered or biotransformed. Storage strategies should be optimized to produce effective defence mechanisms but also prevent autotoxicity of the host. Nudibranch molluscs utilize a diverse range of chemical defences, and we investigated the accumulation and distribution of defensive secondary metabolites in body tissues of 19 species of Chromodorididae nudibranchs. We report different patterns of distribution across tissues, where: 1) the mantle had more or different (but structurally related) compounds than the viscera; 2) all compounds in the mantle were also in the viscera; and 3) the mantle had fewer compounds than the viscera. We found no further examples of species that selectively store a single compound, previously reported in Chromodoris species. Consistent with other studies, we found high concentrations of metabolites in mantle rim tissues compared to the viscera. Using bioassays, compounds in the mantle were more toxic than compounds found in the viscera for Glossodoris vespa Rudman, 1990 and Ceratosoma brevicaudatum Abraham, 1876. In G. vespa, compounds in the mantle were also more unpalatable to palaemonid shrimp than compounds found in the viscera. This indicates that these species may modify compounds to increase bioactivity for defensive purposes and/or selectively store more toxic compounds. We highlight clear differences in the storage of sequestered chemical defences, which may have important implications for species to employ effective defences against a range of predators.

Uncovering the core microbiome and distributions of palmerolide inSynoicum adareanumacross the Anvers Island archipelago, Antarctica

“…For example, nudibranchs sequester toxic compounds, which have been biosynthesized by the gastropod or acquired from their prey. The toxins are concentrated in the anatomical space of their mantles, the most vulnerable portion of their soft, exposed bodies (52–54). Bioaccumulation of secondary metabolites in invertebrates with less anatomical differentiation is also known to occur.…”

Terpenoids in Marine Heterobranch Molluscs

“…The same study reports that Chromodoris splendida from Australia presents aplysulphurin (61) (Figure 8), probably from its diet, the demosponge Darwinella tango, together with gracilin metabolites, such as gracilin C 20, not found in the sponge. A recent study on 19 species of Chromodoridid nudibranchs from Australia, mentioned above, reported many diterpenoids, among other compounds, found in mantle and internal glands [154]. In that work, mixtures of compounds are described in Goniobranchus nudibranchs, containing spongian diterpenes, norditerpenes, and rearranged diterpenes.…”

“…Although a defensive role is highly probable, it remains to be further proved using sympatric predators [46,153]. Recently, a study on 19 species of Chromodorididae nudibranchs from Australia reported 72 compounds, including many bicyclic furanosesquiterpenoids, among others, found in mantle and internal glands [154]. In particular, Mexichromis festiva contains euryfuran and dendrolasin, while M. mariei only possesses euryfuran.…”

“…Among the sea slugs, the chromodorid nudibranch Goniobranchus splendidus from Australia presents 31 different terpenes, including the linear furanoditerpene ambliofuran (39) ( Figure 6) [154], while Chromodoris reticulata (also from Australia) presents this compound in its viscera [175].…”

Recent advances in allelopathy for weed control: from knowledge to applications

“…Sesquiterpenes are C‐15 terpenoids that are classed as secondary metabolites with an extensive range of biological properties such as antifeedant, antibacterial and antifungal activities. Sesquiterpenes have defensive roles in plants .…”