DIVE LOG AUSTRALASIA FEB 2026

how important chemicals are in their navigation of life. Many animals and plants that form the diet of sea slugs possess anti-feedant chemicals (secondary metabolites) in their tissues as a deterrent to predation. For the sea slugs to be able to consume food that contains these anti-feedants, without consequence, is certainly advantageous, as it provides access to a broader diet and there would be fewer competitors for the same resource. However, to take them up and repurpose them for self-defense lifts the capability to a whole other level. Source These defensive chemicals are transferred from the dietary intake of sea slugs to special storage formations, often referred to as mantle dermal glands , or they might be modified or even biosynthesized de novo and stored similarly, as it has been ascertained that those particular types are

not found and ingested through their diet. The method by which the specific defensive dietary chemicals are selected, separated and transported from the ingested material is currently unknown. As mentioned, many types of marine fauna contain what are referred to as anti-feedants or secondary metabolites – organic compounds that are produced but are not necessary for the normal functioning of the organism. Sponges, the diet of many of the dorid nudibranchs, are an excellent example. Sponges contain some of the most toxic chemical compounds to be found in nature. Some sponges should not even be handled without protective gloves. There are thought to be four sources of these compounds in a sponge – those produced by the sponge itself by its own metabolism, those produced by the microbes or bacteria hosted by the sponge (the number of bacterial cells in some sponges is calculated to be higher than their own cell count), those produced by the association

The spongivorous chromodorids predate upon a variety of sponges - some broadly, others quite specific. Clockwise from upper left: Goniobranchus splendidus is known to feed upon at least five species across the Darwinellidae family; Cadlinella ornatissima shows a marked level of non- specialisation by feeding across several sponge families; Goniobranchus collingwoodi on the other hand is restricted to the Dictyodendrilla genus; Goniobranchus fidelis, based on current records, appears to be restricted to Chelonaplysilla violacea. DIVE LOG Australasia #416 February ‘26 21 www.divelog.net.au