86 — Gem nudibranch, Dendrodoris krusensternii

The gem nudibranch (Dendrodoris krusensternii (Gray, 1850)) is found throughout the warm temperate Indo-west Pacific. In New Zealand waters they are found in the northern parts of North Island. They live in shallow water, from low tide down to a few metres and can reach ~90mm in length.

They can be be quite spectacular in colour, with small diamond-shaped patches of bright iridescent blue (sadly missing from the individual pictured below). However, they are also very variable, both in colour and morphology, so they have been given several names over the years. They have suctorial mouth parts and closely related species feed on sponges, but their diet remains little understood.

Nudibranchs have evolved to be shell-less, so they lack the primary protection a shell provides. Therefore they have developed chemical defences to render them unpalatable or toxic to potential predators. Some New Zealand nudibranchs (e.g., Tambja spp.) have the ability to sequester toxins from their prey (to use for chemical defence). However, Dendrodoris denisoni can biosynthesize its own. Being able to do this is an advantage, as it means that the slug not tied to a particular food for the source of its chemical defences.

Dendrodoris krusensternii, Pilot Bay,
Mt. Maunganui, 16/11/16.

Dendrodoris krusensternii, Pilot Bay,
Mt. Maunganui, 16/11/16.

More info:


Grkovic, Appleton, DR, Copp BR, 2005. Chemistry and chemical ecology of some of the common opisthobranch molluscs found on the shores of NE New Zealand. Chemistry in New Zealand. Dec. 12–15.


http://www.seaslugforum.net/find/denddeni

Willan, R.C.; Morton, J.E. 1984. Marine Molluscs Part 2: Opisthobranchia. University of Auckland, Leigh Marine Laboratory, Leigh, New Zealand. 106 Pp.