Hypselodoris bennetti (Angas, 1864)
Occasionally extremely common throughout the Solitary Islands Marine Park. Only known from the east coast of Australia, most records in New South Wales.
Found in shallow to deep rocky reef.
Bright to darker blue body, with pale red tinged gills and rhinophores. The mantle has a yellow border with a row of red spots on the inner side. Often found in pairs, see mating couple in top photograph, is diurnally active and grows to 60 mm, although is usually smaller. Its food sponge is Psammocinia sp. which is often overgrown with algae and not easily recognisable. Similar Goniobranchus hunterae has pale gills and rhinophores.
Gary Cobb, David Mullins, Nudibranchs Encyclopedia, 2nd Edition, 2015. Publishers Thomas Slone, Masalai Press and Tim Hochgrebe, Underwater Australasia. p.142.
Australian Museum, Sea Slug Forum. http://www.seaslugforum.net/find/hypsbenn. Accessed 24/09/2018.