Nembrotha rutilans & Favorinus tsuruganus

December 30, 2002
From: Mark Burnett


Hi Bill,
I've been an avid reader of your site for some time. This is the first time I've sent anything in. In October a friend and I did a trip to Mabul, Borneo and had 10 wonderful days diving and photographing everything in site. On returning to New Zealand I found that my 13 species of nudibranchs photographed became 14. These slides of Nembrotha rutilans on an ascidian showed a much smaller nudibranch I couldn't identify. Doesn't appear in Debelius' book and it was not until I got a copy of Neville Coleman's 1001 Nudibranchs that I identified it as Favorinus tsuruganus. From your site I see it has been found in New Zealand. If it tends to favour Hexabranchus sanguineus eggs I wonder what species' eggs it feeds on here in NZ?
Mark Burnett

mburnett@actrix.gen.nz

Dear Mark,
Glad to get your first message, and look forward to many more. It's certainly interesting what things you can find when you look closely at your photos. While in tropical waters Favorinus tsuruganus is often found on the eggs of Hexabranchus, there is no good study to show that it doesn't also feed on less conspicuous egg ribbons. I suspect our eyes are attracted to the spectacular Hexabranchus eggs, which are often deposited in very open positions, and we don't look at the many smaller inconspicuous egg ribbons which are often deposited in crevices or under rocks. As David Harasti's message records, F. tsuruganus is found not uncommonly in the temperate waters of New South Wales, in eastern Australia. As in New Zealand, this is not Hexabranchus territory, so I suspect F. tsuruganus will feed on other eggs. As I discuss in the species' Fact Sheet, this is one species of Favorinus in which the colour of the ceratal digestive gland is independent of the colour of the eggs it eats.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Dec 30). Comment on Nembrotha rutilans & Favorinus tsuruganus by Mark Burnett. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/8743

Factsheet

Favorinus tsuruganus

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