November 17, 2009
From: Gary Cobb
Concerning message #1000:
Hi Bill and everyone!
Well I see there has not been an entry for this species since 1999! Let the drought be over now. Aaron and I went to the Mooloolaba Rockwall Ledges dive and found a piece of hydroid with an egg mass on it. I gingerly plucked it off and put it in the collection jar.
Upon transferring everything to a white bowl I was pleasantly surprised to count 34 Doto rosacea, Polycera melanosticta, Polycera risbeci and Janolus mirabilis.
This is one mean slug! It constantly shakes its cerata when touched. It also forces its cerata forward and backward when it starts to crawl. Making it very hard to get a great photo!
The cerata are split into 2 groups, a smaller toward the posterior end. There are two large white blotches in front and behind the forward cerata group. The anterior cerata group also surrounds the rhinophores.
When at rest it resembles a small Furball!
Locality: Mooloolaba Rockwall Ledges, 3 m max depth, Queensland, Australia, Pacific Ocean, 08 November 2009, Subtidal. Length: 5 mm long. Photographer: David Mullins on microscope.
Cobb, G., 2009 (Nov 17) Janolus mirabilis found sthn Queensland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22768
Thanks for these photos of this strange animal. I suspect its apparent rarity is because of its size and cryptic colouration. It's surprising how a number of unrelated species have evolved this habit of rhythmically 'jerking' their cerata [see Limenandra nodosa, Aeolidiella alba].
Is it possible the hydroid you found it on may have been a mix of hydroid and branching bryozoan? Why I ask is that while Doto certainly feeds on hydroids, species of Janolus and Polycera are feeders on branching bryozoans.