Rediscovery of Runcinella zelandica

Dear Gareth,
This is a very interesting find. It is Runcinella zelandica and to my knowledge this is only the second time it has been reported alive. Your photos are the first coloured photos of living animals to be published. It was originally collected on a Swedish expedition in 1914-16 at Cape Brett, Bay of Islands (Odhner, 1924), from preserved animals, and its external colour was unknown until Willan, (1981) rediscovered it at the nearby Poor Knights Ids.

Two interesting features in your photos are the way the anterior corners of the head are folded into pseudo-tentacles and the relatively large gills which stick out behind the posterior mantle. These are not features which we could see from preserved animals.

I spent many hours trying to find live specimens of this animal as a graduate student. I was studying Runnica katipoides, the common intertidal runcinid in New Zealand, which at that time was misidentified as Runcinella zelandica simply because it was the only species known from New Zealand. When Michael C. Miller and I looked at its anatomy it was very clear that it was not Odhner's species so we named it Runnica katipoides. We would have liked to have had some specimens of true Runcinella zelandica for comparative purposes but neither I nor Michael Miller, who had been studying the NZ fauna for many years, had ever found it. If it is indeed restricted to northeastern New Zealand it is a very strange distribution, so it would be useful to look out for it in other parts of New Zealand just so we have better idea of its range.

Unfortunately I don't have a photo of Runnica katipoides so if anyone has one to share it would be nice to include in the Forum for comparative purposes. It is often very common in coralline algal turf both intertidally and in the shallow sublittoral. It is black with a red stripe down its back.

• Miller, M.C. & Rudman, W.B. (1968) Two new genera and species of the Superfamily Runcinoidea (Mollusca, Gastropoda, Opisthobranchia) from New Zealand. Transaction of the Royal Society of New Zealand (Zoology), 10(19): 183-9, 3 figs.
• Odhner, N.H. (1924) Papers from Dr. Th. Mortensen's Pacific expedition 1914-16. New Zealand Mollusca. Videnskabelige Meddeleser fra Danske Naturhistorisk Forening, 77: 1-90. (Pls.1-2)
• Willan, R.C. (1981) Rediscovery of Runcinella zelandica Odhner, 1924 (Opisthobranchia: Runcinacea). National Museum of New Zealand Records, 2(2): 5-8.

Best wishes,
Bill Rudman