Costasiella ocellifera? from Okinawa

November 29, 2006
From: Robert F. Bolland

Concerning message #18452:

Hi Bill,
Here's another Costasiella from Okinawa, similar to Atsushi Ono's animal on a recent Forum post.
Data: RFB #3585-C / TL: 4mm / 55m / Seragaki, Okinawa / 4 May 1997
RFB #3884-B / TL: 2~5mm / 55m / Seragaki, Okinawa / 8 August 2001
I've collect sixteen of these, specimens deposited with Terry Gosliner at CAS.

Locality: Seragaki, 180ft (55m), Okinawa, Japan, Pacific, 4 May, 1997 / 8 August, 2001, mixed coral rubble and sand with numerous thallophytes. Length: 2~5mm. Photographer: R. F. Bolland.


Bolland, R.F., 2006 (Nov 29) Costasiella ocellifera? from Okinawa . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Bob,
Thanks for these photos. They certainly clarify the picture - at least in my mind - and illustrate the confusion that can occur by naming new species on very little information. Your animals seem to fit the description of Costasiella vegae Ichikawa 1993.

The most distinctive feature of C. vegae seems to be the eye spot on each cerata. However Ichikawa described the eyespots as being 'a whte spot encircled by a dark green ring'. In both your animals and Atsushi Ono's the spots are blue, and while the ones in your upper photo are surrounded by a dark green ring, the ring is absent in Atsushi Ono's, and your lower photo. Also Ichikawa describes a distinctive maek behind the eyes as 'a conspicuous red mark behind the eyes like a posteriorly pointing arrow head' which is not clear in the drawiing of the animal. I suspect the mark is the blue eye spot or mark found in your animals and Atsushi Ono's. Ichikawa also describes a red subapical band around the cerata. This is not visible in Atsushi Ono's or your animals but there is an orange subapical band around the cerata of C. ocellifera from the Caribbean. Ichikawa's description of  C. vegae was based on 6 specimens collected at the Ryukyu Islands on Avrainvillea. I suspect your animals and Atusushi Ono's are part of the colour variation of C. vegae. I also suspect that C. vegae is the same as the Caribbean C. ocellifera.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Nov 29). Comment on Costasiella ocellifera? from Okinawa by Robert F. Bolland. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Costasiella vegae

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