Costasiella from the Philippines

May 15, 2002
From: Erwin Koehler

Dear Bill,
Concerning the possible Costasiella. Here is a shot by Klaus Stark [email]) showing both animals together. I hope you can see the eyes good enough.


Koehler, E., 2002 (May 15) Costasiella from the Philippines. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Note: Moved to Costasiella sp. 3. See relevant message. - 2 April 2003

Thanks Erwin,
Yes the eyes are clearly those of a Costasiella. It is possibly Costasiella kuroshimae Ichikawa 1993 but unfortunately the description is not detailed enough to be sure. We have no idea of how variable species of Costasiella are in colour so it is impossible to know whether differences between this animal and the original description are intra-specific or inter-specific.

Costasiella kuroshimae was described as having a white head with dark marks in the midline and a dark streak across the head just in front of the rhinophores. Also a dark grey-black streak behind the eyes in dorsal midline was described. The tips of the white rhinophores were reported to be black, but in Ichikawa's drawing the black did not extend halfway down as in these photos. The cerata were described as 'generally green with white tips'. Ichikawa described a number of species of Costasiella in a similar brief fashion. Of all the species described, this is the only one that come near to these photos.

• Ichikawa, M. (1993) Saccoglossa (Opisthobranchia) from the Ryukyu Islands. Publications of the Seto Marine Biological Laboratory, 36: 119-139.

Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 15). Comment on Costasiella from the Philippines by Erwin Koehler. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Costasiella sp. 3

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