Re: Okinawa Placida sp.?

March 22, 2005
From: Cynthia Trowbridge

Dear Bill, Kathe, and Bob,
I have been reading messages you wrote several years ago about the problem or challenge of 'Placida dendritica' from Okinawa [#7277, #7329 ].

I have been working with Yoshiaki and Yayoi Hirano and their students (Chiba University) for several years. We have just completed our 6th sacoglossan survey of Okinawa and I venture to comment on some of the 'Placida dendritica' (in the broadest sense) species found in Okinawa.

Locality: west coast of Okinawajima, Okinawa, Japan, East China Sea. Depth: 1 m . Length: several mm (data in Japan). 10-15 March 2005. rocky intertidal or shallow subtidal. Photographer: Tomohiro Watanabe.

I agree with Kathe's statement [#4177] that the French Polynesian 'Placida dendritica' really belong to Ercolania. This species (or a sibling one) is very common in Okinawa but I will present details about it separately.

Next, there are two species (?) of 'Placida' associated with Codium in Okinawa. The first is very, very, very common: we have collected hundreds on Codium intricatum and some on the coexisting C. arabicum. They were on Codium during every one of our 6 trips -- thus, this species appears to be present all year around. The radular teeth are blade-shaped but I have not looked at the reproductive system yet. I have started sequencing the COI gene of this animal. I think that this species may be what Kathe was calling Stiliger / Placida verticillata....? [Photos: A, B ]. I would be eager to hear others' views.

The second form or species (?) is much less common [Photo: C]. We have only collected 2 individuals of this from Codium (March 2005). This animal looks much more like what Baba (1986) called Placida sp. (=Hermaea dendritica). It has shorter rhinophores that flare a bit terminally. It looks much more like the Placida sp. (sensu Baba 1986) that we find in Sagami Bay.

  • Baba K (1986) Anatomical information on Placida sp. = Hermaea dendritica of Baba, 1937 and 1955, from Japan. Shells and Sea Life 18:21-22

Finally, we have yet another Placida species associated with Bryopsis from Okinawa and Izu Peninsula. I will present that species separately.

I would be keen to hear what you think about these sacoglossans.


Trowbridge, C.D., 2005 (Mar 22) Re: Okinawa Placida sp.?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Cynthia,
I think I will leave this for Kathe to comment on
Best wishes,
Bill Rudman

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