Bryozoan food of Okenia cf. hiroi from NZ
February 4, 2005
From: Dennis Gordon
Dear Bill
It's a nice pic! The dull red bryozoan that the slug appears to be feeding on, is indeed a eurystomellid. I think it is Eurystomella, not Integripelta, but I'm not sure. Eurystomella has large foramina in the calcareous frontal wall while Integripelta lacks them. They are not obvious in the photo but some zooids look like they could have them. There are 3 species of Eurystomella and 2 Integripelta known from New Zealand but the two species of Integripelta are known only from the Spirits Bay/Three Kings area in the far north.
The yellow bryozoan is problematic as the everted lophophores conceal the diagnostic zooidal skeletal features. The round white bryozoan is Disporella novaehollandiae (formerly Lichenopora novaezelandiae). I have no idea what the bright red bryozoan at the bottom of the photo is.
The fact that a local eurystomellid now has a confirmed predator is very nice! The colour suggests exactly exactly the same pigment relationship as Okenia rosacea has with Integripelta bilabiata in California - i.e. the presence of hopkinsiaxanthin in both prey and predator.
Dennis Gordon
d.gordon@niwa.co.nz
Gordon, D., 2005 (Feb 4) Bryozoan food of Okenia cf. hiroi from NZ . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13070Thanks Dennis,
Is very helpful to have an expert on bryozoans to help with identifications. It's not easy to get good identfications for nudibranch food and as can be seen from this animal, identifying the food greatly enhances our knowledge and ability to interpret these observations. Ian Skipworth's Okenia from the Poor Knights Islands in NE New Zealand [message #12958] looks very similar to Okenia hiroi from the NW Pacific and Okenia rosacea from the NE Pacific. Interestingly, these are the only two species of Okenia we know that feed on eurystomellid bryozoans, O. hiroi on a species of Eurystomella, and O. rosacea on Integripelta bilabiata. So Dennis Gordon's identification of the bryozoan as a Eurystomellid confirms the relationship between the Poor Knights Okenia, and the other two. Without a specimen to examine though, it is all very tantalising.
Best wishes,
Bill Rudman
