Re: First record of Okenia zoobotryon from Australia

January 31, 2008
From: Leanne & David Atkinson


Concerning message #12656:

Dear Bill,
Following on from our message [#21335] about Okenia pellucida at Port Stephens here is a note about Okenia zoobotryon we found at the same time in the same bryozoan. The Okenia were difficult to see because they were so tiny. We used the minimum focus 1:1 of our macro lens to even see them. When we put the images on the computer it was easy to see that the host was covered with an "infestation" of Okenia pellucida. We also found in one of the 6 photos of Okenia pellucida two tiny brown spotted nudibranchs that we didn't see when we took the photo. It is not a good angle to see the details of their bodies. What we can see makes us think they are Okenia zoobotryon. We are sending the original photo uncropped and a cropped version which shows the 2 brown spotted nudibranchs. [Upper Photo: Whole photo with large O. pellucida clearly visible. Lower Photo: Closeup of lower right corner of upper photo showing brown spotted O. zoobotryon.] We've looked at the information on Okenia mija as well but these don't have the white spots or the yellowness of the body shown in the Okenia mija photos. We will keep looking to see if we can find some more.

Locality: Halifax Sponge Gardens, Port Stephens - Great Lakes Marine Park, Port Stephens, 15 metres, New South Wales, Australia, Pacific, 30 December 2007, Sandy bottom with scattered sponges, ascidians, soft corals, bryozoans and kelp. Length: 5 mm.  Photographer: Leanne & David Atkinson.

Best wishes,
Leanne & David Atkinson

atk@hunterlink.net.au

Atkinson, L. & D., 2008 (Jan 31) Re: First record of Okenia zoobotryon from Australia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21336

Dear Leanne & David,

Species of Okenia seem to be fairly specific in the species of bryozoan they eat and until now O. mija has only been found on Amathia wilsoni while O. zoobotryon, as its name suggests, feeds on Zoobotryon verticillatum. That is not to say that O. mija may also eat Zoobotryon verticillatum, but at present we have no evidence that it does, so you identification of these animals as O. zoobotryon is most likely correct. I must say I can't really see enough in your photos to determine the shape of the animals but I can see one rhinophore [ringed] and it appears to have the three cup-shaped lamellae which are characteristic of O. zoobotryon. The lamellae in O. mija are more numerous and have a notch in the posterior midline.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Jan 31). Comment on Re: First record of Okenia zoobotryon from Australia by Leanne & David Atkinson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21336

Factsheet

Okenia zoobotryon

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