Egg-laying Okenia rhinorma

January 18, 2010
From: John Chuk


Dear Bill.

Here is an in situ shot of an Okenia rhinorma specimen found laying an egg ribbon at night. The specimen is partially buried in a silty sand bottom and was found in the same vicinity as the specimen seen in my previous message [#23109]. The egg ribbon is a loose spring-like spiral of flat ribbon containing small white eggs. When complete the egg ribbon is attached to the sediment by a gelatinous anchor.

The second shot shows a typical egg ribbon photographed on a later dive. This was one of eight egg ribbons in a square metre. I have found other groups of similar egg ribbons nearby leading me to assume there is a healthy population of the species at the site at present.

Locality: Blairgowrie, 8m, Victoria, Australia, Port Phillip Bay, 28 December 2009, silty sand. Length: 17mm. Photographer: John Chuk.

Best wishes,

John.

jchuk@optusnet.com.au

Chuk, J., 2010 (Jan 18) Egg-laying Okenia rhinorma. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/23110

Dear John,

This type of egg ribbon certainly looks adapted for sand-dwelling, with a single attachment point in the sand. Very interesting. Okenia ascidicola has a very similar egg ribbon [#11689] .

Best wishes,
Bill Rudman

Rudman, W.B., 2010 (Jan 18). Comment on Egg-laying Okenia rhinorma by John Chuk. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/23110

Factsheet

Okenia rhinorma

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