Pleurobranchus membranaceus and eggs

May 23, 2002
From: Jim Anderson


Dear Dr. Rudman,
I promised you an image of spawn a year ago, well here at last it is. The animal in the photo was relocated from a couple of metres away to give scale.

Data: 12 May, 2002. South Gortein, Loch Fyne on the west coast of Scotland. One of many 60mm long animals and spawn seen from 7 to 15 metres in 10 degC. The biggest concentration was on the 7 M level at the point where the muddy sand and cobble slope starts. Many spirals of eggs and groups of up to six animals were found in heaps and others mating, egg-laying, eating white ascidians and the odd dead animal among the debris.

This image and others have been added to my Scottish Nudibranchs website.

Kind regards,
Jim A

jander4454@aol.com

Anderson, J., 2002 (May 23) Pleurobranchus membranaceus and eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7001

Dear Jim,
Thanks very much. I am surprised at how large the egg mass is relative to the size of the animal. I found a reference by Tom Thompson (1976) to a study of this species in the Mediterranean by Tchang-Si (1931) who eported that egg ribbons can be very large [1,795,500 eggs per ribbon] and that the egg ribbon takes up water after it is laid so that a 140g adult may produce an egg mass weighing 150g. The eggs are small, and develop into free-swimming planktotrophic larvae. Talking of swimming - I was most impressed with the photo on your website showing an animal swimming just as Thompson & Slinn(1959) described it.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (May 23). Comment on Pleurobranchus membranaceus and eggs by Jim Anderson. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/7001

Factsheet

Pleurobranchus membranaceus

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