Sea Hare eggs
September 21, 2000
From: Nerissa Bontia
Dear Bill,
I am researching on the different web sites and I was so happy when I came across into the Sea Slug Forum. I have read the different messages about sea hares but i've got only a little information regarding the sea hare's egg mass. I am a State College Professor, interested to study on the egg mass of the sea hares specifically Dolabella auricularia which is very common in our country [The Philippines].
Many people are eating these eggs rather than the sea hares itself. What nutrients could we get from the egg? If sea hares are toxic what particular part of the body is affected? Is there a possibility that the egg mass will also contain toxin?
I would appreciate much if you could give me some information on this regard.
Very truly yours,
Nerissa Bontia
poner@irepublic.com.ph
Bontia, N., 2000 (Sep 21) Sea Hare eggs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/3047Dear Nerissa,
I am afraid all I know about Dolabella eggs and the possible toxicity of the whole animal is what you will find by reading the other messages on this page. You will find them if you look below your message. I am not sure how familiar you are with web pages but if you click on any underlined topic you will go to a relevant page with more information. In fact the most relevant research has been done in the Philippines.
I can add a little more general information on Sea Hare egg masses.
There are not many records of predators eating the eggs. As far as I can find, only some starfish and the nudibranch Favorinus japonicus. It has been suggested that the reason animals avoid the eggs as food is because they contain distasteful chemicals, in particular secondary metabolites that they obtain from their algal food. However there have been few staudies on the topic. Pennings (1994) offered pieces of egg mass of Aplysia juliana and Dolabella auricularia to crabs and fish but they were rejected. Organic extracts from the eggs of Stylocheilus striatus [as Stylocheilus longicauda] deterred feeding in reef fish at normal concentrations, but the eggs surprisingly did not contain the expected secondary metaobolites.
In another study, Pennings & Paul (1993) could find no secondary metabolites in the egg masses of Stylocheilus, Dolabella or Aplysia californica after adults were fed on either natural diets or diets containing secondary metabolites.
What then makes the eggs distasteful? It has been suggested that it is perhaps related to algal pigments. The egg colour of Sea Hares depends on the colour of the algae they are eating. For example when a Sea Hare changes from green to red algae its egg colour will chnage (Carefoot 1967). The seaweed pigment is transferrd to eggs within 48hrs (Chapman & Fox, 1969,) It is still not clear whether algal pigments are making the eggs distasteful or whether the Sea Hares are producing a new chemical.
Kirstern Benkendorff has just completed a Ph.D thesis [University of Wollongong, NSW, Australia] which included research into the egg masses of Sea Hares. Her findings, when published, will add an interesting new chapter to the story. The papers I have cited can be found on the Sea Hares - Chemical Defence Page.
Best wishes,
Bill Rudman.
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