Chelidonura varians - mating behaviour

September 19, 2007
From: Kamal El Tawil

Dear Bill :
On a recent dive trip in Manado, I noticed two Chelidonura varians approaching each other and joining. A moment later a third one joined. Is this common behaviour ? Would you say that is mating ?

Locality: Bunaken marine park, Manado, 5 meters, North Sulawesi , Indonesia, Celebes sea, 13 August 2007, Sandy bottom. Length: 30 mms. Photographer: Kamal El Tawil.

How would you relate the second picture in Danny van Belle's message #19283? I think it involves more than two slugs too.
Kind regards,
Kamal el Tawil
www.coralworld.net

kamal@coralworld.net

El Tawil, K., 2007 (Sep 19) Chelidonura varians - mating behaviour. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20748

Dear Kamal,

Looking through earlier messages on this species, there are a number of observations of three animals 'pairing'. Like all sea slugs, species of Chelidonura are hermaphrodite, with fully functional male and female reproductive systems. In nudibranchs, the male and female organs open together on the right side of the body so for physical reasons only two animals can mate at one time, but when they do so they can act as both male and female at the same time. However in aglajids, like Chelidonura, and in Sea Hares, the male organ - the penis - is situated on the right side of the head, while the female opening is at the posterior end of the body on the right side. This means that when a pair mate, one usually acts as the female, and the other as the male. It also means that if there are more than two animals present they can form a mating chain with the one at the front acting as a female, the one at the back acting solely as a male, but the one[s] in the middle can act as both.

This is discussed more fully on the Mating Chains Fact Sheet. In the messages attached to that Fact Sheet you will see a number on what has been called the Sea Hare Love Drug which is a chemical signal Sea Hares produce when mating. It is possible that aglajids produce a similar chemical signal which would explain why two animals together can quickly attract a third - or more.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Sep 19). Comment on Chelidonura varians - mating behaviour by Kamal El Tawil. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20748

Factsheet

Chelidonura varians

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