Mating Thuridilla gracilis from nthn Mariana Islands
January 30, 2007
From: Yuji Fujie
Dear Dr.Bill,
Here we have three pictures from maybe mating Thuridilla gracilis. They were spinning in the same place. This animal is very common in Saipan but I haven't seen them doing this behaviour before.
Locality: LauLau Beach, 6m, Saipan, Northern Mariana Islands, Pacific Ocean, 21 January 2007, on the dead coral. Length: 20mm. Photographer: Yuji Fujie.
Would you tell us what is the part inside circle, please ?
Best regards,
Yuji
dswith@isletwind.com
Yuji Fujie, 2007 (Jan 30) Mating Thuridilla gracilis from nthn Mariana Islands. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19315Dear Yuji,
Firstly this colour form is what some people would call Thuridilla bayeri [see message #3077]. I am pretty sure that the whitish lump on the right side, at the base of the rhinophore, which you have ringed, is the penis. Two elysiids twisted around each other like this - as you say 'spinning' - is almost ceratinly a mating or copulatory behaviour. In the photo alongside, both animals are wrapped around each other with their penises everted. I am not sure in the photo if the animals are trying to insert their penises into their partner's genital opening or whether they are trying to inject the sperm into the partner's body cavity. Quite a few sacoglossans practice hypodermis insemination in which sperm is transferred, not via the vagina but directly throught the body wall. Hopefully Kathe Jensen will be able to give us her opinion
Best wishes,
Bill Rudman
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