Re: Siphopteron tigrinum mating

November 15, 2006
From: Yuji Fujie

Dear Dr.Bill,
Following my last message [#18347], I attach 3 photos of Siphopteron tigrinum mating.

Locality: Laulau Beach, 8 m, Saipan, Northern Mariana Islands, Pacific Ocean, 7 April 2006, on the dead coral. Length: 3 mm. Photographer: Yuji Fujie.

Sorry for the poor pictures.
Best regards,

Yuji Fujie, 2006 (Nov 15) Re: Siphopteron tigrinum mating. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Yuji,

Considering the size of the animals I don't think you need to apologise about the quality of the photos - I think its amazing that you got any photos at all.

Like all cephalaspideans, the penis is on the right side of the head and the female genital opening is on the right side near the posterior end of the body. This leads to many cephalaspideans mating in a head to tail position. However this is not always the case and in your upper photo the upper animal (which acting as the male) has approached from the right side, and I am pretty sure I can see the long inflated, almost transparent, penis lying across the open parapodial 'wing' and entering the female genital opening which is under the front part of the visceral hump.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Nov 15). Comment on Re: Siphopteron tigrinum mating by Yuji Fujie. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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