February 11, 2006
From: Takao Urasawa
Dear Dr Rudman
Thank you for you welcome advice every time.
This Siphopteron is very small. It's body is lemon yellow and red. -A beautiful colour pattern.
Locality: Laulau Beach, 6m, Saipan Northarn Mariana Islands, Pacific Ocean, 05 February 2006. Length: 1.5 mm. Photographer: Takao Urasawa
email@example.comTakao Urasawa, 2006 (Feb 11) A juvenile Siphopteron nigromarginatum. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15773
I thought at first this was Siphopteron flavum but I am pretty sure it is a juvenile Siphopteron nigromarginatum which has not yet developed all its colours. Have a look at Yasuhiro Shirai's photos  which show a similar colour pattern - where your animal is translucent clear, his animal has a bluish pigment. The two red-brown spots on the edge of the parapodia are I guess the beginnings of the black line along the edge of the parapodia which give this species its name.
In many opisthobranchs black pigments start as a reddish brown colour in the juveniles. Even in adults the normal black color can be replaced by orange as occurs in Chromdoris hamiltoni and other chromodorids with black lines. I am sure a chemist could explain what is happening here, but it seems that when te black pigment is not present in sufficient quantity we get these red-browns or oranges.
Siphopteron nigromarginatum from Hachijo
From: Nishina Masayoshi, August 12, 2002
Siphopteron nigromarginatum? from Kii Peninsula
From: Yasuhiro Shirai, August 23, 2001
Re: Siphopteron cf. brunneomarginatum
From: Nishina M. & J. Imamoto, August 4, 2001
Re: Siphopteron from Japan
From: Terry Gosliner, August 2, 2001
Siphopteron cf. nigromarginatum from Japan
From: Nishina Masayoshi, August 1, 2001