Spurilla macleayi - colour variation

February 9, 2004
From: Bill Rudman

Here are photos of three more animals to accompany my other messages illustrating colour variation in Spurilla macleayi [see messages #12134, #12135].

A. Goat Island Beach, Ulverstone, Nthn Tasmania 20 Feb 1984, intertidal;
12mm long alive, AM C141279. Photo: Bill Rudman. - The main colour in this specimen is the opaque cream white, which forms a patch on the head, another behind the rhinophores, a ring around the pale ornage pericardium, and then smaller patches between each group of cerata down the dorsal midline. In this animal, the usually characteristic subterminal yellow ring on the cerata is reduced to a broken series of dashes.

B. 7 Kms south of Mallacoota, Victoria, Australia. 28 February 1982. 12mm long. AM C138022. Photo: Bill Rudman. - In this animal the boody wall is translucent with almost no sign of opque white speckling. There is some orange dusting on the head and there is a very bright orange pericardial patch. On the cerata, the yellow ring is the only epithelial colour.

C. Goat Island Beach, Ulverstone, Nthn Tasmania, Australia. 20 Feb 1984, intertidal; 15mm long alive. AM C141279. Photo: Bill Rudman. - Found with the animal A, the opaque white patching down the dorsal midline is more developed than in the other animal.

It has been suggested that the colour variation in this species may indicate a complex of species. However it is equally likely that with a direct developing larval stage, local colour forms are likely to occur through restricted gene flow. All animals show parts of the colour pattern. nearly all have the yellow subterminal ceratal ring, and most have some indocation of an orange patch over the pericadium. The other major feature of the colour pattern - a white patch on the head, another behind the rhinophores, and a series of white patches in the dorsal midline in the interceratal spaces - is less common, but traces of the pattern are often present.

Best wishes
Bill Rudman

Rudman, W.B., 2004 (Feb 9) Spurilla macleayi - colour variation. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/12137

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