Colour variation in southern Tasmania populations of Heliocidaris erythrogramma (Echinometridae: Echinoidea)

Abstract

Four populations of Heliocidaris erythrogramma in southern Tasmania showed considerable colour variation of the calcareous spines and test (white, violet, green or violet and green) as well as of the dermis (white, dark red or occasionally pink). The three major pigments of the calcareous parts were identified as Spinochromes A, B and C. The dermis contained pigment granules that consisted mainly of echinochrome A together with an unidentified iron-containing pigment. The variation in dermal pigmentation had a major effect on the appearance of the live urchins and is unusual among echinoids. The proportions of colour morphs varied both within and between populations, strongly suggesting that colour variation is controlled by environmental and/or genetic factors. A correlation between exposure of a site to wave action and dermal pigmentation was observed; urchins with a white dermis were found in much higher proportions at the most exposed site. Other possible ecological and evolutionary explanations for the variation are discussed.