The Pigmentation of Cavernicolous Animals

1. The widespread reduction of pigmentation found in cavernicolous animals is discussed. 2. The externally visible coloration of Asellus aquaticus Linn., A. meridianus Rac., and A. aquaticus cavernicolus Rac., appears to be of the melanin type. 3. The melanin content of A. aquaticus is not appreciably affected if this animal is kept in the dark for periods of several months. Offspring produced during this period are normal in colour. 4. Fertile young resulted from a cross between a colourless female A. aquaticus cavernicolus and a normally pigmented male A. aquaticus. This observation is probably of significance for the genetical analysis of the colour types found among the hypogean asellids. 5. The predominant pigments of A. aquaticus, apart from melanin, are β-carotene and cryptoxanthine. Other carotenoid pigments are present only in traces.