Carotenoids Found in Littorina Littorea (L.) and Their Relationship to Parasitic Infection by Larval Trematodes

Abstract

Littorina littorea from Long Island Sound feeds primarily on the algae: Chlorophyceae (three species) and Rhodophyceae (two species). Carotenoids from the algae are accumulated in different tissues of the snail in either an unchanged state or metabolized. 3-carotene, the major pigment in green and red algae, was isolated from the foot, hepatopancreas and nephridium of these snails. Six oxygenated carotenoids, not completely identified, were isolated from the same tissues. The snails show a variation in foot color from white to brown to red. Littorina littorea is parasitized by the trematode larvae of Cryptocotyle lingua and Cercaria parvicaudata from which 3-carotene and one oxygenated carotenoid were isolated. Contrary to previous work, there is no relation between foot color of the snail and parasitic infection. Neither age nor sex appeals to have any relation to foot color. Although carotenoid pigments are known to cause the variation in foot color, the reasons or factors for their accumulation in the snail tissue have not been established. Some hypothetical explanations are discussed.