The Role of Algae in the Diet of Asellus aquaticus L. and Gammarus pulex L.

Abstract

The food of Asellus aquaticus L: and Gammarus pulex L. consists of decaying vegetation, microscopic algae and invertebrate animals. Several workers have examined the gut contents of these and related species, and have concluded that allochthonous leaf material is the most important food in the diet (Haempel 1908; Willer 1922; Steusloff 1943; Levanidov 1949; Hynes 1954, 1963; Minckley 1963; Minshall 1967). Other workers have reared Asellus or Gammarus on a diet of decaying leaves and have concluded that the animals were feeding to a large extent on the epiphytic fungi and bacteria on the leaves (Hynes & Williams 1965; Kaushik & Hynes 1971; Prus 1971, 1972; Barlocher & Kendrick 1973a, b; Nilsson 1974). The other components of the diet have usually been ignored by most workers, but Margalef (1948) reported that G. pulex fed chiefly on insects and copepods, and Deksbakh & Sokolova (1965) stated that G. lacustris Sars fed chiefly on algae, macrophytes and invertebrate animals. Hynes (1970) notes that most of the information on invertebrate feeding is qualitative and thus serious errors may exist in the estimation of the relative importance of the different dietary components. As the algal component of the diet has been neglected by most workers and is relatively easy to quantify, a detailed study was made of their role in the diet of Asellus aquaticus and Gammarus pulex. Samples were collected from rocks and growths of Cladophora glomerata (L.) Kz. in three rivers of south-western England between June 1973 and May 1974.