GROWTH OF THE SALT-MARSH PERIWINKLE LITTORARIA-IRRORATA ON FUNGAL AND CORDGRASS DIETS

The growth of the salt marsh periwinkle Littoraria irrorata (collected from Sapelo Island, Georgia in 1991, initial shell length 6.2 to 11.5 mm) on various diets was measured. Growth was highest on a diet of standing-dead leaves of Spartina alterniflora. Periwinkles provided with marsh sediment, yellow-green, sterile, or bacteria-colonized leaves lost organic mass. Fungal-colonized leaves and pure mycelia of fungi common on standing-dead leaves allowed intermediate growth. Growth on S. alterniflora-based diets was negatively correlated with the phenolics content of the food, and positively correlated with its lipid content. No correlation was found between growth and protein content. The digestibility of S. alterniflora leaves, estimated with the acid-insoluble ash technique, was highest when yellow-green leaves were used. Colonization by fungi or bacteria caused it to decline. For S. alterniflora-based diets, growth rates were positively correlated with the amount of time spent on the food.