Free amino acids, ions, and osmotic pressure of the hemolymph of three species of blackflies

Abstract

Hemolymph samples from field-collected larval blackflies Simulium venustum, Simulium vittatum, and Prosimulium mixtum/fuscum were separately analyzed to determine their content of amino acids and several major ions and their osmotic pressures. The hemolymph of the three blackfly species was essentially similar with respect to amino-acid pool, ionic composition, and osmotic pressure. A variety of ninhydrin-positive substances was recorded from the blood of all three blackfly species: the most abundant amino acids were glutamic acid (and its amide glutamine), alanine, proline, glycine, serine, histidine, phenylalanine (and derivative dihydroxyphenylalanine), and lysine. Phosphatide components and several specialized amino compounds normally associated with higher plants and vertebrates were present in the hemolymph. The ionic composition was atypical of Diptera, as potassium and calcium were relatively high. Sodium was found to be the major cation in the hemolymph of all three species. The osmotic pressures of the blackfly blood samples were within the range of values recorded for other aquatic Diptera.