Responses of Megalodiscus temperatus miracidia to amino and sialic acids found in snail-conditioned water.

Analysis of snail-conditioned water (SCW) from Helisoma trivolvis revealed 17 free amino acids. Those in great concentration were glycine, serine, and alanine. The concentration of sialic acid was found to be twice that of the most abundant amino acid. The behavior of miracidia of Megalodiscus temperatus, measured by the contact with return method, to agar cylinders containing single amino acids and sialic acid indicated greater responses to polar molecules charged either positively or negatively at neutral pH. The molecules elicting the greatest response were aspartic, glutamic, and sialic acid. No correlation was found between concentration of amino acids in H. trivolvis SCW and response of M. temperatus miracidia.