[Natural amino acids as effective stimuli evoking chemoreceptor-directed behavior in anuran tadpoles]

The behavioral reactions of tadpoles of four anuran species, inhabiting Moscow Region (Rana temporaria L., R. lessonae Cam., Bufo bufo, and Pelobates fuscus Laur.), on solutions of natural L-amino-acids of different concentrations. It was shown that none of the tadpoles respond to solutions of most amino-acids with concentrations less than 10(-2) mole/l. Sequences of relative efficiency of amino-acids as chemical stimuli, inducing feeding behaviour. The sequences display interspecific differences, however, positively correlate in different amino-acid content during pairwise comparison of species. For tadpoles of later developmental stages asparagine, glutamine, and lysine are good feeding behavior stimuli; proline is little or not effective. A reaction of avoidance of arginine, more pronounced in earlier developmental stages was observed in Bufo bufo tadpoles. The sensitivity of different age tadpoles to alanine, valine, glutamine, lysine, ornithine, and proline was studied by registering behavioral responses at different developmental stages. At earlier stages sensitivity is rather high (up to 10(-4) mole/l in R. temporaria tadpoles), and subsequently decreases in ontogenesis to an average level of 10(-4) mole/l. Tadpoles of different species, but similar developmental stages were found to differ in their sensitivity to amino-acids. Experiments with olfactory deprivation of P. fuscus tadpoles showed amino-acid sensitivity to be connected with olfaction, whereas behavioral responses to amino-acid solutions with concentrations 10(-2) mole/l may be connected with any exterochemoreception system.