Potentiation of l-canavanine-induced developmental anomalies in the tobacco hornworm, Manduca sexta, by some amino acids

Abstract

The growth and development of final-stadium tabacco hornworm Manduca sexta (Sphingidae) larvae fed a 2.5 mM l-canavanine-containing diet is disrupted markedly. Such canavanine-mediated disruption of larval growth is intensified greatly when these organisms are fed a canavanine-containing diet supplemented with a 1 : 10 molar ratio of l-arginine, l-citrulline, l-ornithine or l-2,4-diaminobutyric acid, the larvae possess enhanced haemolymph volume (oedema) and a significant mortality results from incomplete larval-pupal ecdysis. Two other compounds, 3-aminobutyric acid and l-2,3-diaminopropionic acid, do not produce larvae showing oedema but most larvae fail to complete larval-pupal ecdysis. 4-Aminobutyric acid, l-threonine and l-glutamic acid are much less potent but they still manifest appreciable developmental aberrations. Eighteen other tested compounds have no discernible effect. In general, compounds accentuating the biological activity of canavanine have: an α-carboxyl and α-amino group; a carbon skeleton of no less than 2 nor more than 4 carbon atoms; and and ω-amino group.