| Popis: |
A white mutant of the tobacco hornworm, Manduca sexta , was discovered among wild-type, blue-green larvae in a laboratory colony routinely supplemented with field-collected insects. The mutant is pinkish-white when reared on artificial diet and maintains this coloration from egg hatch through pupation. Spectral analyses showed that the blue chromophore, biliverdin, which is present in the integument and plasma of wild-type, diet and tobacco-reared larvae, was lacking in the white mutant reared on the same diets. Insecticyanin levels determined by radial immunodiffusion in the integument and plasma of the white mutant were half that of normal blue-green larvae. The topical application of increasing amounts of the juvenoid, 2-(1-methyl-2-(4-phenoxyphenoxy)ethoxy)pyridine, to wild-type, day 1 first stadium larvae of M. sexta was positively correlated with the intensity of white coloration, which first appeared in newly molted second instars and was retained until pupation. White-mutant larvae developed slower and were slightly larger than wild-type larvae. The corpora allata from last stadium, day 0 larvae of the white mutant demonstrated a higher rate of JH/JH acid biosynthesis and the hemolymph had a higher titer of JH than the wild type of the same age. These studies suggested that JH may play a role in the regulation of the white phenotype. No differences were noted in the level of JH esterase activity between the two strains during the last stadium. |
