TYROSINE AND CATECHOLAMINE LEVELS IN THE HEMOLYMPH OF TOBACCO HORNWORM LARVAE, MANDUCA-SEXTA, PARASITIZED BY THE BRACONID WASP, COTESIA-CONGREGATA, AND IN THE DEVELOPING PARASITOIDS

Parasitism of fifth instar Manduca sexta larvae by the gregarious para sitoid Cotesia congregata prevented normal storage of tyrosine in the hemolymph, whereas total tyrosine levels increased over eight times in the hemolymph of unparasitized larvae by day 4. Tyrosine glucoside, t he hemolymph storage form of tyrosine and the precursor for pupal cuti cle sclerotizing agents, was found only in trace amounts in parasitize d larvae at the time of parasitoid emergence, but had increased to ove r 6 mM in hemolymph of unparasitized larvae. Concentrations of dopamin e and N-beta-alanyldopamine (NBAD), precursors for melanization and sc lerotization of cuticle, respectively, had approximately doubled in th e hemolymph of parasitized larvae by the day of parasitoid emergence, but not in unparasitized larvae. Catecholamine biosynthesis may be tra nsiently stimulated for wound-healing, as black melanic pigmentation a ppeared around the wasp emergence holes in the host integument. C. con gregata larvae accumulate tyrosine, dopamine, and NBAD by the time of emergence and cocoon spinning, either by direct uptake or by synthesis from precursors obtained from the host. NBAD increased in parasitoid larvae close to pupation, suggesting it functions as the main precurso r for pupal cuticle tanning. Both dopamine and NBAD increased dramatic ally in pharate adult wasps just before eclosion and N-acetyldopamine (NADA) appeared for the first time. Dopamine was highest in concentrat ion and total amount, and it can serve both as a precursor for black m elanic pigmentation of adult wasp cuticle and for synthesis of NADA an d NBAD, the precursors for cuticle sclerotization. Arch. Insect Bioche m. Physiol. 38:193-201, 1998. (C) 1998 Wiley-Liss, Inc.