Arylphorin of Trichoplusia ni: Characterization and parasite‐induced precocious increase in titer

Abstract

AbstractArlyphorin (Ap) is the principal protein of the last larval instar hemolymph of Trichoplusia ni. It was shown to be homologous with the Aps of Manduca sexta and Lymantria dispar by Western blot and quantitative immunoelectrophoresis. Another hemolymph storage protein in T. ni of lesser titer was shown to be homologous with larval hemolymph protein (LSP) of M. sexta. Ap titer increased dramatically in the last larval instar of T. ni, as in other holometabolous insects studied. Parasitization by Chelonus sp. caused the Ap titer to rise prematurely in the penultimate larval instar of T. ni. This rise in Ap in the fourth instar is one of the earliest diagnostic signs of parasitization. Among the suite of behaviors of the Chelonus larva on exiting the host is depletion of the host cadaver of most remaining protein. The T. ni Ap titer in the alimentary tract of Chelonus peaks at that time and declines to zero in the first 24 h after parasitoid emergence, prior to its pupation. Aps are a source of phenolic storage compounds. Hence, premature induction of T. ni is advantageous for the parasitoid's own pupation and adult development.