Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/1996
Publication Date: N/A
Interpretive Summary: Our present understanding of the regulation exerted by parasitic wasps on proteins found in the hemolymph (blood) of their host insects has been limited to the accurate and detailed recording of the protein concentrations. By comparing the response of one host insect, parasitized at different growth stages, by two closely related wasp species, details of fthe wasp-host interaction have been obtained that further explain the function of the host protein alterations. Young host larvae do not contain sufficient nutrient to sustain the development of the wasp and therefore the wasp may increase the concentration of host proteins to extend the period of time that the young host will remain viable. In contrast the older host larvae do contain adequate nutrient for the wasp development, and in that case the reduced concentration of hemolymph proteins in parasitized hosts may suppress host growth to allow for complete wasp development. These results support the concept that parasitic wasps regulate the biochemical composition of the host to provide adequate nutrition for their own development.
Technical Abstract: Two major similarities were observed in larvae of Heliothis virescens parasitized by either Euplectrus comstockii or Euplectrus plathypenae. Parasitism by either parasitoid arrested larval-larval ecdysis and caused comparable alterations in the titer of storage proteins found in the host hemolymph. Parasitized 3rd instar larvae increased in weight to ca. twice that of control larvae while parasitized 4th and 5th instar larvae increased in weight to the maximum observed in control larvae for that stadium. The titer of storage proteins present in the hemolymph increased in parasitized 3rd and 4th instar larvae but decreased in parasitized 5th instar larvae, by comparison to the titers found in control 3rd, 4th and 5th instar larvae, respectively. Consequently, parasitized 3rd instar larvae responded differently by exceeding the normal larval weight and parasitized 5th instar larvae responded differently by demonstrating a decline in the titer of storage proteins in the hemolymph. Feeding by the parasitoids did not cause further alteration in the composition of the hemolymph proteins of the host. A plausible explanation for the increase in weight and/or increase in the storage protein titer in the younger host larvae is to provide a sufficient nutritional source to extend the viability of the host while it remains in that stadium and is fed upon by the developing parasitoids.