Submitted to: Pan American Symposium on Animal Plant and Microbial Toxins
Publication Type: Abstract Only
Publication Acceptance Date: August 2, 1995
Publication Date: N/A
Technical Abstract: Parasitism by hymenopteran species is a complex phenomenon; affecting the behavior, physiology and development of its host insect. The adult female parasitoid has the capability of regulating the host for the advantage of her offspring in order to provide a suitable source of nutrition and dwelling. Ectoparasitoids often rely on a venomous material produced by specialized tissues to regulate their hosts. Venomous substances of ectoparasitoids often affect the central nervous system or the endocrine system of the host. One of the better studiednon-paralyzing venoms from an ectoparasitoid is produced by Euplectrus species in the family Eulophidae. The physiological effect of their venom is unique and causes an arrestment of the larval-larval molting process in the host. The substance arrests apolysis and ecdysis of the larval cuticle of the host. The occurrence of molt arrest in isolated tissues indicates that the venom may have a direct action on epidermal tissues, by gene regulation, thereby causing a cessation of cell division and an arrestment of ecdysis. The venom also causes processing of the host ecdysteroid milieu. However, arrestment is not reversible with treatments of juvenile hormone, methoprene, or 20-hydro permanent antiecdysteroid effect on the host. To date, only Eulophidae species and baculoviruses are known to arrest larval ecdysis in their hosts without causing paralysis. The pathogenic baculoviruses accomplish this by encoding for the enzyme ecdysteroid UDP-glycosyltransferase (EGT). Our studies showed that EGT activity was absent in the eulophid venom, which suggests that parasitic eulophids have developed a different and unique regulatory mechanism.