|Coudron, Thomas - Tom|
Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/24/1998
Publication Date: N/A
Citation: Interpretive Summary: Studies on natural substances that regulate insect development continue in order to find alternatives to the use of synthetic compounds as insecticides. Parasitic wasps alter the development of their insect host in order to improve the host as a nutritional source and a dwelling location for themselves. Frequently, wasps use a venom to cause these alterations. The present study was conducted to see if the alterations that occur within a natural host of the wasp Euplectrus comstockii, would also occur within an unnatural host, i.e. an insect that would not normally serve as a host for the wasp. This information is valuable to know in order to understand how the venom of wasps may be used to control several insects that are pests of agricultural crops. The results indicated that the venom is able to stop growth in both natural and unnatural insect hosts. Therefore, the venom is a valuable bioactive substance for researchers, and studies of the active substances within the venom may result in the use of natural substances to control a wide range of insect pests. It is interesting to note that the venom did not cause all of the biochemical changes in unnatural hosts that have been observed in natural hosts. The differences in biochemical responses is important information and will be used to assist in our desire to understand the mechanism by which the venom causes the effects that it has on the insect hosts and will be used by other researchers and industry in their efforts to develop effective, environmentally acceptable natural bioregulators to substitute for the synthetic chemical insecticides in use today.
Technical Abstract: Parasitism by Euplectrus comstockii arrested larval-larval apolysis and ecdysis in both permissive (e.g. Helicoverpa zea) and non-permissive hosts (e.g. Diatraea grandiosella, Anagasta kuehniella, and Ostrinia nubilalis). Parasitized larvae of both permissive and non-permissive hosts manifested a decrease in total weight gain. However, significant alterations of the hemolymph proteins occurred only in the permissive host. Therefore, the venom of Euplectrus causes some, but not all, of the same effects in non- permissive hosts as in permissive hosts. Specifically, the ability of the venom to regulate ecdysis was shown to be distinguishable from the ability of the venom to alter the protein titer in the hemolymph of a host. The fact that parasitoid eggs did not hatch on non-permissive hosts indicated that parasitoid development was impacted prior to feeding on the host, and supports the concept that the increase in the hemolymph protein titer in permissive hosts may serve 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.