Extracellular electrical activity from the photoreceptors of midge.

The ontogeny of photosensitivity has been studied in a holometabolous insect, the midge Chironomus ramosus. The life cycle of midges shifts from an aquatic environment to a non-aquatic environment. Extracellular electrical activity of photoreceptor organs was recorded at larval and adult stages. We found an increase in photosensitivity as the larva metamorphosed to the adult stage. This is the first report of changes in photosensitivity during the development of any insect described in an ecological context.

Heat shock response in ovarian nurse cells of Anopheles stephensi.

Transcriptional and translational changes following temperature shock at 37, 39 or 41°C to ovarian cells of Anopheles stephensi were studied. Temperature shock at 39°C induced 6 puffs on polytene chromosomes in the nurse cells as revealed by [3H] uridine incorporation studies. Only the 2R-19B puff was induced at 37°C and was found to be a major temperature shock locus remaining most active at all the 3 temperatures tested. Other temperature shock loci were activated only at 39°C. There was progressive inhibi tion of general chromosomal transcription with the rise of temperature. Transcription was drastically inhibited at 41°C but all the temperature shock loci still remained relatively active. Examination of [35S]methionine labelled newly synthesized ovarian proteins using sodium dodecyl sulphate-polyacrylamide slab gels revealed that all the heat shock polypeptides except the HSP 70 were synthesized in ovarian cells even at control temperature (29°C). Temperature shock induced the synthesis of HSP 70 and elevated the levels of other heat shock polypeptides (82, 30, 29, 23 and 17 KD). Present results suggest that the threshold level for induction of a complete heat shock response in mosquitos is higher (39°C) than the other dipteran insects studied and that a 41°C treatment is not lethal as in the case of Drosophila, Chironomus etc. These features reflect the adaptations of mosquitos to tropical climate and their dietary habit of warm blood meal.