Four effects of elevated temperature on chiasma formation in the locust schistocerca gregaria

Abstract

Using an inbred stock of Schistocerca gregaria in which inter-individual variation was reduced, the effects of high temperature treatments on male meiosis have been investigated. These experiments involved both heat-treatments of relatively short duration, ranging from 1-6 days at 40°C followed by a return to 30°C, and longer periods of time at a constant 40°C. It was found that four effects on chiasma frequency could be produced. In addition to the major reduction in chiasma frequency reported earlier, a second small period of reduction was obtained. The other two effects involved increases in chiasma frequency. Three of these effects, the two decreases and one increase, were produced following heat-treatments of meiotic prophase stages, after premeiotic DNA synthesis was completed. The other increase was obtained following heat-treatment of spermatogonia. The possible nature of these effects is discussed. It is suggested that the late prophase period, during which a small increase in chiasma frequency (called EfTect 1) is produced by heat-treatments, could correspond to at least part of the time during which chiasmata form. © 1988, The Genetical Society of Great Britain.