Influence of infra-optimal breeding temperature on spermiogenesis of the locust Locusta migratoria: II. Abnormalities in differentiation of the nucleus

Abstract

The sterile males of the Migratory locust that have been raised under infra-optimal temperature conditions produce spermatids with highly abnormal nuclei. These are spherical in young spermatids but later they do not elongate uniformly and they show deep invaginations into which cytoplasmic organelles penetrate. Condensation of the chromatin also is disturbed and the typical honeycomb pattern of the locust spermatid is never achieved. The most advanced stage of condensation that can be reached corresponds to stage 6 of the normal process. Nuclei demonstrating a “stage 6” pattern of chromatin condensation are never thin and slender, as they normally should be at this stage. The shape of the nucleus in these experimental animals seems to be correlated with the pattern of perinuclear microtubules rather than with the state of chromatin condensation. Nuclear abnormalities as well as those regarding the cytoplasmic organelles are compared to several spermiogenetic defects reported in various sterile mutants of Drosophila or in insects submitted to heat-shocks. A total sterility at temperatures only slightly inferior to the usual breeding ones has never yet been reported in insects other than locusts; temperature is thus demonstrated to be a very critical factor for fertility not only when it is too high but also when it does not reach an optimal level.