EFFECTS OF HIGH-TEMPERATURE SHOCKS ON MALE GERMINAL CELLS OF TRICHOGRAMMA-BRASSICAE (HYMENOPTERA, TRICHOGRAMMATIDAE)

In the field, drops in the parasitic efficiency of the oophagous paras itoid Trichogramma brassicae have been observed in certain climatic co nditions (high temperatures). These effects were due in particular to a decrease in the proportion of females in the parasitoids' offspring. Several hypotheses could explain these results. We supposed that male s were thermosterilized. This study corroborates this hypothesis. Tric hogramma brassicae has 2 type of spermatozoa: typical spermatozoa and atypical ones. At emergence, all the spermatozoa have reached the semi nal vesciles and the testes are empty. After the white pupae age, ther e are no more apical spermatogonia to assure germinal cell renewal. Th e thermal treatment effect depends on temperature, treated age, and tr eatment duration. In the experimental conditions reported here, primar y spermatocytes were the most susceptible stage. A heat shock of 44-de grees-C for 6 hours at this stage induces pycnosis of nearly all the g erminal cells, leading to an offspring without daughters.