EFFECTS OF A FERTILITY-REDUCING BACULOVIRUS ON SPERM NUMBERS AND SIZES IN THE INDIAN-MEAL MOTH, PLODIA-INTERPUNCTELLA

1. A dose-dependent decrease in male fertility occurs in the Indian Me al Moth, Plodia interpunctella, when sub-lethally infected with granul ovirus during the larval stage, 2. Here, the causes for this decline: are investigated by examining eupyrene and apyrene sperm numbers and s izes produced by males across four levels of viral challenge. 3. The r esults. could not explain how reduced male fertility is caused in this host-pathogen interaction. While a reduction in both eupyrene and apy rene sperm numbers from all virus-treated males was found, this was no t significant and neither was there a difference in sperm lengths acro ss the four treatments, There were also no differences in the variance s of sperm numbers or lengths between the doses, and no associations b etween sperm numbers or lengths and body size were found. 4. A signifi cant correlation between eupyrene and apyrene numbers was found, but t his was independent of dose, Significant between-male variance in apyr ene sperm lengths was found, indicating that individual males differ i n the range of apyrene sperm sizes they produce. 5. It is suggested th at further intracellular and behavioural study is needed to identify t he causes of the granulovirus-induced reduction in fertility of P. int erpunctella.