Pink bollworm : effects of male irradiation and ejaculate sequence on female ovipositional response and sperm radiosensitivity

Males of Pectinophora gossypiella (Saunders) were treated with 20 krad of gamma irradiation at 2 or 3 days postemergence and then placed with 1 virgin female every 24 h for 4 consecutive transfers. Mating, amount and kind of sperm received, egg production, and egg hatch were recorded for each female. In this manner, we could determine whether a male mated with all 4 or fewer than 4 females and whether the 1st ejaculate occurred with the 1st or a subsequent female and could compare the results with oviposition and hatch records. There was no significant difference in the frequency of mating between irradiated and control males: 85% of control males mated an avg of 2.4 times; 83% of treated males mated an avg of 2.2 times. The 1st and 2nd matings were similarly distributed in both groups of males. However, there was a highly significant difference in the 3rd mating; 63% of the control males mated for the 3rd time with the 3rd female, compared to 33% for the irradiated males. Both irradiated and control males transferred similar amounts of eupyrene sperm in the 1st ejaculate. The amount of sperm received was significantly lower in subsequent ejaculates, and was significantly lower in females that mated with irradiated males than in those that mated with control males. The 1st ejaculate by either control or irradiated males elicited a greater ovipositional response than subsequent ejaculates, but irradiated males did not elicit as great an ovipositional response as control males. There was no significant difference whether the 1st ejaculate occurred with the 1st female or with females 2-4. We found a significant reduction in hatch of eggs fertilized by irradiated sperm, but there was no significant difference in egg hatch in females that received any of the ejaculates from an individual male.