Single Copulation Research Articles

Mating Behavior, Egg Production, and Egg Fertility In the Pear Psylla1

Through observation of the mating behavior of individual pairs of pear psylla, Psylla pyricola Foerster, caged on Bartlett pear seedlings in a greenhouse, the following characteristics of their reproduction were determined. females produced fertile eggs only after mating, although unmated females deposited a few infertile eggs. Males had a precopulatory period of about 5 days after their final molt, while females could mate successfully within a few hours after molting. One male had a mating capacity to fertilize 4 but not 6 females to full oviposition, while a ratio of 4 or more males per female reduced oviposition rates. Neither extreme affected egg fertility. Males were the aggressors in the mating act and had a capacity of mating about once a day through the first 2 weeks as adults. Females remained fairly passive and did not refuse the advances of the males. The duration of single copulations varied from less than 1 minute to 3 or 4 hours, and averaged 36 minutes. Mating took place at all hours but most frequently in the early afternoon when it was warmest and brightest. To produce fertile eggs at full capacity a female had to mate at least once every 10 days. Mating with the same male, compared with mating with a different male each time, resulted in no significant difference in frequency or duration of mating and no difference in oviposition rate of females or egg-fertility. When females were allowed to mate freely, oviposition reached a peak of 12-14 eggs per day by the third week. A decline in oviposition rate began after about 39 days, nearing 0 in 12 weeks, when most psylla were dead. Total eggs laid averaged 664 per female. Fertility level stayed near 100%, dropping slowly the last 2 to 3 weeks to about 75%. When females were restricted to one mating the oviposition rate declined soon after the 19th-day peak, nearing 0 within 11 weeks, when most psylla were dead. Total eggs averaged 315. Fertility level dropped steadily after the third week from near 100% to 0 by 7 weeks. When mating was interrupted after 2 weeks, fertility dropped steadily to 0. returning quickly to near 100% following reintroduction of males 32 days later. Oviposition rate also decreased during the absence of males, increasing again upon reintroduction. Females with mating interrupted continued to lay eggs longer than those with uninterrupted mating, averaging 608 eggs each during 14 weeks. In most cases females died before the males. Females from the single mating group generally died sooner than females from the other groups. In all groups the sex ratio of the progeny was nearly 1:1. Males matured faster than females; thus. from eggs deposited at any given time there were at first more males followed by a preponderance of females among the emerging adults.

Tests for Chemical Mutagens in Drosophila Using the Vaginal Douche Technic.

SummaryVaginal douches of 4% methyl bis (β-chloroechyl) amine hydrochloride produced 53 lethals in 5488 egg and sperm X chromosomes tested while only 13 lethals were observed in the 6271 sperm or egg X chromosomes tested after treatments with formaldehyde, copper sulfate, 2,4-dinitrophenol, hydrazine hydrate and trypsin. The practicality of the vaginal douche technic for the induction of mutations with N mustard in both sperm and eggs, suggested from previous experiments, is confirmed in that 30 lethals occurred in the 2951 sperm tested and 23 in the 2537 eggs tested. The number of sperm X chromosome lethals seems to be considerably higher in F1 females resulting from single copulations within a two hour period from the time of injection (23 lethals in 1416 tests) than it is in females from copulations after this interval (7 lethals in 1535 tests); the mutation rate for the egg X chromosome under these conditions remains apparently unaffected (9/1083 and 14/1454, respectively). Whereas the 30 sperm lethal...

Utilization of Sperm by the Female Drosophila Melanogaster

The number of sperms transferred by a 4- to 5-day-old wild-type male of D. melanogaster in a single copulation has been found by actual count to approach 4,000. In successive copulations the number rapidly decreases, until after a few matings no sperm is transferred. By the next day, however, additional sperm may be available for transfer. The amount of sperm transferred in a single copulation is only sufficient to guarantee ferilization of all eggs laid during the first few days by the average female. On subsequent days the percentage of sterile eggs increases, so that toward the end of the egg-laying period practically all eggs deposited are unfertilized. A measure was made of the ability of sperms of three types of males, namely, wild-type, Curly/Glazed and plexus brown speck, when used in all possible mating sequences, to take precedence in fertilizing the eggs of plexus brown speck females. The Curly and Glazed off-spring from these crosses were slightly more frequent than the wild-type; the plexus brown speck represented only about one sixth of the total progeny. Similar proportions were found among the offspring of plexus brown speck females, which were permitted to lay their eggs in the same bottle, after each had mated with only one of the types of males available. Such similarity suggests that the differences in frequency of different classes of offspring following polyandry are referable to differential viability of the different types of embryos and larvae, and not to differences in vigor or mortality of the various types of sperms leading to selective fertilization.