1990 Fiscal Year Final Research Report Summary
Mating Systems and Sperm Competition in Insects
| Project/Area Number |
63540518
|
|---|
| Research Category |
Grant-in-Aid for General Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
生態学
|
|---|
| Research Institution | National Institute for Environmental Studies (1990)
Nagoya University (1988-1989) |
|---|
Principal Investigator |
TSUBAKI Yoshitaka National Institute for Environment Groval Environment Research Group, Head of Laboratory, 地球環境研究グループ, 総合研究官 (30108641)
|
|---|
| Project Period (FY) |
1988 – 1990
|
| Keywords | Sperm competition / Damselfly / Army worm / Spermatophore / Phase variation / Remating / Melon fly / Sperm longevity |
|---|
| Research Abstract |
Mechanisms of sperm competition in three taxonomical groups of insects was studied in order to understand their mating systems.
1. Males of the damselfly Mnais pruinosa pruinosa were observed to use three different tactics to secure mates. The mean duration of copulation differed between the three observed tactics and resulted in varying degrees of sperm removal and insemination. A variety of factors which might influence copulation duration were invesitgated. The most important was the location of the site at which males captured thier mates.
2. Males of the melon fly Dacus cucurbitae copulate for 10 hours or more, usually starting at dawn and terminating at dusk. The amount of sperm transferred to a female increased with time after mounting. Mating duration was a major determinant of paternity when females were doubly mated. However, "last male's advantage" in sperm precedence was observed when the mating interval was longer than 10 days. Counting the number of sperm in spermatheca under a microscope, mean longevity of sperm was estimated as 17 days. As a proportion of the first male's sperm die before a second mating has occurred, sperm precedence value would increase without any sperm displacement mechanism.
3. Variation in spermatophore size was studied in relation to larval rearing density in the armyworm, Leucania separata. Males grew under a high density condition produced larger spermatophore than solitary males, in spite that the body size was not different between them. Spermatophore size increased with male age or time interval between previous and current matings. Females that received large spermatophore delayed remating longer than those receiving small ones.
|
