<p>The mechanism of sperm transfer and sperm organization inside the spermatheca was investigated in two grasshoppers, (Scudder) and (DeGeer). The spermathecae were examined histologically from females whose copulations were interrupted at various prescribed intervals, either during their first or subsequent mating. Sperm organization inside the spermatheca from 24 to 120 hours after copulation had terminated was also investigated in . Scanning and transmission electron microscopy were used to investigate the distribution and morphology of small hair-like structures inside the spermathecae.<p> In both species sperm were first observed inside the spermatheca approximately 30 minutes after the initiation of copulation. The majority of sperm transferred into the spermatheca were in the form of sperm bundles, or spermatodesmes. In the rate at which sperm bundles were transferred appeared to decrease after 13 hours into copulation (average mating duration in the laboratory was 28 hours). In the rate of sperm transfer remained constant throughout copulation (average mating duration in the laboratory was 1.3 hours). The occurrence of both an abundance of individual sperm and sperm bundles was observed only in females of who had mated previously and had a second copulation of less than 9 hours in duration and in females of that had a second copulation less than 45 minutes in duration. As mating continued, fewer and fewer individual sperm were observed, and by 15 hours into copulation in only sperm bundles were observed inside the spermatheca. Therefore, it appears that the majority of the individual sperm in the above copulations are from prior matings, while most of the sperm bundles are from the last copulation. The interrupted matings of previously mated females indicate that at least some sperm bundles remain inside the spermatheca while individual sperm were removed by some mechanism, possibly sperm flushing by an excess of seminal fluid provided by the mating male.<p> In some sperm bundles remained intact for at least 7 days after the termination of copulation. The sperm bundles must disassociate into individual sperm prior to fertilizing the female's eggs, and therefore it may be the female that provides the mechanism or chemical stimulus to initiate sperm bundle disassociation prior to oviposition or prior to a second mating or both.<p> The results of this investigation suggest sperm competition, perhaps mediated by female choice, as a primary reason for lengthy copulations in . Male weight in has been documented to play a significant role in female choice and mating duration, whereas in , other factors such as nutrient transfer may play a significant role in female choice and mating duration. In , males may also act as mechanical plugs by remaining in copula for an extended time after a sufficient amount of sperm has been transferred, or males may be participating in the process of sperm removal by transferring an excess of seminal fluid to "flush-out" any sperm present from previous matings.<P>
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-19980330-170712 |
| Date | 01 April 1998 |
| Creators | Johnson, Jeffery Allan |
| Contributors | Marianne Niedzlek-Feaver, Lewis Deitz, Betty Black |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-19980330-170712 |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.0095 seconds