EEB Seminar

Dr. Zeeshan Syed (Syracuse University)

Sperm-looping: A spermatogenic novelty

March 25th 12:30-1:30pm ET

Looped spermatid of D. willistoni

Post copulatory sexual selection (PCSS) is often responsible for rapid coevolution of male and female reproductive traits, resulting in co-diversification of those traits traits among species. One of the more dramatic examples of such co-diversification is the evolution of sperm length and female seminal receptacle length across diverse taxa including Drosophila. The female reproductive tract is the selective environment for sperm where there’s a strong selection on sperm length for competitive fertilization success. However, the cost for producing long sperm is in increased investment in producing long testes, often leading to extended time to reach sexual maturity. All Drosophila species studied so far have testes longer than the sperm they manufacture. 

We discovered an exception to this rule in the members of the willistoni and saltans species groups. They represent an independent evolutionary origin of long sperm and long SR. However, the males are able to produce long sperm in much shorter testis through the innovation of sperm looping. In this talk, I would discuss the evolutionary costs and adaptive benefits of this phenomenon that we have figured out so far, as well as some unanswered questions that we are currently trying to address. 

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