Length and duration,… these are important parameters for sexual success. That refers not only to the sexual act itself but also to the sperm traits. Longer and faster spermatozoa with longer life-duration are expected to have an advantage in competitive interactions between ejaculates. However, there is little evidence for this sperm competition theory. The sperm competition theory claims that (I) increasing sperm competition leads to faster spermatozoa and (II) this increase of speed is related to an increase in sperm length. However, both, that sperm competition promotes evolution of faster-swimming sperm across species, and link between sperm morphology and swimming speed, is weakly supported by just a handful of studies and even neglected by other studies. For example: the only clear evidence for the length-speed correlation of sperm within a species comes from the roundworm C.elegans and its sperm has, unlike the sperm of the most animals, an amoeboid form (lacking a flagellum). In order to prove that theory, species are needed which relatedness are well studied and which show a high diversity of mating behaviour, like the cichlid fishes of the Lake Tanganyika. Therefore, John L. Fitzpatrick et al. (2009) tested the sperm competition theory in 29 closely related species of cichlid fishes from Lake Tanganyika. They proved both hypotheses of the sperm competition theory by slitting fish testes and comparing sperm traits across the species (inside a species proof of the hypotheses mainly failed). They showed that:
"Female promiscuity promotes the evolution of faster sperm in cichlid fishes".
John L. Fitzpatrick, et al. Proceedings of the National Academy of Sciences 106.4 (2009): 1128-1132.
0 Kommentare
Hinterlasse eine Antwort. |
IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
Kategorien
Alle
|