To do so, the scientists studied waters in the Mobile River Basin in the southeastern United States, a 113, 000 square kilometer area with 34 dams distributed in the area. To rule out natural differences in physique, the more common the farther the populations are geographically apart, the researchers studied only fish from adjacent rivers and reservoirs. From their living in running waters conspecifics located in reservoirs fish differed in several points: Particularly striking was the smaller head of the fish from the reservoir and their narrower body in contrast to the wider river fish. In addition, the dorsal fin was further forward on the body and was also much shorter at the base. The eyes were a bit lower and more in the direction of the belly. In addition, the scientists found a relationship between the size of the reservoir and the size of Cyprinella venusta.
For the researchers, the changes in body morphology are a direct response to the new environment. They suggest that damming water has put a lot of evolutionary pressure on aquatic life. The changes in body shape have a direct impact on the fitness of the fish. For example, the changes identified by the researchers as morphological shifts affect, for example, the nature of the movement of the aquatic inhabitants. Also, changes in the prey populations may be a trigger for physical transformation.Travis Haas (Tulane University, New Orleans) et al .: Proceedings of the Royal Society, online pre-release, doi: 10.1098 / rsbl.2010.0401 ddp / science.de? Gwydion Brennan ad