Rapid and extensive genetic introgression has occurred between Pecos pupfish (Cyprinodon pecosensis) and sheepshead minnow (Cyprinodon variegatus) in the wild. We studied both female mate choice and male-male competition for mates among C. pecosensis, C. variegatus, and their F1 hybrids to determine what role these behaviours played in the formation of the hybrid swarm. Female C. pecosensis pre...

Age-0 yellow perch (Perca flavescens) were collected during October 1998 and age-1 yellow perch were collected during June 1999 from southeastern Lake Michigan off St. Joseph and Muskegon, Michigan, to evaluate diets relative to recent ecosystem changes. Size range of yellow perch examined was 72 to 118 mm. In October at a 15-m site off Muskegon, both Gammarus spp. and Isopoda were found in nea...

SUMMARYVertically transmitted parasites may have positive, neutral or negative effects on host fitness, and are also predicted to exhibit sex-specific virulence to increase the proportion or fitness of the transmitting sex. We investigated these predictions in a study on the survival and sex ratio of offspring of the amphipod Gammarus roeseli from females infected by the vertically transmitted ...

The purpose of this toxicity test was to determine the reliability and comparability of Cu++ toxicity on Gammarus fasciatus. The study was conducted to compare toxicity results for Rainbow trout, Salmo ~airdneri Richardson, another coldwater poikilotherm. Since G. fasciatus comprises a major portion of the diet of many freshwater fishes, it can be stated to be an "important" species (PATRICK et...

Inland epigean freshwater amphipods of Romania are diverse and abundant for this region has a favourable geographical position between the Balkans and the Black Sea. Excluding Ponto-Caspian species originating in brackish waters and freshwater subterranean taxa, there are 11 formally recognized epigean freshwater species recorded from this country. They belong to 3 genera, each representing a d...

marine ecosystem pollution is one of the important problems of today environment. in this study the existence of heavy metal in the namrood river, situated in firoozkooh in tehran province, iran has been investigated. the namrood river is located near firoozkooh route, and is affected by pollutant from tourist centers, entertainment, gas stations, nearby villages’ sewage systems, farming efflue...