Ecological life history of Crangonyx pseudogracilis Bousfield (Crustacea: Amphipoda) in the Green Bottom Wildlife Management Area, Cabell County, West Virginia

Although the genus Crangonyx has been studied in the Appalachian area, most of this work has concentrated on subterranean species. A Crangonyx pseudogracilis population from the Green Bottom Wildlife Management Area (GBWMA), Cabell County, West Virginia was sampled weekly from March 1995 through July 1996 to investigate the ecological life history of the amphipod. A total of 1508 amphipods were collected. Amphipods were present in the study sites from November through July, at which time they migrated to deeper waters. Crangonyx pseudogracilis had a one year life cycle and bred from November to May. Adult amphipods began to die off in May and were gone by June. Males averaged 5.88 mm and females averaged 8.73 mm in length. There was no significant seasonal variation in sex ratio. Females produced several broods per year and ovigerous females were found from November 2 until May 8. They carried an average of 53.55 eggs and there was a low correlation between fecundity and length. The median tolerance limit (TLm) for low pH was 4.06, and a 96 hour laboratory test at this value produced a 65 percent survival rate. Plant detritus was the preferred food year round and comprised between 47 and 62 percent of the diet