OSMOREGULATION AND SALINITY TOLERANCE IN THE FRESHWATER CRAYFISH ORCONECTES RUSTICUS

Abstract

The presence of Orconectes rusticus in Maryland tributaries of the Chesapeake Bay was first documented in 2007. Orconectes rusticus alters freshwater ecosystems by displacing native species and clearing sub-aquatic vegetation, but the capacity for this species to invade the estuarine waters in the Chesapeake Bay is presently unknown. Adult 0. rusticus were subjected to a range of salinities to establish preliminary data on their invasion potential into the Chesapeake Bay. The 4-week trial included treatments of 1, 7, 14, 21 and 28 psu. Orconectes rusticus had 70% or greater survival up to 21 psu. Haemolymph osmolarity was also measured in adult 0. rusticus in 21 psu over a time series. Osmolarity increased at each time-point and was nearly isosmotic to the medium on Day 9. This data suggests that adult 0. rusticus would be able to tolerate salinities found in the upper Chesapeake Bay.