Meeting Abstract

35.3  Friday, Jan. 4  Short term tolerance to changes in environmental salinity by the longhorn sculpin, Myoxocephalus octodecimspinosus . HYNDMAN, Kelly/A*; EVANS, David/H; Univ. of Florida, Gainesville; Mount Desert Biological Laboratory, Maine khyndman@zoo.ufl.edu

The bottom-dwelling longhorn sculpin, Myoxocephalus octodecimspinosus, is a marine fish that fisherman have found in estuaries during high tide, suggesting that they can tolerate short term exposure to dilute environments. Little is known about the salinity tolerance of sculpin, thus the purpose of these experiments were to determine if sculpin can tolerate short term exposure to hypoosmotic environments, and the effects on plasma osmolality and ions, and gill Na+, K+-ATPase (NKA), Na+, K+, Cl- cotransporter (NKCC) and cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and protein levels. Sculpin were acclimated to either 10%, 20% or 100% seawater for 24 or 72 hours, at which point, blood and gill samples were taken. Total plasma osmolality, sodium, potassium and chloride concentrations were not different between the 20% and 100% treatments. Also, NKA activity and protein levels did not differ between these two treatments. Acclimation for 24 hours to 10% SW decreased plasma osmolality, Na+, K+ and Cl- levels ~15% compared to the 100% SW treatment and decreased ~25% with 72 hours of 10% seawater acclimation. The effects of hypoosomotic acclimation on NKA, CFTR and NKCC, mRNA and protein levels will be discussed. These results suggest that down to 20% seawater, sculpin are capable of completely regulating ion levels over a 72 hour period. With 10% seawater exposure, there is a decrease in plasma total osmolality and ions, and these values match levels for freshwater teleosts. This ability to regulate plasma osmolality over 4 days during hypoosomotic stress demonstrates they are capable of entering estuaries and exploring new niches. The genus Myoxocephalus has three freshwater species, and it may be this salinity tolerance in the marine sculpin that initially led to their invasion of fresh water.