Changes in Na+-K+, ATPase Expression and Activity in the Blue Crab

Callinectes sapidus in Response to an Increase in Environmental Salinity

Stacey Novello, Biology

Faculty Mentor: Dr. Donald Lovett

              The blue crab Callinectes sapidus lives in an estuarine environment and must be able to adapt to the changing salinity of the seawater in this habitat.  The crab adjusts to this changing salinity through osmoregulation, the maintenance of a constant blood salinity.  Osmoregulation takes place mainly in the crab’s gills via an enzyme called Na+,K+-ATPase.  Na+,K+-ATPase actively pumps salt from the surrounding seawater into the crab’s blood.  This summer we have been studying how the gene expression and activity of Na+,K+-ATPase is affected when a crab is transferred from a low salinity environment to a high salinity environment.  We have studied crabs that were acclimated to low salinity and were then transferred to high salinity seawater for varying time periods ranging from 12 hours to 18 days. In order to study these changes, we first extracted and homogenized gill tissue from the crab.  The RNA content and enzyme activity of each sample were then analyzed.  The RNA samples were reverse transcribed and the DNA was then amplified using primers specific for the gene coding for Na+,K+-ATPase.  In order to measure the expression of this gene we used quantitative polymerase chain reactions.  The enzyme activity was measured using a spectrophotometer in order to determine the activity level of the enzyme through the comparison of two samples, one with the Na+,K+-ATPase inhibitor ouabain, and one without the inhibitor.  We hope to determine the specific effects of the transfer from a low salinity to a high salinity environment on the expression and activity of Na+,K+-ATPase and over what time period these changes take place.

Personal Statement

              This experience with summer research has been very valuable to me because it has allowed me to get first hand practice with real scientific techniques and procedures.  It has provided me with a better look at what it means to do real research and has allowed me to personally contribute to the ever growing body of scientific knowledge.  These are experiences that one cannot gain from just passively learning about biology in the classroom.  It has also allowed me to gain helpful insight into what I would like to do after completing my undergraduate degree.  In addition to the academic opportunities the SURP program has made available to me, it has also allowed me to interact with the faculty on a more personal level through weekly breakfasts and the occasional barbeque.