Meeting Abstract

22.4  Tuesday, Jan. 4  The influence of host physiology and infection intensity on the metamorphosis of freshwater mussel larva. DUBANSKY, B*; WHITAKER, B; GALVEZ, F; Louisiana State University, Baton Rouge, LA bduban1@lsu.edu

The larva of unionid freshwater mussels (glochidia) undergo a parasitic stage requiring their attachment to the external epithelia of fish hosts, where they metamorphose into free-living juveniles. We have previously shown that bluegill sunfish (Lepomis macrochirus) undergo a classical stress response when infected with glochidia from the paper pondshell (Utterbackia imbecillis) at concentrations at or greater than 2000 larva per liter. Hosts experiencing an elevation in plasma cortisol had a 52% increase in the number of attached glochidia per gram fish, and an increase of 31% in attached glochidia successfully metamorphosing into free-living juveniles. In order to determine whether alterations in host physiology may be influential in the successful metamorphosis of glochidia on fish, bluegill sunfish were first given an intraperitoneal injection of cortisol to chronically elevate plasma cortisol, then infected within two days with glochidia from the paper pondshell at 1000 glochidia per liter. Cortisol-injected fish showed a 42% increase in the number of attached glochidia per gram fish, and 28% increase in glochidia metamorphosis success compared to sham-injected and control fish. Current studies are investigating the physiological basis in the host governing alterations in glochidia attachment and metamorphosis success. This research will provide insights into the influence of host physiology on glochidial attachment and juvenile mussel transformation. This work was funded by the Louisiana Board of Regents IRC subprogram and the Louisiana Department of Wildlife and Fisheries.