Meeting Abstract

P2.137  Sunday, Jan. 5 15:30  Novel osmolyte in Atlantic salmon (Salmo salar) as a potential biomarker of freshwater-seawater transition ZAJIC, D.E.*; CRAMB, G.; GOTZ, M.; VILLASENOR, A.; YANCEY, P.H.; Whitman College; Univ. of St. Andrews; Whitman College; Whitman College; Whitman College zajicde@whitman.edu

Organic osmolytes are small solutes that increase osmolality inside cells to stop osmotic water loss without disturbing cellular functions and, in some cases, to stabilize proteins against denaturants like urea, salt and pressure. In recent years, some euryhaline teleosts, which as osmoregulators have been thought not to use such osmolytes, have been found to accumulate them in many tissues following freshwater (FW) to seawater (SW) acclimation. The current study was undertaken to examine the osmolyte profile of Atlantic salmon (Salmo salar). High-performance liquid chromatography identified osmotically significant levels of taurine and an unknown compound in fins and skin of S. salar, at levels (from highest to lowest) in: juveniles (6 mo old) acclimated 3 wks in SW > young adults (9 mo old) acclimated 3 mo in SW > juveniles (6 mo old) in FW > adults (30 mo old) kept 2 yrs in SW. Currently, gill Na/K-ATPase levels are measured at salmon farms to determine when S. salar should be moved from FW to SW. We suggest this unknown osmolyte might serve as a biomarker for the salmon industry as indicator of readiness for FW to SW transition. Nuclear magnetic resonance has tentatively shown the unknown compound as a possible di- or tri-peptide, perhaps containing isoleucine. Small peptides have only rarely been found to be osmolytes, and this would be the first known to contained isoleucine. Common osmolytes such as alanine, glutamine and proline were also observed to be highest in juvenile SW fish, though a complete age survey must be completed to ensure each compound’s role as potential osmolytes and biomarkers. Funding: Whitman College and Natural Environment Research Council.