Potential sources of thiaminase causing thiamine deficiency complex (TDC) in Great Lakes salmonines

Session: Thiamine Deficiency in the Great Lakes (2)

Catherine Richter, CERC, USGS, [email protected]
Allison Evans, Oregon State University, [email protected]
Donald Tillitt, U.S. Geological Survey, Columbia Environmental Research Ctr., [email protected]

Abstract

Thiamine (vitamin B₁) metabolism is an important driver of ecological health. Thiamine is an essential co-factor for energy metabolism enzymes and is required by all organisms. Competition for thiamine has resulted in evolution of diverse strategies for thiamine synthesis, uptake, salvage, and degradation. Some organisms, including species of ferns, molluscs, and fish, contain thiamine-degrading enzymes known as thiaminases, and consumption of these organisms can lead to thiamine deficiency (TDC) in the consumer. In the Great Lakes, low thiamine leads to elevated early life stage mortality prior to initiation of exogenous feeding in native Lake Trout (Salvelinus namaycush) populations that consume the non-native prey fish Alewife (Alosa pseudoharengus), thus, impeding goals for Lake Trout rehabilitation. Investigating the ultimate source of thiaminase in Lake Trout diets, we compare evidence for thiaminase produced by bacteria with evidence for thiaminase produced de novo by fish, and conclude that thiaminase produced by Alewife is the major source of thiaminase activity in Lake Trout diets in the Great Lakes. Therefore, management actions that reduce the proportion of Alewife in the diet of Lake Trout or reduce production of thiaminase by Alewife may result in increased thiamine concentrations in Lake Trout eggs.