Thiamine and fatty acid content of walleye tissue from three southern U.S. reservoirs

Maternal influences on thiamine status of walleye Sander vitreus ova

Concentrations of the various forms of thiamine (vitamin B(1) ) were determined in walleye Sander vitreus ova from three central North American lakes. Total thiamine concentrations in ova from Lake Winnipeg S. vitreus were approximately three times greater (mean 12 nmol g(-1) ) than in those from Lakes Erie or Ontario. The percentage of thiamine in the active form (thiamine pyrophosphate, TPP) was highest in Lake Ontario ova (mean 88%) and lowest in those from Lake Winnipeg (mean 70%). Neither ova total thiamine concentration nor per cent ova thiamine as TPP showed any consistent relationships with maternal age, size, morphometric condition, somatic lipid concentrations or liver lipid concentrations. Ova total thiamine concentration, however, was negatively related to ovum size in some populations, as well as among populations, and was positively related to liver total thiamine concentration. Maternal transfer of thiamine to ova appears to be independent of female ontogenetic or conditional state in S. vitreus.

Variations of thiaminase I activity pH dependencies among typical Great Lakes forage fish and Paenibacillus thiaminolyticus

The source of thiaminase in the Great Lakes food web remains unknown. Biochemical characterization of the thiaminase I activities observed in forage fish was undertaken to provide insights into potential thiaminase sources and to optimize catalytic assay conditions. We measured the thiaminase I activities of crude extracts from five forage fish species and one strain of Paenibacillus thiaminolyticus over a range of pH values. The clupeids, alewife Alosa pseudoharengus and gizzard shad Dorosoma cepedianum, had very similar thiaminase I pH dependencies, with optimal activity ranges (> or = 90% of maximum activity) between pH 4.6 and 5.5. Rainbow smelt Osmerus mordax and spottail shiner Notropis hudsonius had optimal activity ranges between pH 5.5-6.6. The thiaminase I activity pH dependence profile of P. thiaminolyticus had an optimal activity range between pH 5.4 and 6.3, which was similar to the optimal range for rainbow smelt and spottail shiners. Incubation of P. thiaminolyticus extracts with extracts from bloater Coregonus hoyi (normally, bloaters have little or no detectable thiaminase I activity) did not significantly alter the pH dependence profile of P. thiaminolyticus-derived thiaminase I, such that it continued to resemble that of the rainbow smelt and spottail shiner, with an apparent optimal activity range between pH 5.7 and 6.6. These data are consistent with the hypothesis of a bacterial source for thiaminase I in the nonclupeid species of forage fish; however, the data also suggest different sources of thiaminase I enzymes in the clupeid species.

Linking egg thiamine and fatty acid concentrations of Lake Michigan lake trout with early life stage mortality

The natural reproduction of lake trout Salvelinus namaycush in Lake Michigan is thought to be compromised by nutritional deficiency associated with inadequate levels of thiamine (vitamin B1) in their eggs. However, mortality driven by thiamine deficiency (commonly referred to as early mortality syndrome [EMS]) is not the only significant cause of low lake trout survival at early life stages. In this study, we sought to better understand the combined effects of variable levels of thiamine and fatty acids in lake trout eggs on prehatch, posthatch, and swim-up-stage mortality. We sampled the eggs of 29 lake trout females from southwestern Lake Michigan. The concentrations of free thiamine and its vitamers (e.g., thiamine monophosphate [TMP] and thiamine pyrophosphate [TPP]) as well as fatty acid profiles were determined in sampled eggs. Fertilized eggs and embryos were monitored through the advanced swim-up stage (1,000 degree-days). Three distinct periods of mortality were identified: prehatch (0-400 degree-days), immediately posthatch (401-600 degree-days), and swim-up (601-1,000 degree-days). Stepwise multiple regression analysis revealed (1) that cis-7-hexadecenoic acid in both neutral lipids (NL) and phospholipids (PL) correlated with prehatch mortality, (2) that docosapentaenoic acid in PL and docosahexaenoic acid in NL correlated with posthatch mortality, and (3) that total lipids, TPP, and palmitoleic acid in NL, linoleic acid, and palmitic acid in PL correlated with the frequency of EMS. These results indicate the complexity of early life stage mortality in lake trout and suggest that inadequate levels of key fatty acids in eggs, along with variable thiamine content, contribute to the low survival of lake trout progeny in Lake Michigan.