Thyroid Hormones and Their Influences on Larval Performance and Incidence of Cannibalism in Walleye Stizostedion vitreum¹

Abstract

Thyroid hormones, 3,5,3',5'tetraiodothyronine (T4) and 3,5,3'-triiodothyronine (TJ) have been found in the eggs of several teleost species and are potential regulators of larval development, growth, and survival. The purpose of the present study was to determine whether natural variation of TJ and T4 in the eggs of six stocks of walleye, five wild stocks from Kansas, Iowa, Wisconsin, Minnesota, and North Dakota, and a semidomesticated stock from an Ohio fish hatchery, have an effect on larval performance in mass culture. Immersion studies were conducted with samples of larvae from four of the same stocks at exposure concentrations of 0.01.0.05, and 0.1 ppm of T3 and T4. Natural egg concentrations of TJ (range from 0.70 to 1.5 ng/g wet weight of egg) were not significantly different among stocks. Although means of T4 concentration among stocks were significantly different (range 0.53-9.27 ng/g), the difference was caused by the exceptionally high concentration for the Wisconsin stock (9.27 ng/g f 2.20). Performance measures of the Wisconsin stock (Mississippi River), were not related to T4 concentration in that stock. In spite of similarity in concentrations of T4 and T3 in the eggs, there were significant performance differences among the stocks (survival to 21 d, gas bladder inflation, viability, cannibalism, and growth). The immersion studies, however, revealed a significant difference in incidence of cannibalism and temperature units (TU) to 50% mortality (i.e., survival) between the control groups and treatment groups exposed to 0.01 to 0.1 ppm T, and T4. Survival was extended more than 2-fold longer in larvae immersed in T3 compared with T4. The immersion study indicated that thyroid hormones are potentially regulators of walleye development, but further investigations are needed to determine reasons for differences in larval performance based on natural concentrations in the egg and artificial exposure (immersion).The thyroid hormones (TH), namely thyronine (3,5,3'-triiodo-L-thyronine, T,), and thyroxine (T4) have metabolic, structural, central nervous system, and behavior effects in vertebrates (Gorbman 1969). Of these two hormones, thyronine (T,) is considered to be the more active form (Eales 1985). Furthermore, studies have shown that thyroid hormones affect development and growth of larval fish (Brown et al. 1987).

The influence of triiodothyronine (T3) on the early development of piracanjuba (Brycon orbignyanus)

“…Kim and Brown (1997) demonstrated that the combination of thyroid hormones and cortisol reduced cannibalism and increased survival among larvae of Pacific threadfin (Polydactylus sexfilis) and suggested that a hormone-induced increase in uniformity of larval size could promote reduction in cannibalism. Differently, Hey et al (1996) found increased incidence of cannibalism in walleye exposed to thyroid hormones.…”

“…T 3 treatment of female fish also enhances egg quality and/or larval growth in several species by increasing hormone amounts in unfertilized eggs (Brown et al 1988(Brown et al , 1989Tachihara et al 1997). Furthermore, THs have been considered to reduce cannibalism in striped bass (Morone saxatilis) (Brown et al 1988) and matrinxã (Brycon cephalus) (Urbinati et al 2003) and increase cannibalism in walleye (Stizostedion vitreum) (Hey et al 1996). Exogenous THs have been also tested to improve hatchery production of some fish species (Brown et al 1989;Tachihara et al 1997;Stickney and Liu 1999).…”

Hatching success of walleye embryos in relation to maternal and ova characteristics

“…Thyroid hormones have been linked to both embryonic (Johnston et al 2005) and posthatch (Hey et al 1996) survival in walleye. The implications are that either the most limiting ova constituents were not examined in this study, or that the composition of the ova is not critical to embryonic survival to hatch, as long as minimum thresholds of nutrients are provided.…”

Clues from wildlife to create an assay for thyroid system disruption.

“…This stock was taken from "a highly contaminated river" and compared with the other three rivers (47). The authors did not discuss the nature of the contaminants.…”