Influence of temperature on puberty and maturation of pikeperch, Sander lucioperca.

Among external factors, temperature is known to exhibit a prominent role in reproduction of temperate fish species. Here, temperature related induction of puberty in pikeperch Sander lucioperca was investigated. For the first time the key factors of the pikeperch brain-pituitary-gonad axis, targeting the mRNA expression of the luteinising hormone (LH) and the follicle stimulating hormone (FSH), as well as the plasma sex steroids estradiol (E2), testosterone (T), 11-ketotestosteron (11-KT) and 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P) were addressed in the experiment. Concomitant the maturational stages were described histologically. After 3 months, female pikeperch kept at 12°C revealed significant increases in the GSI and plasma E2 concentration and 90% of the females were mid-vitellogenic. After 5 months, females kept between 9 and 15°C exhibited significant up-regulation of E2 and GSI as well as comparable histological outcome. At 6 and 23°C in nearly all females stagnation of oogenesis was recorded. Congruently, T was increased at 12 and 15°C. Expression analysis revealed a significant up-regulation of LHβ and FSHβ mRNA in females from early-vitellogenesis, and from mid-spermatogenesis in males, correlated to elevated plasma concentrations of steroids (except for E2 in males). In conclusion, moderate temperatures (12-15°C for) for at least 3 months were required to proceed with first maturation in juvenile pikeperch. The most efficient effect was observed at 12°C, while high (23°C) or low (6°C) temperatures prevented gonadal maturation. So temperature was identified as a prime factor in the induction of puberty in pikeperch, as revealed by histological as well as endocrine parameters.