Seasonal changes in serum testosterone, 11-ketotestosterone, and 17β-estradiol levels in the brown bullhead, Ictalurus nebulosus Lesueur

Abstract

The seasonal changes in gonadosomatic index (GSI) and serum testosterone, 11-ketotestosterone, and 17β-estradiol levels were measured in adult feral brown bullheads, Ictalurus nebulosus Lesueur. The maximum GSI of both male and female brown bullheads was considerably lower than that of most other teleostean species investigated. In males, the GSI began to increase in April concomitant with an increase in water temperature from 3 to 6 °C. The maximum GSI levels were evident throughout May and June (during the prespawning and spawning periods). Peaks of serum testosterone and serum 11-ketotestosterone levels were evident in mid-April and late May to June, and in mid-April and mid-May, respectively. In females there was a rapid increase in GSI during May, when the ambient water temperature reached 16 °C. The peak GSI was evident in mid- to late-May and had declined by early June. Peak serum testosterone and 11-ketotestosterone levels were evident in mid-April and again in late May, whereas peak 17β-estradiol levels were found in mid-May and mid-June. The peak serum testosterone levels in females were 4.5-fold higher than in the males, whereas the 11-ketotestosterone levels were similar in males and females.

Seasonal changes in steroid metabolism in the male reproductive organ-system of the African catfish, Clarias gariepinus

“…Although in the testes of the Indian catfish, Heteropneustes fossilis, interstitial cells were not prominent during the period of active spermatogenesis and the ensuing breeding period (Nayyar and Sundararaj, 1970)) a correlation between plasma testosterone elevation and growth of testes and seminal vesicles was found by Lamba et al (1983). A similar correlation was observed in Ictalurus nebulosus (Burke et al, 1984). Testosterone, however, is hardly formed in testes of Chrias guriepinus during the reproductive cycle.…”

Croissance ovocytaire et régulation stéroïdienne chez les poissons à pontes unique et multiples : une revue

“…3) reflètent probablement l'incorporation rapide du PPP dans les ovocytes (Rinchard 1996, Rinchard et al 1997). Ce type de profil bimodal de l'E2 est également observé chez d'autres espèces, comme chez le poisson-chat, Ictalurus nebulosus LeSueur (Burke et al 1984), la dorade royale, Spams aurata L. (Kadmon et al 1985), le Morone americana Gmelin. (Jackson & Sullivan 1985) A la fin du cycle sexuel, principalement avant la maturation finale et l'ovulation, la concentration en oestrogènes chute (Wingfield & Grimm 1977, MacGregor et al 1981, Singh & Singh 1990).…”

“…Enfin, chez le flétan, Methven et al (1992) constatent que l'E2 atteint sa concentration la plus élevée juste avant le frai et qu'une baisse soudaine précède la première ponte. Par la suite, les différentes fluctuations d'E2 sont mises en relation avec le développement successif des différents lots d'ovocytes, tout comme cela a été montré chez le poisson-chat Ictalurus punctatus Rafinesque (Burke et al 1984), le carassin doré (Kobayashi et al 1988) et le fondule Fundulus grandis Baird & Girard (Greeley et al 1988).…”

“…3) Prat et al 1990, Rinchard et al 1993). Toutefois, chez certaines espèces, comme le poissonchat Ictalarus punctatus (Burke et al 1984), le doré jaune (Malison et al 1994), le bar commun (Prat et al 1990), le gardon (Rinchard et al 1997), deux pics distincts de T ont pu être observés au cours du cycle reproducteur annuel. Le premier pic correspond généra-lement à la reprise de la vitellogenèse et l'augmentation rapide de la concentration d'E2.…”

“…Toutefois, chez les pondeurs multiples, la concentration en T se maintient à des teneurs élevées puisqu'elle sert de précurseur à l'E2 , Burke et al 1984, Kobayashi et al 1988, Prat et al 1990, Methven et al 1992, Rinchard et al 1993). …”