ISSN:
1432-136X
Keywords:
Sex steroids
;
Blood levels
;
Testicular in vitro secretion
;
Pubertal development
;
African catfish (Clarias gariepinus)
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Blood serum and testicular tissue samples were collected from 3 to 13-month-old African catfish (groups A-G) in order to study their pubertal development. The sampling covered the period from before the beginning of spermatogenesis until full maturity. Testes of fish in group A contained spermatogonia alone. In testes of group B, spermatogonia, spermatocytes and spermatids were present. Spermatozoa were first observed in group C and became predominant as the fish attained full maturity (group G). Several sex steroids were determined in the blood samples. Testosterone was the quantitatively dominating androgen in the blood serum (3–5 ng·ml-1) in groups B and C (fish in group A were too small to collect blood samples). In group D, the concentrations of 11-ketotestosterone and 11β-hydroxyandrostenedione increased to levels similar to those of testosterone. Androstenedione that was undetectable before (below 0.4 ng·ml serum-1), also increased to 3–5 ng·ml-1 in group D. The levels of androgens kept increasing until the fish attained full maturity (group G). In order to monitor the responsiveness to gonadotropic hormone and the steroid secretion capacity, the in vitro secretion of two steroids (11β-hydroxyandrostenedione and 17α,20β-dihydroxy-4-pregnen-3-one) by testicular tissue was quantified at the different stages of development. Testicular maturation was accompanied by changes of both the steroid secretion capacities and of the sensitivity to gonadotropic hormone. The most important changes occurred just after the initiation of spermatogenesis, as spermatocyte/spermatid formation was associated with a drop of the secretory capacity (amount of steroid secreted per milligram of tissue incubated) and with a reduced sensitivity to gonadotropic hormone. At later stages, when the testicular weight substantially increased concurrently with the formation of numerous spermatozoa, both the secretory capacity and the responsiveness to gonadotropic hormone increased again to reach the levels typical of adult fish. The blood levels of androgens appeared to be positively related to the increasing testicular weight in the later phases of development.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00354080
