FSH plasma levels during testicular recrudescence of precocious and non precocious male european sea bass using a newly developed species specific enzyme-linked immunosorbent assay (Elisa)

Abstract

Small fish displayed a remarkable delay in the progression of testicular development that prevented them from achieving spermiation in February. Large fish entered in spermatogonial mitosis towards meiosis in September, almost 1.5 month earlier than S group attaining full spermiogenesis in February. The highest FSH plasma levels were observed in L fish which almost doubled the FSH values of S fish at this time (p<0,05). These high levels of FSH were linked to spermatogonial proliferation and associated with the onset of gametogénesis, as in other teleost, [5]. A transient FSH peak (p<0.05) was observed at mid December in L fish coincident with increasing levels of LH suggesting a possible collaborative role of both gonadotropins in eliciting the 11KT surge observed at this time that in turn would drive active spermatogenesis forward and meiosis of germinal cells [2, 4,]. Finally, in L fish LH increased from mid October onwards peaking in February coinciding with full spermiation, revealing its prominent role at late gametogenesis. In S fish levels of LH were lower, started to increase one month later and peaked in February but with about half of the value shown by L fish at this date. In both groups 11-KT exhibited the highest levels by middle of December although values of L doubled those of S (p<0.05).In L fish a transient but significant elevation of 11KT was observed by the end of September coincident with the highest levels of FSH observed at this date, confirming the steroidogenic role of FSH in sea bass [6] and its mediation in stimulating early stages of spermatogenesis as previously suggested in other fish [5]. Though small fish had similar endocrine profiles as L fish, their amplitude were much lower being most likely the reason why functional competence of the BPG axis in former fish did not occur. Apparently fish size is a permissive condition to guaranty full effectiveness of the hormonal actions. The ELISA for sea bass FSH showed a high degree of parallelism between the standard curve and serially diluted plasma and pituitary samples of this species. The assay has a high sensitivity and reliability.