Specific recombinant gonadotropins induce spermatogenesis and spermiation by first time in a teleost fish, the European EEL

Abstract

Eel recombinant gonadotropins have induced spermatogenesis in vitro, but had limited effect in vivo. New specific single-chain recombinant gonadotropins (Rara Avis Biotec S.L.) were tested treating European eel males with rFSH and rLH. Males received rFSH in three doses (2.8, 1.4 and 0.7 ¿g/fish; high, medium and low treatments) during 3 weeks. Later, an increasing rLH dose (every 3 weeks; 1, 2, 6 ¿g/fish) was combined with rFSH. Three males/treatment were sacrificed every 3 weeks. Blood and testis samples were taken for steroids and histological analyses and GSI was calculated. Sperm quality was determined by CASA software. rFSH by itself was able to induce the spermatogenesis (week 3), causing higher androgen levels and development until the spermatogonia 2 stage in the high rFSH group. The rLH (week 6) promoted further maturation to spermatocyte 2 stage in the medium and high groups, but no gonadal progression was observed in the low group. Higher T levels were reached in all the groups, and the biggest 11KT values in the rFSH high group. A second increase of rLH (week 9) induced further maturation to spermatid-spermatozoa 1 and spermatocyte 1 stages in the high and low groups, respectively. The medium group showed no further maturation (spermatocyte 1-2 stages). The highest dose of rLH (week 12) induced the most advanced stage (spermatozoa 2), and significant GSI increase in all the groups. A progressive 11KT (high group) and T (all treatments) decrease was observed from week 9 to 12. All treatments induced spermiating males, however, the best sperm quality with ?50% motile cells and volumes ~0.4 ml was observed in males treated with the highest rFSH dose and a progressive increase of rLH treatment. On the other hand, a 20% of nonresponders were observed and the sperm quality was variable. So, further experiments are required to improve these treatments.