Induction of maturation and spermiation in the male European eel: assessment of sperm quality throughout treatment

Abstract

Weekly injections of human chorionic gonadotropin (hCG; 1·5 IU g 1 W) induced spermiation in 87-100% farmed male European eels Anguilla anguilla over a 10-week period, producing 3 ml (100 g) 1 milt volume, at 1·4 10 9 spermatozoa ml 1 sperm mobility peaked in ninth week of treatment with 97% of males with motile sperm. Gonadotropin-treated males showed earlier but similar morphological changes to control males. Whereas higher sperm density was obtained 6 h after hCG administration, higher percentage of motile cells and longer sperm mobility were observed 24 h after the treatment indicating that this is the optimum time to obtain good sperm after the hormonal induction. Several monounsaturated fatty acids in sperm increased significantly from week 5 to 9 of treatment (when highest volume, density and mobility of milt were recorded), whereas eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and total n-3 polyunsaturated fatty acids (PUFAs) were significantly reduced. Fatty acid levels returned to initial values after 13 weeks of treatment. These results are in agreement with the reduction of n-3 PUFAs recently observed in the ovary of female Japanese eel during artificial maturation, and an attempt is made to suggest a physiological explanation of its possible relation with sperm quality. 2000 The Fisheries Society of the British Isles

Subpopulation pattern of eel spermatozoa is affected by post-activation time, hormonal treatment and the thermal regimen

“…Sperm samples were collected weekly 24 h after administering the hormonal treatment, in order to 137 achieve the highest sperm quality (Pérez et al, 2000). Fish were anesthetized and the genital area was 138 cleaned with freshwater and thoroughly dried to avoid the contamination with feces, urine or sea water.…”

“…The 475 effectivity of gonadotropins to induce spermiation seems to be due to their LH-like effect and the 476 modulation of hypothalamic-pituitary-gonadal axis. Several studies have shown that the onset of 477 spermiation depends on a peak in LH plasma levels, which causes consecutive increases in androgen 478 synthesis and a shift to MIS production (Asturiano et al, 2000(Asturiano et al, , 2002. MIS have important effects in the 479 final phase of sperm maturation, causing sperm hydration and therefore an increase of its volume and 480 testicular size (Asturiano et al, 2002(Asturiano et al, , 2004 Peñaranda et al, 2010b).…”

Inducción hormonal de la espermiación y criopreservación de esperma en anguila europea (Anguilla anguilla).

“…Due to the fact that the eels do not mature sexually in captivity there have been developed methods for the hormonal induction that achieve the production of important volumes of sperm of good quality (Pérez et al 2000;Müller et al 2004). This fact has motivated the interest to develop techniques for the compilation and appropriate managing of the sperm of this species.…”

“…Con esto se pretendía optimizar tratamientos hormonales usados anteriormente y buscar tratamientos de inducción más cortos, con períodos más largos de producción de semen, menor manipulación de los peces y una mejor calidad del esperma. Los tratamientos fueron:• Tratamiento A: consistió en la administración semanal de 1.5 UI hCG/g pez durante 12 semanas (descrito previamente por Pérez et al 2000).• Tratamiento B: la dosis semanal de hormona suministrada a los peces fue de 0.75 UI hCG/g pez, equivalente a la mitad de la dosis del tratamiento A durante 12 semanas. …”

“…El resultado de la criopreservación depende de la calidad del semen extraído (estructura y crio-resistencia de los espermatozoides), así como de la composición físico-química del plasma seminal ya que el plasma presenta una alta variabilidad entre especies e individuos Pérez et al 2000;Asturiano et al 2001Asturiano et al y 2004a). …”