Effect of different methods for the induction of spermiation on semen quality in European eel

Abstract

Five hormonal treatments with human chorionic gonadotropin (hCG) were tested for the induction of maturation and spermiation in male farmed eels. The main aim was to optimize previously used hormonal treatments to achieve shorter induction treatments, longer spermiation periods and/or higher sperm quality. Fish treated for just 3 weeks (treatment E) or until the onset of spermiation (treatment C) showed the worst results, while the treatment consisting of weekly administration of 1.5 IU hCG g À1 ¢sh (treatment A) induced the highest percentage of spermiating males, the highest number of sperm samples and sperm volumes and densities similar to the rest of the treatments (B: half hormone dosage, or D: biweekly administration). Evaluation of the sperm quality was performed by computer-assisted sperm analysis (CASA), considering the percentage of total motile spermatozoa, the percentage of fast and medium-velocity spermatozoa, as well as di¡erent motility parameters. Sperm samples from A-D groups showed between 44% and 54% motile spermatozoa, and between 10% and 15% fast spermatozoa, while samples from E-treated males showed 0% motile cells. No signi¢cant di¡erences were found in the spermatozoa straight line velocity (VSL), curvilinear velocity (VCL) or the angular velocity (VAP), neither spermatozoa beating cross frequency (BCF) between A^D groups.

Roles of lipids and fatty acids through the spermatogenesis of European eel (Anguilla anguilla)

“…We used data from Gallego et al (2012), who registered sperm volumes similar to those described by other authors (1-4 mL 100 g fish −1 ; (Pérez et al, 2000;Asturiano et al, 2005) and, an increasing trend in sperm volume over the weeks of spermiation. Regarding the correlations found between sperm volume and the fatty acids present in the different tissues, significant correlations with the liver fatty acids were found.…”

“…The sexual maturation of males can be induced by using long-term hormonal treatments (Ohta et al, 1997;Pérez et al, 2000;Asturiano et al, 2005;Huang et al, 2009;Gallego et al, 2012). The effect of different hormonal treatments and environmental parameters on gamete quality has been studied in both Japanese and European eels (Miura et al, 1991;Asturiano et al, 2005;Gallego et al, 2012;Mazzeo et al, 2012) but the effect of broodstock feeding on gamete quality has been investigated in female eels (Furuita et al, , 2007Ozaki et al, 2008;Oku et al, 2009;Støttrup et al, 2012), not in males.…”

“…To date, eels do not mature spontaneously in captivity, so the sexual maturation of males must be induced using long-term hormonal treatments (Asturiano et al, 2005;Gallego et al, 2012;Huang et al, 2009;Ohta et al, 1997;Pérez et al, 2000).…”

Molecular approaches related to the European eel (Anguilla anguilla) reproductive process

“…So, in captivity, eels are blocked in a pre-pubertal stage and do not spontaneously mature (Dufour et al, 2003;Montero et al, 1996). To induce sexual maturation and gonadogenesis it is necessary to use chronic hormonal treatments, usually weekly injections of carp/salmon pituitary extract for females (Asturiano et al, 2002, Fontaine et al, 1964Pedersen, 2003) and weekly injections of human chorionic gonadotropin (hCG) for male eels (Asturiano et al, 2005;Boëtius and Boëtius, 1967;Gallego et al, 2012;Huang et al, 2009;Ohta et al, 1996Ohta et al, , 1997aPérez et al, 2000).…”

“…However, as detailed information from the field is still lacking, it is difficult to simulate the variable environmental factors which would occur during the migration (temperature, photoperiod, pressure, etc). That is why, in captivity, silver eels are blocked in a prepubertal stage (Dufour et al, 2003;Pasqualini et al, 2004;Vidal et al, 2004) and must receive a long-term hormonal treatment to induce sexual maturation and spermiation (Boëtius and Boëtius, 1967;Ohta et al, 1996Ohta et al, , 1997aAsturiano et al, 2005;Huang et al, 2009;Pérez et al, 2000;Gallego et al, 2012).…”