Nuestro último artículo, aceptado en Reproduction, Fertility and Development

The subpopulation pattern of eel sperm is affected by post-activation time, hormonal treatment and thermal regime

V. Gallego, M.C. Vílchez, D.S. Peñaranda, L. Pérez, M. P. Herráez, J.F. Asturiano, F. Martínez-Pastor

Natural stocks of eels (genus Anguilla) have suffered a dramatic reduction in the last 60 years, and the culture of eels is still based in the capture of very large quantities of juveniles. It is necessary to close the life cycle in captivity in order to lift the pressure on wild populations. Our aim has been to evaluate sperm subpopulations (through cluster analysis of computer-assisted sperm analysis -CASA- data) in European eel (Anguilla anguilla), and assess the effects of motility-acquisition time post-activation: 30, 60 and 90 s; thermal regimes: 10 ºC (T10) or 15 ºC (T15) and up to 20 ºC, or constant at 20 ºC (T20); and hormonal treatments: human chorionic gonadotropin (hCG), recombinant (hCGrec) or pregnant mare serum gonadotropin (PMSG). In all cases, we obtained three subpopulations: low velocity and linearity (S1), high velocity and low linearity (S2) and high velocity and linearity (S3, considered high-quality).

Total motility and S1 were affected by acquisition time, thus 30 s is recommended as the standard time for motility acquisition. When animals were kept at 20 _C (T20), motility data fitted quadratic models, with the highest motility and proportion of S3 between weeks 8 and 12 after the first injection. Lower temperatures (T10, T15) delayed spermiation and obtaining of high-quality sperm (S3), but did not seem to alter the spermiation process (similar subpopulation pattern). On the other hand, the hormonal treatments altered both the dynamics of the subpopulation pattern and the onset of spermiation (with PMSG delaying it). Total motility and the yield of S3 using the widely used hCG varied throughout the spermiation period. However, hCGrec allowed us to obtain high-quality and constant motility for most of the study (weeks 7 to 20), and the S3 yield was also higher overall (61.8%±1.3) and more stable over time than the other hormonal treatments (averaging 53.0%±1.4). Using T20 and hCGrec would be more economical and practical, allowing us to obtain a higher number of S3 spermatozoa for an extended time.