chapter 3 - RiuNet

GENERAL DISCUSSION
profiles induced by each thermal treatment (Peñaranda et al., in
preparation).
After selecting the best thermal regime (T20), the kind of hormone used for
the induction of maturation was chosen as the second factor for the
improvement of reproductive performance. Although successful maturation
and spermiation by hCG has been reported by several authors in the last
half century (Boëtius and Boëtius, 1967; Bleniarz and Epler, 1977; Amin,
1997), scarce attempts have been made to optimize previously used
hormonal treatments (Asturiano et al., 2005). Our results have shown that
the type of hormone used significantly affects the onset and progression of
spermiation in European eel males, and a recombinant version of the hCG
(hCG rec ) produces the best results in almost all the sperm parameters.
Until the present study, only Asturiano et al. (2005) had carried out trials
with the aim of achieving shorter induction treatments, longer spermiation
periods and/or higher sperm quality. In their experiment, five hormonal
treatments based on hCG, modifying both the doses and timing of injection,
were tested for the induction of maturation and spermiation in male
European eels, reaching a good reproductive performance. Even so, the
results produced by the hCG rec treatment in the present trial far exceed
those reached by Asturiano et al. (2005), thus making it an effective and
alternative treatment for inducing spermiation in male European eels.
To sum up, a new hormonal treatment which improves the reproductive
performance of male European eels has been set up and is ready for
applying in eel hatcheries. This treatment, based on the weekly
administration of hCG rec under a constant temperature regime of 20 °C, has
been able to induce a high percentage of spermiating males with good
quality samples for a high number of weeks. In addition, other tools such as
short and long-term sperm storage methods have specifically been
developed for this species in recent years (Peñaranda et al., 2008, 2009,
2010). With regards to short-term sperm storage methods, recent studies
have come up with good results in terms of fertilized eggs and hatched
larvae during in vitro fertilization trials. However, although it was possible
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