Recombinant vs purified mammal gonadotropins as maturation hormonal treatments of European eel males
In the past three decades the European eel Anguilla anguilla experienced up to 99% decline in recruitment in some parts of its distribution range, thus breeding in captivity is nowadays considered key in order to save this species. With this in mind, obtaining high quality gametes is fundamental, as is the ongoing study of new hormonal treatments in order to improve current methods. Therefore, the aim of this research study was i) to assess the effect of two hormonal treatments (OVI, a recombinant α-choriogonadotropin; and VET, a human chorionic gonadotropin purified from female urine) on the reproductive performance of European eel males, and, after choosing the best hormone, ii) to compare the effects of three doses in order to cut the costs of artificial maturation.
Our results indicated that the type of hormone used (recombinant vs purified gonadotropins) significantly affected the progression of spermiation in European eel males, and that the recombinant hormone (OVI) produced better results in terms of sperm quantity and quality in most of the weeks of the treatment, remaining thus an effective treatment to induce spermiation in this species. On the other hand, in terms of the doses experiment, our results showed that from the lowest to the highest dose (0.25 to 1.5 IU/g fish) all the treatments were able to induce the whole spermiation process. However, a weekly dose of 1.5 IU/g fish of recombinant hormone (OVI) was necessary in order to provide a notable amount (volume and density) of high quality (motility and velocity) samples throughout the treatment.
Finally, the economic analysis demonstrated that the recombinant hormone (OVI, 1.5 IU/g fish) had a greater profitability than the other treatments, making it possible to obtain high-quality sperm for a lower price. In this context, and considering the fact that in the first few weeks of any hormonal treatment there is no high-quality sperm production, long-term hormonal therapies are necessary in order to lessen the cost of high-quality European eel sperm.