Abstract
The standard method used to evaluate reproductive male fertility (Hafez, 2002) (in this case a bottlenose dolphin Tursiops truncatus) is semen analysis. In this case, some studies refer that the ejaculate has a big volume and contains an elevated number of spermatozoa with normal morphology and motility (Robeck, 2004).
An important aspect in this species is the seasonality, which refers to the period in which the reproductive events occur in a cyclic way, and that optimizes the seasonal changes of the environment to improve the survival of the species. Little research has been done in the reproductive seasonality of male cetaceans (Yuen, 2006). There are no reports of this topic in dolphins with the conditions of Mexico City.
Wild populations show that there is more variety in the reproductive season than in those individuals kept in captivity, but they still keep a high seasonality from their origin (Urian, 1996). There is not enough evidence to prove that sperm production is energetically expensive, which makes it hard to explain seasonality in males. Testicle size and testosterone production fluctuation usually show a direct influence in the male seasonality (Yuen, 2006), reflecting changes in fresh semen characteristics.
According to this, the knowledge acquired throughout the present study might be particularly useful to help us decide the best moment for semen collection and its later use in assisted reproduction.
This research was performed in the facilities of Convimar S.A. de C.V., at Aragon Aquarium in Mexico City, at 2240m above sea level, with a Tursiops truncatus male, approximately fifteen years old, and more than ten years in captivity.
Semen samples were collected manually once or twice a week using a positive reinforcement schedule combined with operant conditioning (Robeck, 2004, Soto, 2005), in a twenty one month period. Samples were analyzed with a 400x optic microscope and a semen analysis camera.
In the above graphics the lack of information means that the samples were azoospermic.
The results indicate that there was a fluctuation in the spermatic concentration during the period of twenty one months. The months with the highest concentration were from May to August, which makes them the most recommended months to collect semen samples. Therefore this study might be useful if this animal is used as a part in a reproductive program.
References
1. Hafez ESE, Hafez B. Reproducción e inseminación artificial en animales. 2002. Editorial McGraw Hill, 7th Edición.
2. Robeck TR, O´Brien JK. 2004, Effect of cryopreservation methods and pre-cryopreservation storage on bottlenose dolphin (Tursiops truncatus) spermatozoa. Biology of reproduction, 70, 1340-1348.
3. Soto R. Manejo reproductivo de delfines Tursiops truncatus en Convimar. 2005.. XXII Congreso Nacional de la Asociación de Zoológicos, Criaderos y Acuarios de México A.C. (AZCARM).
4. Urian KW, Duffield DA, Read AJ, Wells RS, Shell ED. 1996. Seasonality of reproduction in bottlenose dolphins, Tursiops truncatus. Journal of Mammalogy, 77(2):394-403.
5. Yuen QWH, Brook FM, Ying MTC, Kinoshita RE. 2006. Some evidence of seasonality in reproductive parameters of male indo-pacific bottlenose dolphins (Tursiops aduncus). 37th Annual Conference of the International Association for Aquatic Animal Medicine (IAAAM). Nassau, Bahamas.