Sperm Cryopreservation in Brown Bear (Ursus arctos): Preliminary Aspects

Abstract

The development of sperm cryopreservation procedures in brown bear is the basis for establishing a specific genetic resource bank aimed at the preservation of a Cantabric brown bear population, which is seriously threatened. Several issues complicate the development of these cryopreservation procedures: lack of previous specific studies, a high incidence of urospermia and spermagglutination observed in bear ejaculates. Moreover, the availability of individuals for research from these threatened populations is problematic. In the case of the Cantabric brown bear, we have used males from other populations, but of the same species, as surrogates, to carry out a direct extrapolation of the results. Urospermia-- Moreover, 70% of the ejaculates are urine contaminated and spermagglutination have a detrimental effect on post-thawing cell quality recovery in this species. Considering the high value of these samples (autochthonous population with few individuals), a pre-selection of the ejaculates is not a viable alternative. Preventive methods reducing the mentioned detrimental effects need to be developed. On the basis of previous data, we can suppose that bear spermatozoa resist freezing injuries well. Nevertheless, because of the scarcity of this information, it is necessary to conduct further research on bear semen freezing under field conditions. Epidydimal spermatozoa can be important for genetic resource banking of threatened populations and thus specific cryobiological protocols need to be assayed. To date, 168 brown bear ejaculates have been frozen by the ITRA-ULE group at the University of León (Spain) in the development of methodologies for the preservation of brown bear sperm.

Spermatozoa recovery and post-thawing quality of brown bear ejaculates is affected for centrifugation regimes

“…The present study must be situated in the context of the conservation of the endangered Cantabric brown bear (∼150 individuals restricted to two isolated populations in the north of Spain) and in the development of artificial reproduction techniques to establish germplasm banks to aid in preservation of these populations (Anel et al 2008).…”

Effects on brown bear (Ursus arctos) spermatozoa freezability of different extender and dilution ratios used for pre-freezing centrifugation

“…Different studies on electroejaculation of bears have indicated an elevated incidence of urospermia, with the consequent loss of semen quality (Okano et al 2004;Chen et al 2007;Kojima et al 2001;Anel et al 2008). Thus, we considered that developing a protocol for washing sperm samples was critical for the success of a sperm recovery plan in the brown bear.…”

“…Some species such as the bear (Kojima et al 2001;Chen et al 2007;Anel et al 2008) may yield semen contaminated by the urine during electroejaculation. A usual method for counteracting the noxious effect of urine contamination is to add large volumes of extender to the contaminated sample and centrifuge it immediately, removing the supernatant and substituting it with clean medium (Makler et al 1981;Kim and Kim 1998).…”

“…Genetic resource banks could help to reverse that situation, allowing the storage of gametes and embryos for long periods, eventually applying this material in recovery programmes using assisted reproduction techniques. Adapting artificial reproductive techniques to the brown bear should be a priority in the recovery plans for this population (Anel et al 2008).…”

Genome Banking for Vertebrates Wildlife Conservation

“…Even so, ejaculates often come with urine contamination (e.g. Anel et al, 2008) or they may come with or without the relevant secretions from all accessory glands. In elephants this is manifested by occasional ejaculates with very sticky consistency indicating that high level of secretions from the bulbourethral gland are present (personal observation) whereas in rhinoceros it is manifested by high viscosity of the ejaculate (Behr et al, 2009b).…”