Ejaculate‐hormonal traits in the leopard cat (Felis bengalensis) and sperm function as measured by in vitro penetration of zona‐free hamster ova and zona‐intact domestic cat oocytes

Abstract

Electroejaculate traits and circulating follicle-stimulating hormone (FSH), luteinizing hormone (LhH), and testosterone concentrations were analyzed in adult leopard cats {Fells bengalensis), a rare felid species indigenous to east Asia. The ability of leopard cat sperm to bind and penetrate zona-free hamster ova and zonaintact domestic cat oocytes in vitro was examined as a means of testing sperm function. The influence of culture media [Biggers, Whitten, Whittingham (BWW) vs. modified Krebs Ringer bicarbonate (mKRB)j, seminal plasma removal, and swim-up separation on sperm motility, sperm morphology, and oocyte penetration also were assessed. Sperm treatments included dilution of raw semen (DR), ejaculate centrifugation, and either resuspension (NS) or swim-up processing (SU). The percentage of oocytes penetrated (penetration rate) and the number of penetrated sperm/oocyte (penetration index) were determined. Ejaculates from each male consisted of at least a 50% sperm motility rating, and hormone concentrations in individual males were unrelated to any ejaculate trait measured concurrently on the same day. The SU technique improved (P < 0.05) percent sperm motility and the proportion of structurally normal sperm compared to DR and NS treatments. Leopard cat spermatozoa were capable of binding to and penetrating hamster ova and domestic cat oocytes; however, penetration was influenced by culture medium and seminal processing. In the hamster assay, a higher (P < 0.05) penetration rate and penetration index were achieved when mKRB was used for gamete incubation instead of BWW. NS processing also increased (P< 0.05) overall penetration compared to DR and SU. In the cat oocyte assay, zona penetration rate was similar (P > 0.05) in the DR, NS, and SU aliquots; however, the zona penetration index was increased (P < 0.05) by the NS compared to the DR and SU treatments. This study 1) provides baseline ejaculate and endocrine norms for the leopard cat, 2) demonstrates that leopard cat sperm undergo nuclear decondensation in hamster ova and penetrate zona-intact domestic cat oocytes, 3) indicates that seminal plasma removal enhances leopard cat sperm fertilizing ability and ovum penetration, and 4| suggests that heterologous oocyte penetration is effective for assessing factors influencing fertilization and sperm function in this nondomestic felid.

Seasonal changes in activity of males’ reproductive system in Eurasian lynx

“…We did not find such correlation in Eurasian lynx, but the lowest sperm concentration was described for the mating period when the percentage of morphologically intact sperms was at the maximum. Sperm concentration in Eurasian lynx was comparable with concentrations known for other cat species (Far-East wildcat Prionailurus bengalensis euptilurus -73 mln/ml; cheetah -22 mln/ml; Bengal cat Prionailurus bengalensis -37 mln/ml; tomcats -108 mln/ml) (Howard & Wildt, 1990;Crosier et al, 2007;Pavlova, 2010;Glukhov, Naidenko, 2013). In Eurasian lynxes sperm concentration was estimated before 0-30 mln/ml, but highly increased with the decrease of ejaculate volume (up to 540 mln/ml) .…”

“…In tomcats high sperm concentration is usually related with the high percentage of morphologically abnormal sperms (more than 60%) (Howard & Wildt, 1990). We did not find such correlation in Eurasian lynx, but the lowest sperm concentration was described for the mating period when the percentage of morphologically intact sperms was at the maximum.…”

Function and culture requirements of snow leopard (Panthera uncia) spermatozoa in vitro

“…The cat zona pellucida is composed of a phenotypically distinct bilayer (Andrews et al, 1992). Snow leopard sper¬ matozoa readily bound and penetrated the outer layer of this zona pellucida, as do leopard cat (Howard and Wildt, 1990) and tiger (Donoghue et al, 1992c) spermatozoa co-cultured with domestic cat eggs. However, snow leopard spermatozoa could not penetrate the inner zona layer of these heterologous eggs.…”

Semen Characteristics of the Captive Indian Leopard, Panthera pardus

“…File # 02em morphologically abnormal spermatozoa in fertilization is debatable (Howard and Wildt, 1990). The ejaculated spermatozoa were cryopreserved using the test-yolk buffer supplemented with 8% glycerol (pH 7.4).…”