|Abstract or Summary
- Background: Even with numerous successful Trap-Neuter-Release programs, feral cat populations continue to grow. Our laboratory is interested in determining if an underlying biological cause exists for the exuberant reproductive success in this once domestic subspecies. An earlier age for developing reproductive capacity (onset of spermatogenesis in males) may be one factor. For domestic toms, puberty is reported to occur around 8 months of age. Previous work by our laboratory has shown that normal morphologic sperm are present in vas deferens secretions of feral toms before 6 months of age. Therefore, our hypothesis was that in feral toms the onset of spermatogenesis occurred before 6 months of age. The study objective was to histologically evaluate testes from weanling (2 months of age) through adulthood (24 months of age) to determine when the onset of spermatogenesis occurs in feral toms.
Methods: Feral toms were presented for castration at a local Humane Society during August-October 2014. Age was determined by records provided from feral cat colony managers and confirmed with dental eruption patterns. The age groups were: 2-2.5 months (weanling; n=6), 3-4 months (juvenile; n=6), 5-6 months (pubertal; n=6), and 12-24 months (adult; n=6). General anesthesia was induced and a routine open castration was performed. Both testicles from each cat were hemi-sectioned, formalin-fixed, paraffin-embedded, cut into sections (6 µm), and stained with hematoxylin and eosin. The slides were evaluated by a single observer (EB) blinded to age group using bright field microscopy (200X). Evidence of spermatogenesis was determined on the basis of presence of spermatozoa in the seminiferous tubule lumen. In addition, perpendicular diameters measured from 5 tubules for each testis were averaged and mean ± SD was determined for each age group. Tubular diameter was compared using a Student’s t test where p < 0.05 was defined as significant. The presence of spermatozoa in the lumen was compared using a Chi-square test.
Results: Evidence of spermatogenesis in weanling, juvenile, pubertal, and adult toms was 0%, 17%, 67%, and 100%, respectively (p < 0.05 between successive age groups). The seminiferous tubular diameter was significantly larger in each successive age group (weanlings 88.10 ± 10.88 µm; juveniles 109.8 ± 8.89 µm; pubertal 142.2 ± 16.89 µm; adult 237.90 ± 52.45 µm).
Discussion: Juvenile feral toms in the current study had significantly wider tubular diameter than previously reported for domestic toms under 5 months of age (86 µm), which supports our hypothesis that spermatogenesis is occurring at an earlier age in ferals. However, the time of year the previous measurements in domestics was not reported. If these measurements were made outside of the breeding season, this may explain why the tubular diameters were smaller. Future studies are planned to determine if folliculogenesis occurs earlier in queens as well.