Post-natal sexual development of testis and epididymis in the rabbit: variability and relationships among macroscopic and microscopic markers.

The present work was performed to examine the existence of some relationships between macroscopic and microscopic traits of testis and epididymis in rabbit. The variables studied were live weight (LW), testis length (TL), testis width (TWh), testis weight (TW), testis volume (TV), epididymis length (EL), epididymis width (EWh), epididymis weight (EW), epididymis volume (EV), percentage of seminiferous tubules with presence of lumen (STL), percentage of seminiferous tubules with presence of elongated spermatids (STES), percentage of seminiferous tubules with presence of spermatozoa (STS) and diameter of seminiferous tubules (STD). Measurements began after weaning and continued until males reached 33 weeks of age. Phenotypic correlations between testis and epidydimis traits and the principal component analysis were estimated as the residual correlation from an analysis of variance, including the effects of line, birth-season, age, and the double interactions line x age and birth-season x age. Four principal components (PCs) explained 79% of the total variation. The predominant variables defining the first PC were TL, TW and TV. Epididymis width and STS were located in the second PC. Epididymis weight and EV were important in the definition of the first and third PC. Tubular diameter seems important in the definition of the fourth PC. It has been not found correlation between traits related to either testis or epididymis size and variables related to active spermatogenesis. Therefore, TW and/or TV seemed not to be good markers of maturity.