Morphology, morphometry, and membrane integrity of epididymal spermatozoa of spotted pacas (Cuniculus paca, Linnaeus 1766)

The objective of this study was to evaluate the morphology, morphometry, and membrane integrity of epididymal spermatozoa of spotted pacas using spermatic cells collected from the epididymal tails of five animals. The flotation method using the ACP-123 (R) and Botusemen Special (R) extenders was performed, and samples were stained in Diff-Quick and eosin-nigrosine. Descriptive statistics of data were obtained and Student's t-test was performed. The morphology of 200 Diff-Quick-stained spermatozoa showed that they had an oval head with three vesicles in the acrosomal region, a midpiece, an elongated tail; moreover, 27% of the spermatozoa exhibited cellular defects. The morphometry of 100 sperm cells (analyzed with an optical microscope and the EZ Leica LAS software for Windows) presented the following measurements (mean +/- SD): total length 43.87 +/- 4.91 mu m, head 7.54 +/- 0.82 mu m, midpiece 5.35 +/- 0.83 mu m, tail 30.72 +/- 2.55 mu m, and head width 5.30 +/- 0.68 mu m. Of the 2,000 cells stained with eosin-nigrosine for membrane integrity evaluation, 83.8% diluted in ACP-123 (R) and 72.9% diluted in Botusemen (R) had intact membranes. The results of this study suggest that epididymal spermatozoa of pacas can be used in assisted reproduction programs; moreover, our study adds knowledge to the reproductive biology of wild animals, and encourages further research on the role of the three acrosomal vesicles present in this species.