Sperm kinetics and motility subpopulation in XY and YY Nile tilapia (Oreochromis niloticus) males

Abstract

Incorporation of YY males into the commercial farming of Nile tilapia could generate populations composed of 100% males, but first, it is necessary to evaluate the quality parameters of the spermatozoa produced by a male with two Y chromosomes. The aim of the present study was to evaluate and compare the quality, kinetics and population structure of milt samples obtained from XY and YY Nile tilapia males. We used 60 males divided by sexual genotype into two groups, XY and YY. Milt volume, sperm concentration and several parameters of motility were measured by computer-assisted sperm analysis (CASA). Motility subpopulations were identified using a principal component analysis followed by a two-step cluster procedure. The values obtained for milt volume and sperm concentration showed significant differences (p < 0.05) with YY males showing the higher values. For motility parameters, linearity and straightness index showed significantly higher (p < 0.05) values for YY males while wobble index and mean amplitude of lateral head displacement were significantly higher (p < 0.05) for XY males. Four subpopulations were identified, two for each sexual genotype. Our results suggest that sperm quality of YY males is not negatively affected by the presence of two Y chromosomes.