Equine sperm nuclei with different ploidy levels: relationship between the nuclear DNA content and the nuclear area

Abstract

The aims of this study were to estimate the ability of the Feulgen reaction to identify equine sperm nuclei with different ploidy levels, to determine the frequency of haploid, diploid and polyploid sperm nuclei in the semen of fertile equines and to evaluate the relationship between the nuclear DNA content and the nuclear area. Determination of the ploidy level of Feulgen-stained spermatozoa using a scanning microspectrophotometer was very similar to the subjective estimations made with a light microscope. This indicates that the Feulgen reaction is a simple, inexpensive and reliable technique to recognise the ploidy level of equine spermatozoa. The incidence of diploid and polyploid spermatozoa, determined with a light microscope in 11 fertile equines, was 0.17 ± 0.08% and 0.027 ± 0.027% respectively. DNA content values obtained by microspectrophotometry in the only equine that presented polyploid spermatozoa allowed us to discriminate between haploid, diploid and polyploid subpopulations. Measurement of the nuclear area discriminated only two subpopulations: one including the haploid and diploid subpopulations and the other including the polyploid one. The similarity between the area of the haploid and diploid sperm nuclei suggests that the increase in DNA content is anisotropic, with a privileged direction of growth perpendicular to the nuclear flattening plane.

Morphology, morphometry and chromatin distribution in llama sperm nuclei

“…The similarity in the nuclear areas and the differences in the values of MaxAbs and MeanAbs suggest that the increase in DNA in diploid spermatozoa is anisotropic, with a privileged direction of growth, that is the Z-axis (Figure 3d), which is perpendicular to the flattening plane of the sperm. Similar observations have been made in bovine spermatozoa (Ferrari, Spirito, Giuliano, Campi, & Fernández, 2006) and equine spermatozoa (Spirito et al, 2011).…”

“…These nuclei had a size similar to that of haploid nuclei but a notorious darker colour and a broader post‐acrosomal zone, and were observed in a very low frequency (0.55%). Diploid nuclei have been found in different mammalian species (Ferrari et al., ; Spirito et al., ; Vieytes et al., ), and although their frequency is usually low in normal semen, they may cause spontaneous abortion and contribute to the production of triploid embryos (Rosenbusch, ). The similarity in the nuclear areas and the differences in the values of MaxAbs and MeanAbs suggest that the increase in DNA in diploid spermatozoa is anisotropic, with a privileged direction of growth, that is the Z‐axis (Figure d), which is perpendicular to the flattening plane of the sperm.…”

“…The haploid DNA content (C-DNA) per sperm nucleus expressed in picograms was calculated using G. domesticus erythrocytes as a standard (C-value = 1.25 pg, Gregory, 2016) and according to Spirito, Campi, Boquet, Fernández, andFerrari (2011) andFerrari et al (2012).…”