Identification of sperm head subpopulations with defined pleiomorphic characteristics in ejaculates of captive Goeldiʹs monkeys (Callimico goeldii)

The aim of this study was to evaluate the incidence of pleiomorphisms and its influence on the distribution of sperm morphometric subpopulations in ejaculates from the vulnerable Goeldiʹs monkey (Callimico goeldii) by using a combination of computerized analysis system and Principal Component Analysis (PCA) methods. Each sperm head was measured for four primary spermatozoal head dimensional parameters (area [A (μm2)], perimeter [P (μm)], length [L (μm)] and width [W (μm)]) and three head shape derived parameters (ellipticity [(L/W)], elongation [(L − W)/(L + W)] and rugosity [(4πA/P2)]). Six separate subpopulations (SPs) were identified: SP1, constituted by very large, narrow and very elliptical spermatozoa (A = 16.85 ± 1.56 μm2, W = 2.75 ± 0.42 μm and ellipticity = 2.16 ± 0.24); SP2, characterized by average sized, short, wide and round spermatozoa (A = 15.00 ± 1.92 μm2, L = 5.06 ± 0.49 μm, W = 3.51 ± 0.31 μm and ellipticity = 1.44 ± 0.15); SP3, represented by small, wide and slightly round spermatozoa (A = 14.95 ± 1.75 μm2, W = 3.47 ± 0.29 μm and ellipticity = 1.48 ± 0.14); SP4 included very small, short and very round spermatozoa (A = 14.15 ± 2.38 μm2, L = 4.90 ± 0.57 μm and elongation = 0.18 ± 0.05); SP5 consisted of average sized and slightly elliptical spermatozoa (A = 15.14 ± 1.72 μm2 and ellipticity = 1.49 ± 0.14); and SP6 included large and round spermatozoa (A = 16.30 ± 1.62 μm2 and elongation = 0.19 ± 0.04). There were differences in the sperm subpopulation distribution (P < 0.001) among the five donors analyzed. In conclusion, the results of the current study confirmed that the use of computer sperm analysis methods combined with PCA cluster analyses are useful methods to identify, classify, and characterize different sperm head morphometric subpopulations in neotropical primates. Broadening our knowledge of C. goeldii sperm morphometric abnormalities as well as developing reliable techniques for sperm evaluation may be essential for ex situ conservation of this threatened species.