Testicular biometry and semen characteristics in captive and wild squirrel monkey species (Saimiri sp.)

Differential phenotypic characteristics for taxonomic diagnosis purposes are well determined in the genus Saimiri (squirrel monkey). However, data on its reproductive characteristics are lacking. Our aim was to determine testicular biometry and correlate with seminal analysis in captive (Saimiri collinsi) and free living (Saimiri vanzolinii, Saimiri cassiquiarensis, and Saimiri macrodon) squirrel monkeys. Testicular length, width, height, circumference, and volume were measured. Testicular biometry showed no differences between right and left testicles within the same species, as well as among species. Semen collected by electroejaculation was constituted of a liquid and coagulated fraction, or only one of them. No significant difference was observed between mean volumes of liquid (49.2 ± 68.9 μL: S. collinsi; 28.3 ± 59.8 μL: S. vanzolinii; 5 ± 7.1 μL: S. cassiquiarensis; and 0 μL: S. macrodon) and coagulated (65.4 ± 142.1 μL: S. collinsi; 125.8 ± 142.5 μL: S. vanzolinii; 175 ± 176.8 μL: S. cassiquiarensis; and 500 μL: S. macrodon) fractions within species or when each fraction was compared among the studied species. No correlation between testicular volume and seminal volume was observed when liquid (R = 0.31, S. collinsi; R = -0.69, S. vanzolinii) and coagulated (R = 0.32, S. collinsi; R = -0.37, S. vanzolinii) fractions were evaluated. No sufficient data were obtained for the other two species. Seminal quality was similar among species, and the most common defect was coiled tail. The method of electroejaculation yielded satisfactory results on these species, under field conditions.