Electrostimulation is an effective and safe method for semen collection in medium-sized lizards

Abstract

The development of safe and consistent semen collection protocols should be ensured to understand basic sperm parameters of a species. Electroejaculation has been hypothesized and tested to be a safe method to evaluate male reproductive potential in wild animals. However, little is known about semen collection protocols in lizards. Adjusting stimulation to species and body mass is important for efficient semen collection as well as for animal welfare. Tropidurus spinulosus is a good model to adapt electrostimulation; it is a medium-sized lizard species, males have semen during a long period and operative sex ratio is male-biased. We aimed to provide a thorough and safe method for collecting semen samples from this animal model by means of electrostimulation and characterize basic sperm parameters. Mature males of T. spinulosus were captured and their testicular volume was evaluated via portable ultrasound scanning. The lizards were electrostimulated by performing standardized series of stimuli. Semen was obtained successfully in 94% of the males. Samples were contamination-free. Mean sperm number of ejaculates was 2.1 ± 1.8 × 106 spermatozoids. The percentage of motile spermatozoa was 78% and sperm dynamic parameters were: VSL 37.26 ± 7.72 μ/s and VCL 84.26 ± 16.27 μ/s. We observed high variability in testicular volume among males; however, almost all the individuals had sperm. Electrostimulation using protocols adjusted to a medium-sized lizard was an effective semen collection method that allowed us to obtain semen samples with high motility (percentage of motile spermatozoa and sperm velocity).