Issue, M. 2021. Vol.51 - 2 - 2019: Cover: Micrograph showing fluorescent merocyanine patterns on dog spermatozoa: opaque - low fluidity (spermatozoon on the left) or brilliant - high fluidity (spermatozoa on the right). Photograph captured by Alicia Alcantar-Rodríguez and provided by Ortega-Morales et al. Austral Journal of Veterinary Sciences. 51, 2 (Mar. 2021), 45–104.