Abstract

Bats, the second largest mammalian order, are widely distributed and of crucial importance for numerous ecosystems. The IUCN Red List of Threatened Species currently lists 77 bat species as Endangered or Critically Endangered.

Bat reproductive biology is highly diverse, comprising species capable of long-term sperm storage and delayed fertilization, delayed implantation, or delayed fetal development. Knowledge of these mechanisms is limited, and the use of assisted reproductive technologies (ARTs) has been rarely reported in the literature. As many bat species reproduce poorly in captivity, ART may become crucial to the conservation of endangered species.

For the first time we describe successful cryopreservation of bat sperm using a species that reproduces well in captivity, Carollia perspicillata, at Papiliorama, Kerzers, Switzerland. Epididymal preparations of 28 males were distributed evenly to compare four different sperm extenders using 7 independent sample sets. Initial progressive sperm motility ranged from 26.7% to 72.0% between extenders. Mean sperm concentration was 43.7x10⁶/ml. Sperm samples were loaded in straws and frozen over liquid nitrogen. Post-thaw motility in the four extenders Canifreeze, modified Canifreeze, Test egg yolk, and BotuCrio® averaged 14.7±4.0%, 34.2±4.5%, 45.3±4.1%, 33.6±4.5%, respectively. The best results were achieved using Test egg yolk extender, although no statistically significant difference was detected compared to modified Canifreeze or BotuCrio.

Developing sperm cryopreservation protocols for the various bat species facing the risk of extinction, particularly for semen obtained by manual massage or electroejaculation, and implementing artificial insemination protocols will be of high value for their successful future conservation.