Superior sperm: investigating protocols to enhance anuran sperm quality

Captive breeding programs (CBPs) are essential for providing insurance populations of threatened amphibians, yet often face inherent difficulties associated with stimulating breeding behaviour in captivity. In recent years, the emerging field of amphibian assisted reproductive technologies (ARTs) has gained momentum as a solution to the low propagation of viable offspring. ARTs aim to enhance fertility through the manipulation of male and female gametes, and may include techniques such as the hormonal induction of gamete-release, artificial fertilisation (AF) and short-term (refrigerated) and long-term (cryopreservation) gamete storage. Sperm quality is arguably one of the most important factors leading to successful AF in vertebrates, however, knowledge of the factors influencing sperm quality among anuran amphibians remains limited. Chilled-sperm storage (between 0 and 10°C) is integral to successful AF in frogs because asynchrony of gamete release is common and sperm can be stored short-term while oocytes are collected. Poor sperm recovery post-storage has been reported across various species and suboptimal storage and activation conditions appear to be the primary cause. However, we currently know very little about what conditions are optimal to support sperm during storage, and for their successful motility activation post- storage. Additionally, to obtain optimal sperm quality required for AF, there might be value in manipulating certain aspects of the captive environment. Diet and nutrition have been strongly linked to sperm quality and performance across vertebrate groups, however, little is known about the effect of specific nutrients and minerals on male reproductive performance in anurans. To date, very few studies have attempted to manipulate the diet of captive anurans as a means to improve the reproductive condition of individuals, and in turn, reproductive outcomes