In a paper published in Conservation Physiology, Simon Cllowlow and his colleagues at Macquarie University reveal a new sperm freezing and recovery technique that shows great promise in species recovery and includes an amazing ingredient.

The group took sperm from a series of yellow-spotted monitors – a giant lizard, or species of goanna, which in recent years has been severely affected by cane toad populations in their habitat. The lizard population needs urgent help, as it has already been destroyed by 97%, and this situation has a huge impact on the entire ecosystem.

The researchers decided to find out which method of freezing endangered semen samples works best. Scientists also wanted to develop a better protocol for resuming the movement of frozen sperm after thawing. They found that one common cryoprotectant worked quite well. Scientists have managed to prevent semen from breaking with ice crystals during the freezing process. But, as in the case of a small number of previous attempts to freeze reptile sperm, the researchers were not able to obtain a large number of motile, floating sperm after the thaw.

The research team decided to try a technique that had not previously been used with lizard specimens. This method previously increased the sperm movement of mammals and birds but was never applied to reptile sperm after freezing. Scientists added caffeine to stimulate sperm when thawed.

Researchers immediately saw a huge increase in the number of moving sperm cells after freezing and thawing.
It turns out that frozen lizard sperm need their morning coffee to start, like us!

Lachlan Campbell, student and first author of the research

After a series of experiments to improve the protocol, the team found that they were able to extract almost half of the frozen sperm, which ensured the largest recovery of motile sperm among all reptile species.

This method will help preserve reptiles around the world, which is especially important for Australian lizards. It provides new opportunities for creating the Kimberly Arc Gene Bank, an ambitious nature conservation project created by Cllowlow and his colleague Dr. Sean Doody at the University of South Florida. The project aims to restore genetic diversity after the sadly inevitable devastation of wildlife caused by an increase in the population of reed toads in western Northern Australia.