Species may be saved by microwaving sperm
Dehydration might offer a better alternative to freezing when it comes to tissue storage. Andrew Masterson reports.
Putting your cat in the microwave is universally agreed to be a very bad idea – but putting its sperm in there instead, it turns out, is potentially an excellent one.
The successful microwave drying of domestic cat sperm, described in a paper in the journal Theriogenology, could be the key to more resilient conservation practices for wild animal populations threatened by extinction.
In the paper, a small team led by Jennifer Patrick from the University of North Carolina in the US report using microwaves to gently dry out cat sperm immersed in a sugar called trehalose.
The dried sperm was later rehydrated and found to have sustained only minimal DNA damage. It turned out to be still viable, capable of producing embryos in a Petri dish.
Patrick and her team have previously reported success in dehydrating and reviving cat eggs. Being able to duplicate the process with sperm, they write, could point to new strategies for conserving endangered species – especially, in the first instance, wild felines.
As with plants and stored seeds, rare animal species could be future-proofed and protected from changing environmental and climatic conditions if their eggs and sperm were preserved in de facto libraries.
This is, of course, to an extent already done, but current methods involve freezing the sex cells. Preserving them is thus energy-intensive and, should power supply fail, liable to catastrophic failure.
"When you are thinking about long-term preservation of organisms, you aren't concerned with just electrical interruptions. Flooding and other weather events can require the relocation of samples under duress," says co-author Gloria Elliott.
Drying, in contrast, offers a stable alternative that does not require externally induced low temperatures. Invertebrate species such as tardigrades and brine shrimps that often enter dried-out states of suspended animation, and survive thus for years, do so by accumulating high concentrations of sugars similar to trehalose.
Inside the cells, the sugars replace water lost during dehydration, producing a highly viscous, glass-like matrix that stops all chemical and enzyme activity.
The fact that the matrix remains stable at room temperature, and that once the drying is complete there is no need for specialised storage, is potentially a boon for species preservation strategies.
"Frozen samples aren't easily transportable whereas if your samples are stored as dry packets - just like dried fruits or any dry goods you have on a shelf - you can toss your collection in a bag and out the door you go,” says Elliot.
“That's the concept -- not only to keep the cost of storage low, but to make specimens easily transportable, facilitating the sharing or relocation of specimens."