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It’s no secret that our planet is losing species to extinction every year. To save other animals from extinction, researchers are putting the sperm of a dolphin together with the egg of a cow and other hybrid experiments to figure out how to preserve the endangered animals’ sperm so they stay viable as long as possible. They are testing how well sperm fertilize all kinds of eggs after thawing, and some of those tests result in dolphin-cow hybrids.
To allow entry, some researchers have to take the outer coating of the egg off, called the zona pellucida, before their hybrid experiments could begin. But even bouncers aren’t perfect, and neither is the zona pellucida. For some hybrid experiments, researchers found that it allowed sperm from a different species right in. Researchers think that could happen because the two species are related just closely enough to get a pass, even if they’re pretty distant relatives. So knowing how sperm get past the zona pellucida is one of the first hurdles when it comes to making endangered animals in vitro. A group of researchers described their 2015 publication in which they successfully made dolphin-cow hybrids without altering the zona pellucida on any of the eggs. They wanted to understand if this could happen and how dolphin sperm would fertilize cow eggs. Surprisingly, dolphin sperm were more successful at attaching to cow eggs than bull sperm, even though that is the only job bull sperm have. However, the dolphin sperm didn’t produce as many viable offspring, which shows that fertilization is about more than just a sperm reaching an egg.
The experiment yielded hybrid embryos, proving that it is possible for dolphin sperm to fertilize cow eggs, though not as likely as bull sperm. The researchers then took it a step further to see if even more distantly related animals like dolphins and mice could hybridize. These combinations also made successful hybrids, though less frequently than the dolphin-cow hybrids. This might have been due to the mismatched internal structures and too many centrosomes.
The experiment showed that dolphin sperm are hearty and resilient, which bodes well for future IVF plans. This also demonstrates that when wanting to save endangered species, one needs to break a few eggs.
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