Sand fleas may actually benefit from global climate change.

Sand fleas and mole crabs. Photo: Shutterstock

Climate change is going to have a very strong impact on the world, and especially on the oceans. Rising temperatures and acidification, the latter caused by the ocean sequestering more carbon dioxide than normal, is already having a negative impact on corals and other ocean life. However, at least one species will likely benefit from global climate change.

Cymadusa pemptos, also known as sand fleas, will likely see a population boom. In lab experiments, the crustaceans were subjected to waters with temperatures and CO2 content projected for a century in the future. The females are typically attracted to males with the largest claws, but as the conditions changed, all males developed equally large claws. This meant that more of them were able to attract mates. They were also bigger in general.

More than 80 percent of the females became pregnant during breeding cycles, which is higher than normal. The result was a population explosion, which isn’t always good in and of itself, but in this case it was coupled with increased growth of the marine algae that the sand fleas, and other species, eat.

It looks like more sand flea males will be attracting mates in the future, though that is subject to change with evolution. Currently, females choose males with larger claws because they are better able to defend themselves and fight off other males. As claw size among male sand fleas becomes normalized, females will likely find some other way to distinguish which males are worth mating with.

Selection because of secondary sex characteristics is quite common in animals, and it seems unlikely that this attribute of their mating cycle would totally drop off in these creatures.

In the face of global climate change, it seems that sand fleas have a bright future. On the other hand, increasing sand flea and marine algae populations will impact the rest of the life which shares those ecosystems.

“We know that climate change will be cataclysmic for many species, but in some cases it will not,” says evolutionary biologist Dr. Pablo Munguia, one of the authors of the study. “This is the first quantitative example of how it will be beneficial for some individual species, albeit with massive consequences to the environment overall.”