Take sea horses, for example, says Richard Grosberg, an evolutionary biologist at the University of California, Davis. "Male sea horses take care of the offspring. Male water bugs also carry eggs and babies on their back. There are toads that do the same thing as well."
But Grosberg says in the case of these sea horses and water bugs and toads, the offspring males are caring for are their own. Grosberg began to wonder if the same was true about these snails. It's not an unreasonable question; it's quite a Bacchanalian scene on the beach at mating time.
"There are thousands and thousands of males and female snails, all mixing and changing partners presumably, so we wondered whether or not the males that were caring for the babies were actually the fathers of the babies that they were caring for," he says.
So Grosberg and his colleague Stephanie Kamel brought the males back to the lab and did paternity tests on those itty bitty snails the males were schlepping around. And lo and behold: "We found that in fact, very few of the offspring that the male was carrying around were his," Kamel says.
In other words, says Kamel, not only was the male snail doing all the heavy lifting — and becoming an easy target for birds with a bunch of bright white eggs on his shell — "he was taking care of babies from, basically, 25 other guys."