To a female sand goby fish, this little guy could be everything she’s looking for. He has great dancing moves, good rhythm, and a fantastic burrow that looks like a fine place to leave some eggs. But before she commits to spawning, she’ll need to give his bachelor pad a sniff.
She’s not being a neat freak, she’s being a good mother. Female sand gobies mate with many males, leaving eggs in each burrow for the father to care for. But even though she’s spreading her eggs around, she invested a lot of energy in growing each one. It’s a bad idea to waste them. New research by ecologists at University of Turku and the University of Gothenburg, appearing this week in Biology Letters, suggests that she can use her sense of smell to tell whether a potential mate will take good care of them.
As male sand gobies attract females, they collect eggs in their burrows. The eggs need oxygen, which their father provides by fanning them with his fins. The fanning also removes wastes from around the eggs. But all that fanning also uses up energy that a male might otherwise use to attract new partners. If the male shirks his fatherly duties, he may get more females to enter his burrow — but then his developing eggs can become infected and die. Topi Lehtonen and Charlotta Kvarnemo wondered whether the condition of the eggs in a burrow could sway how females chose their mates.
They started by setting up an aquarium that gave females who were ready to mate a choice of two males. Their first tests simply identified which male the female liked better. The next experiment randomly selected one of the males and pumped water that had been exposed to infected eggs through his burrow.
Their results were startling: almost every female chose to mate with the “cleaner” male, even if she had preferred the other male before. As far as Lehtonen and Kvarnemo could tell, both males still tried their best to get the female to commit, and got her to inspect both burrows each time. But even when the males looked great and sounded great, the smell of a ‘dirty’ nest sent her packing.
Read the full paper at Biology Letters.
Image: Topi Lehtonen, used with permission.