Scientists from the University of Guelph in Canada have found that the cannablistic mangrove killifish will never eat their own embryos. Yes, that’s right, even if they’re hungry. Phew!
Of course, the piscivorous fish will still consume the offspring of other parents, but a fish has to eat, right? The study is published in the journal Behaviour Ecology and Sociobiology.
"To our knowledge, this is the first time that the ability to recognize the genetic relatedness of a single embryo by a fish has been described in the literature," said Patricia Wright in a statement.
Previous studies have shown that the mangrove killifish, also known as the mangrove rivulvus, can survive on land for over 60 days. This is because the fish can live pretty much anywhere it likes – okay, so maybe not anywhere, but the fish are able to manipulate their gills to live out of water. They often live in logs, and when the water comes back, they convert their gills back to water life.
Along with its amphibious traits, the mangrove killifish is also a rare example of a vertebrate hermaphrodite that can naturally fertilize itself. This means offspring are genetically identical to their parent. The fish's incredible abilities were one of the reasons why the researchers decided to conduct this experiment in the first place.
For the study, Wells and Wright added an embryo into the water, which included an adult-sized fish it wasn’t related to. Each time they did, the fish reacted with speed and ate it. However, when an embryo that was related to the mangrove killifish was put in, the adult's behavior changed and it approached at a much slower pace.
"This suggests that they have the ability to recognize solo relatives at very early stages of development," said Michael Wells. The researchers suggest that waterborne odors or chemical cues may be involved in the ability of the fish to recognize kin.
The team included fish that had fasted as well as those that were fed. When the embryos were put in with the killifish, those that were unfed were “seven times faster” at approaching the embryo than the fish that were fed. Their curiosity may have made them speed up, but what didn’t change was the parent's refusal to eat its own embryo.