Astatotilapia burtoni (A Burtoni) fish
Motherhood can be tiring and stressful that some mouthbrooding mothers snack on their young, according to a new study.
Raising young is physiologically demanding for the central African fish, called Astatotilapia burtoni (A Burtoni). While mouthbrooding, they can’t eat or breathe properly, writes National Geographic’s Tom Metcalfe.
The fish commonly called Burton’s mouthbrooder sometimes consumes more than three-quarters of their own eggs and baby fish.
A study published in Biology Letters not only reveals this cannibalism, but it suggests the mother fish that eat their own young reduce cell damage caused by mouthbrooding, writes James Ashworth for London’s Natural History Museum.
The study “adds an interesting piece to the puzzle of how these mouthbrooding females are able to survive and maintain their own health during the two-week brooding period when they can’t eat,” Karen Maruska, a biologist at Louisiana State University who studies A. burtoni but did not contribute to the new research, tells National Geographic.
Other animals eat their young too
A. burtoni aren’t the only fish that consume their progeny—a practice called “filial cannibalism.” Male barred-chin blenny and common goby fish munch on some of the eggs they’re supposed to be looking after. Guppies, too, eat their own babies. And some insects, birds, reptiles, amphibians and mammals have also been observed eating their offspring, per the Natural History Museum.
The researchers weren’t initially studying cannibalism—at first, they were interested in how mouthbrooding affects the health of female A. burtoni. In a 2019 study, Dijkstra and his colleagues found that the mothers’ bodies produced more chemicals that damage cells while mouthbrooding, New Scientist writes.
In the new study, the researchers looked at more than 60 female A. burtoni. Around half were mouthbrooding, and the other half were not, since the researchers removed their eggs, per New Scientist. After two weeks, 29 of the 31 mouthbrooders had fewer offspring—and their broods had become 40 percent smaller on average, according to National Geographic.
After two days, the mouthbrooders had 23.7 percent more DNA damage in their livers than the fish that were not raising young did. But after six days and again after two weeks, the brooders and non-brooders had similar levels of damage, per New Scientist. Sawecki tells the publication that the findings suggest eating their offspring reduces stress on the mothers’ bodies.
The researchers concluded that the missing offspring had been eaten. Doing so might have had health benefits for the mothers, the scientists suggest. Mouthbrooding fish had higher levels of chemicals called reactive oxygen species (ROS), which can damage DNA. The fish that had more of the harmful chemicals also ate more of their offspring. This could have provided them with antioxidants to counteract the imbalance of ROS.
The researchers hope that these experiments will demonstrate whether child eating is a symptom of stress in these fish, or the mothers' unusual way of dealing with it.
SOURCE
BIOLOGY LETTERS: “Mothers modify the cost of reproduction by dynamic changes in antioxidant function and filial cannibalism.”
NEW SCIENCE: “Reproduction and maternal care increase oxidative stress in a mouthbrooding cichlid fish.”
NATURAL HISTORY MUSEUM: “Some mouthbrooding fish eat their children to reduce stress.”