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The cuckoo catfish is a bad paying parent, leaving his little ones to others.
Roberto Nistri / Alamy Stock Photo
By Elizabeth Pennisi
Like the cuckoo with which he shares a name, the cuckoo catfish avoids his parental duties. The East African lake swimmer abandons his eggs to the care of other species. The researchers have now learned how he succeeds in this trick and how his offspring intervenes in the action.
More than 90 bird species, including cuckoos, are "brood parasites". They do not build their own nests; instead, they rely on other birds to take care of their young ones. But the cuckoo catfish (Synodontis multipunctatus) seems to be the only other vertebrate to adopt this strategy. In Lake Tanganyika, East Africa, catfish has a very special purpose: the thick-lipped cichlid fish that feeds on the mouth to rear its young. When the cichlid lays its own eggs, which it then stuffs into the mouth, pairs of wild catfish sneak into it to fertilize and fertilize their own eggs at the same spot. In the created chaos, the cichlidea picks up its eggs and theirs.
Last year, researchers showed that some mothers of cichlids were smart enough to avoid picking up catfish eggs. Now these same researchers – with a second team – showed how the catfish reacted. In their laboratory at the University of Colorado at Boulder, Marcus Cohen, an ecologist of evolution, compared the development of catfish and cichlid eggs. Catfish eggs grew faster, earlier and were larger than cichlid eggs laid at the same time, giving the catfish an evolutionary advantage, Cohen's team said. next month in the Philosophical Transactions of the Royal Society B.
These differences are bad news for young cichlids, which begin to hatch at about the same time that catfish embryos have to start feeding. Catfish intruders use their wide jaws and extra teeth to devour new head-first hatching. If the catfish lacks cichlid hatchlings, they begin to enchant them.
Meanwhile, another team discovered that larger eggs and faster development provided a second benefit to the young catfish. Martin Reichard, a biologist at the Institute of Vertebrate Biology at the Brno Academy of Sciences in Brno, and his colleagues found that catfish eggs that were rejected or missed by the cichlid parent ended up hatching and developing very slowly. well outside the mouth of the cichlid. But when the cichlid mommy lets it smolder while she feeds, the young catfish can jump inside when she picks up her fries, reports the Reichard team in the same issue of the newspaper.
This ability to invade fish in two stages distinguishes them from parasitic birds, says Sheena Cotter, an evolutionary ecologist at the University of Lincoln in the UK, who did not participate in the work. "It certainly does not happen in birds."
This ability of catfish to survive on their own also suggests that catfish – unlike cuckoo – has not yet fully developed a reliance on cichlids to rear their young, write Reichard and his colleagues. The tendency of cichlids to consume young catfish may even have contributed to the evolution of this dependence, he added.
These articles should encourage researchers to look for more examples of brood parasitism, Cotter says. "It's entirely possible that this will happen in other systems."
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