Male fish that keep eggs fertilized by other males in their mouths. This was noted by a team of researchers from Charles Darwin University in Australia. They were interested in two types of freshwater “brood fish”, Glossamia area And Neoarius graeffei. The team sequenced different genes from the incubating males and their fry. Their “funny” results were published in the journal Biology Letters.
Why do these male fish spawn eggs?
The team that led the study explains the males’ interest in incubating eggs in their mouths. Basically, it seems too disruptive to them. The presence of eggs in their mouths prevents them from eating, if not completely.
Although this nursery is quite an effort for them, it can be beneficial for them. In fact, according to Janine Apssia, a postdoctoral researcher and lead author of the study, “it appears to be a way for males to impress females.”
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The eggs of these fish can be hatched by several different males.
The researchers genetically sequenced the “brooding males” and the larvae they were holding in their mouths. Target? Find out if the fry were incubated by their father and whether they were from multiple fathers.
at Neoarius graeffei All the fry came from monogamous parents and the incubating male is the father. But it was different with Glossamia area. We can distinguish 4 types of configurations.
In the first, all fry came from monogamous parents and the incubating male was the father (73.3% of cases). In the second, some larvae came from the same brood from two different mothers and one brooding father (13.3% of cases). In another formation, the fry were not genetically related to the incubated male (6.67% of cases). Or in the latter, the fry came from two different parents and a single mother (6.67% of cases).
Cannibalism, hunting… Possible explanations were given by observations.
Researchers have repeatedly observed a case in which a female incubated eggs chased after a male. Which forced him to refuse them. Eggs that did not return after that. This may be an opportunity for males who do not have eggs to hatch, to recover some. But also for other males, they have more. This would explain that some of the larvae were not genetically related.
Regarding eggs from two different nations. This can happen if some of the eggs from the first female have been partially eaten. Yes eaten! By practicing cannibalism, the male leaves room for new eggs.
Although the families of fish that practice oral sterilization are known, this phenomenon is still little studied. Scientists do not yet understand the evolutionary value of this parenting strategy.
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