Female fish assess potential partners with ‘test’ eggs

December 5th, 2009 - 5:08 pm ICT by ANI  

London, Dec 5 (ANI): Female scissortail sergeants gauge potential mates with a small batch of ‘test’ eggs before breeding with them, according to an ecologist.

Males may fail as fathers for a number of reasons-they may be unable to defend eggs when left in their care, for example, or even decide that the eggs would make a tasty snack.

Andrea Manica, of the University of Cambridge, UK, was studying the latter - behaviour called filial cannibalism - in scissortail sergeants (Abudefduf sexfasciatus) in Malaysia.

He then noticed that some females would approach a male’s nest, deposit a small number of eggs, then skedaddle.

Manica wondered whether the females were testing the males and thus he provided males with ceramic tiles to use as nest sites and patiently waited for females to lay small clutches of eggs on the tiles.

Then Manica - who spent up to six hours at a time underwater watching the fish - either left the tiles alone, or rotated them to move the eggs.

When the eggs were undisturbed, two-thirds of females who laid test eggs came back and laid a full clutch.

However, when the eggs were moved - implying that the father had been inattentive - only a quarter of females returned and laid a full clutch, ready for the male to fertilize.

Overall, only 7.4 percent of the roughly 421 females actually laid test eggs before breeding, and this strategy was used mainly at the start of the breeding cycle.

Later on, the number of eggs in a nest seemed to provide a reliable enough indicator that the father was up to the task.

“The female fish probably use these test eggs when they don’t have much to go by. As a strategy, to me it makes lots of sense. There are probably lots of other species that do that,” Nature quoted Manica as saying.

The study has been published in Animal Behaviour1. (ANI)

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