Magazine article Science News

Bluegill Dads: Not Mine? Why Bother? (Fishy Paternity Defense)

Magazine article Science News

Bluegill Dads: Not Mine? Why Bother? (Fishy Paternity Defense)

Article excerpt

Bluegill sunfish have provided an unusually tidy test of the much-discussed prediction that animal dads' diligence in child care depends on how certain they are that the offspring really are their own.

When researchers presented male bluegills with phony evidence of cuckoldry, the dads slacked off on nest defense, says Bryan Neff of the University of Western Ontario in London, Canada. Later, reassured of their paternity, the fish grew fiercely protective, Neff reports in the April 17 Nature.

The idea that genetic relatedness affects how liberally parents invest in their offspring makes sense theoretically, but it's been tricky to test, says David Westneat of the University of Kentucky in Lexington, who also studies parental care. However, he calls the new study"a really focused, strong experiment" and "the best evidence to date"

The bluegill (Lepomis macrochirus) occurs across much of North America. In the Ontario lake that Neff studies, most males take 7 years to mature. Then, 100 to 200 hefty nest-builders gather, swishing their tails so that each sweeps out a depression, virtually rim-to-rim with his neighbors'. Schools of females show up for a day of egg laying. The dads fertilize the eggs, and the females swim off. The male spends the next week guarding his 12,000 to 60,000 offspring without any break for foraging.

About 20 percent of males mature when only 2 years old and spend their lives siring offspring in other males' nests. When small, these cuckolders hide nearby and zoom in at a strategic moment to fertilize eggs. …

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