'Pregnant' fish fathers abort babies of ugly mums

Last Updated: Thu, Mar 18, 2010 07:40 hrs

A new research has found that pregnant male pipefish give birth to more young ones from attractive mates.

When it comes to mating, pipefish males always wait for bigger females to come along because 'pregnant' fathers kill off embryos conceived by an undesirable female to make room for the offspring of a potentially more attractive female.

Pipefish, sea horses, and sea dragons come from a family in which the males get pregnant. In some of these species, the females court and compete for males.

Lead author Kimberly Paczolt from Texas A and M University in College Station, said that the pair then do a dance, which includes "twitching at each other and spiralling together, like a double helix."

As they spiral around each other, the female transfers the eggs into two rows along its mate's body. The male then fertilizes the eggs, and the brood pouch - which consists of two flaps - glues itself together in the middle.

Weeks later, the seam breaks apart, tiny versions of the adults swim out, and the males are free to be impregnated again in as little as an hour.

The male's pouch protects the embryos and gives them oxygen and nutrients.

However, Paczolt said, the male doesn't care for the babies with utter abandon. Rather, he tempers how much he invests in the eggs according to how large the female is.

In the study, the researchers mated 22 male Gulf pipefish (Syngnathus scovelli) with two females each, in separate broods.

They found that the males preferred to mate with larger females, and that these more 'attractive' females transfer more eggs to the male and more of her young survive.

"Males are making trade-offs; when they have limited resources, they have to invest in the smartest ways possible," Nature quoted Paczolt as saying. (ANI)

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