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Date Posted: 05:53:56 09/21/02 Sat
Author: Weird_Enigma
Author Host/IP: 209.252.119.3
Subject: virgin birth by a lone shark

Apparent `virgin birth' is a shark-tank shocker
Aquarium oddity is only 2nd such U.S. case
DAN SHINE
Knight Ridder

DETROIT - A female whitespotted bamboo shark at the Belle Isle Aquarium has given birth to three babies even though she has not been near a male shark in at least six years.

Often called a "virgin birth," it is only the second such known occurrence at an accredited U.S. zoo or aquarium.

"Fish do so many quirky things," said Doug Sweet, curator of fishes at the Detroit aquarium.

Female sharks, like many animals, will lay infertile eggs even if there is no male mate around.

Normally, it's assumed the eggs are not viable and are thrown out.

But when the bamboo shark laid eggs in late winter, Sweet left them in the tank because he had heard about a bonnethead shark at a Nebraska zoo that had a virgin birth last year.

The first bamboo shark egg hatched in July. It was followed soon by another, and a third egg hatched this week.

Genetic testing will be done to see if the births can be explained, but Sweet said not everything about sharks' DNA is known.

It is possible the Detroit shark, which is about 2 feet long, was impregnated before she arrived at the aquarium and retained sperm in her reproductive tract. But Sweet said that is highly unlikely because the female probably never came in contact with a male and doesn't typically breed at the size she was when she came to Belle Isle.

The mother could have both male and female reproductive characteristics and be able to self-fertilize its eggs.

The most likely scenario -- though thought to be very rare -- is the shark stimulated the eggs without sperm. This process, known as parthenogenesis, is the ability of unfertilized eggs to develop into embryos without sperm. It is common in snails and water fleas but becomes more unusual in higher vertebrates.

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