Species of shark turns cannibalistic while still in the womb

May 1, 2013 at 3:33 PM   |   Comments

STONY BROOK, N.Y., May 1 (UPI) -- Sand tiger sharks compete with each other while still in the mother's womb, turning to cannibalism until only one survives to be born, U.S. researchers say.

Marine biology professor Demian Chapman of Stony Brook University in New York said when a female shark gets pregnant, it's usually with multiple offspring of several different male sharks, but as soon as the fetuses are old enough, they begin a cannibalistic battle for survival.

Scientists say they believe it's not a response to crowded conditions within the womb but represents an evolutionary strategy wherein the most aggressive male sharks father the ultimately successful baby and thereby out-compete rivals, The Washington Post reported Wednesday.

"For most species, we think of sexual selection as ending when males fertilize eggs, because once the male's fertilized eggs he's won, [and] there will be some genetic representation in the next generation," Chapman, lead author of the study published in Biology Letters, said. "This is demonstrating that embryonic cannibalism is actually whittling down the number of males producing offspring."

Female sand tiger sharks have two uteri and can mate with many male sand tiger sharks, but after a 12-month pregnancy they produce just two offspring, one from each uterus.

Like many other shark mothers, female sand tigers abandon their young after giving birth, and given the proven aggressive tendencies of their offspring the mothers "probably run a mile," Chapman said.

© 2013 United Press International, Inc. All Rights Reserved. Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.
Recommended UPI Stories
Featured UPI Collection
Notable deaths of 2014 [PHOTOS]

Notable deaths of 2014 [PHOTOS]

Most Popular
Mars rover spots rock shaped like thigh bone
Parched land in the drought-riddled West is actually rising
Tech industry All Stars developing 'Star Trek'-style communication badges
Latvia boasts world's first net for migrating bats
Neanderthals and humans interacted for thousands of years
Trending News