Elephants May Have Started out All Wet
Monastersky, R., Science News
A study of tiny elephant fetuses, one no bigger than a pea, suggests that the wrinkly skinned giants originally evolved as seagoing mammals that used their trunks as snorkels.
"For the first time, we now have a rational explanation for the unusual anatomical features of the elephant," says Ann P. Gaeth of the University of Melbourne in Parkville, Australia.
Some paleontologists, however, argue that this idea doesn't hold water.
The evidence comes from an investigation of seven fetal elephants found inside females that were shot to reduce overpopulation in a South African park. Gaeth and her colleagues studied the growth of kidneys and other organs in these specimens, the smallest of which had developed for only 58 days. Elephant gestation typically lasts 22 months.
The researchers were surprised to find dozens of small, funnel-shaped tubes, called nephrostomes, in the kidneys of the elephant fetuses. These features had not been seen in any mammal that gives birth to live young, the researchers report in the May 11 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES. Nephrostomes appear briefly in the embryos of egg-laying mammals, such as the platypus, and function in adult fish and amphibians.
The elephant's fetal nephrostomes are a legacy that provides clues about the animal's origins, say the researchers. Aquatic animals have nephrostomes, so elephants may 'have inherited this feature from an aquatic ancestor, says Gaeth. …