Terrapins: At Well Past 100, They're in the Mood

[Patti Kane-Vanni <pkv1@erols.com>]

Though not quite dinosaurian, the mighty turtle manages to outdo the dinos 
and the humans!  Check out this article in The Philadelphia Inquirer.  It 
spotlights colleague Jim Spotila and his terrapin research, and mentions 
fellow paleontologist Peter Dodson. Nice extinction theory too.

Terrapins: At Well Past 100, They're in the Mood.
It sounded incredible. A species that can live virtually forever, enjoy sex 
well into its second century, and bypass menopause completely.
The full article will be available on the Web for a limited time:
http://www.philly.com/mld/philly/living/columnists/faye_flam/15321719.htm
(c) 2006 Philadelphia Inquirer and wire service sources. All Rights 
Reserved.

   - Patti
(And just in case you can't get to it...)

Terrapins: At well past 100, they're in the mood
By Faye Flam

It sounded incredible. A species that can live virtually forever, enjoy sex 
well into its second century, and bypass menopause completely.
Rumor had it such a charmed life belonged to a humble turtle that inhabited 
the marshlands of the Jersey Shore.
To get the scoop on the secret lives of turtles, I went to visit 
international turtle expert James Spotila of Drexel University. It just 
happens that Spotila was taking time off from following the 
fast-disappearing sea turtles to catalogue a closer-to-home species - the 
marsh-dwelling diamondback terrapin.
I found Spotila near Waretown, N.J., at a rare undeveloped stretch along 
Barnegat Bay. Cormorants waded and the afternoon sea breeze rustled through 
the scrubby trees. The area had been set aside as a camp for the blind from 
the 1920s to the 1990s; environmental activists managed to save it as a 
research station.
Spotila doesn't know if the terrapins are endangered. "No one has counted 
them," he says. Their habitat is getting squeezed by condos, and hundreds 
get crushed under the tires of careless drivers. So this year he and his 
graduate students are tagging the population here.
In a wooden shack converted into a laboratory, a tank held some diamondback 
terrapins, the big ones about the size of dinner plates. Interlocking 
pyramids that rose from their backs displayed the concentric rings that 
reveal a turtle's age.
Palm-sized turtles that I assumed were babies flapped around as if plotting 
escape. "Those aren't babies," said Spotila. "They're males." The females 
benefit from being big because they can lay more eggs, he says. A clutch can 
have from 3 to 18 depending on the mother's size. "Males just have to be big 
enough to jump on the back of the females."
What made them male or female? He says these turtles remain in sexual limbo 
until about two-thirds of the way to hatching time. After that, they become 
male if they're cooler than about 84 degrees, female if they're warmer.
Scientists still don't know how it all works, though some suspect heat 
changes the activity of an enzyme called aromatase, which converts 
testosterone to estrogen.
Wouldn't you get a skewed sex ratio every time you had a hot or a cold year, 
I asked. Spotila said it averages out in the long run, and newly mature 
turtles can always mate with turtles many generations older.
That's because turtles don't age the way people do, says Spotila. It's hard 
to comprehend this, since we humans are programmed to grow old and die, but 
turtles don't senesce and don't die until they get diseased or killed by 
predator, car or fishing net.
They don't go through menopause or lose their sex appeal but instead 
continue to mate and reproduce every year until they die - which for some 
can go on well over a century. So there's no problem for a 105-year-old 
female to make babies with a 5-year-old male.
And if a warm spell leads to a male shortage, females can use sperm stored 
away from trysts as far back as five years, says Spotila. "They're lucky - 
they don't have to deal with the males," he says. Or at least not every 
year.
Spotila said there's still much mystery in turtle sex. Scientists don't know 
whether females mate with many males in a season, whether they're picky 
about mating, or when they use the leftover sperm.
But there are hazards to letting the weather determine your sex.
A few years ago Spotila and Penn Veterinary School paleontologist Peter 
Dodson wrote a paper suggesting that temperature may have determined the sex 
of dinosaurs.
When a catastrophic event altered the climate 65 million years ago, turtles 
managed to adjust, perhaps evolving a lower female-producing temperature, 
while dinosaurs could have gone years without hatching females. If that was 
the case, Spotila says, "the last dinosaur was a frustrated male."

Contact staff writer Faye Flam at 215-854-4977 or fflam@phillynews.com

Patti Kane-Vanni
Bala Cynwyd, PA  19004, USA
pkv1@erols.com or paleopatti@hotmail.com
http://groups.msn.com/DinosaurandFossilDigs
"Keep away from people who try to belittle your ambitions.  Small people 
always do that, but really great ones make you feel that you too, can become 
great." - Mark Twain