A new study exposed rats to common farm chemicals and found that the effect of the chemicals lasted multiple generations. (Photo by Tamara
A first-of-its-kind study supports the theory that some common agricultural chemicals can cause reproductive problems that are passed down through generations. The Great Lakes Radio Consortium’s Erin Toner reports:
A first-of-its-kind study shows some common agricultural chemicals can cause reproductive problems that are passed down through generations. The Great Lakes Radio Consortium’s Erin Toner reports:
In the study published in the journal Science, pregnant rats were exposed to high doses of two commonly-used chemicals: a fungicide used mainly by wine makers and a pesticide that replaced DDT.
The study showed the toxins caused low sperm counts in the rats’ male offspring down through four generations. Washington State University biologist Michael Skinner led the research team.
“This is a brand-new phenomenon; the fact that an environmental toxin can cause at all a multi-generational disease state, is something we didn’t know existed.”
Skinner stresses that the level of chemicals used in the study were above the level anticipated to be in the environment. But he says the research supports the idea that such toxins are causing permanent reproductive problems in men in some parts of the world.
Biologists are looking at how a shark
in a Great Lakes region aquarium gave
"virgin birth" last year. Photo courtesy of
Belle Isle Aquarium, Detroit.
A female shark in an aquarium in the Great Lakes region has apparently given virgin birth. Four shark eggs hatched last year and three of those babies are now growing normally. As the Great Lakes Radio Consortium’s Celeste Headlee reports, it may be some time before the cause can be determined, but the event is still a surprise for biologists:
A female shark in an aquarium in the Great Lakes region has apparently given virgin birth. Four
shark eggs hatched last year and three of those babies are now growing normally. As the Great
Lakes Radio Consortium’s Celeste Headlee reports, it may be some time before the cause can be
determined, but the event is still a surprise for biologists:
Biologists have a technical term for virgin birth. It’s called parthenogenesis. Doug Sweet is the
Curator of Fishes at the Belle Isle Aquarium in Detroit. He says parthenogenesis is common in
invertebrates and some amphibians.
“Most vertebrate animals, the females will produce eggs even if the male is not around. And it’s
just a matter of… it’s a chemical trick, basically, to get that egg to develop into an individual
without a sperm activating it.”
But parthenogenesis has been totally unheard of for sharks, until now. Last year, the Henry
Doorly Zoo in Omaha, Nebraska, announced they thought a Bonnethead shark there had
reproduced by parthenogenesis. The baby lived less than 12 hours, though, and genetic tests were
But when Doug Sweet saw the press release from the Henry Doorly Zoo about a possible virgin
birth, he thought he’d try an experiment. Sweet decided to incubate the eggs of his two female
bamboo sharks. Four of the eggs developed. Sweet says the sharks were acquired by the
aquarium before they had reached sexual maturity, and they have never been exposed to a male.
He says the likely conclusion is that these sharks are reproducing by parthenogenesis.
Two other explanations, though highly unlikely, are that the shark has both testicular and ovarian
tissue, and fertilized its own eggs or that sharks are capable of storing sperm for years and even
passing it down to their offspring. Sweet has sent small clippings from the sharks’ fins to the
Henry Doorly Genetics Lab. Testing has already begun, but Sweet says it could take more than a
year to get the results. In the meantime, Sweet says the facts remain the same: a female shark
has given virgin birth. If it is parthenogenesis, he says, it will have important implications for
biologists around the world.
“Parthenogenesis just hasn’t been considered to happen in sharks; it’s never been recorded. It may
be happening all the time out there, so this is kind of breaking news in the shark world.”
The two adult bamboo sharks and the offspring are currently on exhibit at the Belle Isle
Aquarium in Detroit.
For the Great Lakes Radio Consortium, I’m Celeste Headlee.
Are sperm counts on the decline? Federal researchers hope they can find out. The government is about to launch the largest project ever to find out if something’s gone wrong with male reproductive health. The study will follow a recent report from the California Department of Health Services that startled the scientific community. The study found a significant drop in sperm count and raised questions about whether environmental chemicals are the culprit. The Great Lakes Radio Consortium’s Julie Edelson Halpert has more: