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Past Shows
May 14, 2005
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Penis Preference in Mosquitofish
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Female mosquitofish prefer males with larger sex organs (A). But males with smaller sex organs (B) are more likely to escape predation - Courtesy, Brain Langerhans
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It’s something human males are often accused of -- the desire to brag and show off their male endowment. Women may laugh at this desire to strut, but according to Brian Langerhans, a Ph.D. student of biology at Washington University in St. Louis, there are some females who actually like having a large manhood dangled in front of their face: Female mosquito fish, for instance. Mr. Langerhans has found that female mosquito fish prefer males with a larger sex organ. But, the organ cannot be retracted and creates a drag when the fish tries to swim away from predators, making him more vulnerable. This dilemma has caused mosquito fish to evolve sex organs highly variable in size, depending on how big the threat from predators is in their environment.
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Early Diagnosis of Autism
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Siblings of children with autism have a higher risk of having the disorder
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For parents of children with autism, having another child can mean years of nervous hand wringing. Siblings of children with autism have a much higher risk of having the disorder. In most cases autism is not diagnosed until a child is around three, so all parents can do is wait and see if the fate of their second child will be the same as that of their first. But now, Dr. Wendy Roberts and her colleagues have identified a range of very consistent risk markers that can identify children with autism as early as age one. This means parents can find out much sooner, and the child can start therapy sooner -- and earlier intervention often means better results. Dr. Roberts is a developmental paediatrician and the director of the Autism Research Unit at the Hospital for Sick Children in Toronto.
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Tadpole Bail Out
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A snake attacking eggs - Courtesy, Dr. Karen Warkentin |
Life inside an egg is pretty cosy. There's a constant supply of food, protection from the elements and no competition from your neighbours. But there's also a lack of mobility. Which is a problem if you're being attacked by a predator. So the offspring of the Red-eyed tree frog have come up with a clever solution. When the eggs are attacked by a snake, the tadpoles bail out, literally, falling to the pond below. Dr. Karen Warkentin, from Boston University, has discovered the tadpoles can sense the vibrations caused by the snakebite, and use this to decide whether to jump or not.
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Bobbing Crane Heads
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Whooping Crane - Photo by John and Karen Hollingsworth/USFWS
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We've all seen birds walking along the ground, bobbing their heads back and forth. But answering the question, "Why do they do this?" has been difficult. A few years ago, some researchers said that pigeons bob their heads to keep their view of the ground still while they walked. A recent study by Dr. Tom Cronin, from the University of Maryland, has confirmed this result. He's studied head bobbing in Whooping Cranes and discovered they need to keep their heads still while they're looking for food.
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Peregrine Among the Pigeons
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Peregrine falcon - Copyright, Rob Palmer |
Peregrine falcons are among nature's most skilled and deadly predators. Which made it all the more surprising to Dr. Alberto Palleroni that he kept seeing them miss in high-speed attacks on pigeons. Then he realized it was only some pigeons the falcons were missing in their 300km/h dive-bombing raids. The falcons seemed to have terrible difficulty with pigeons with white feathers on their lower backs. Dr. Palleroni thinks this has to do with the bright white flash acting a bit like a bullfighters red cape - distracting the falcons so they aren't watching the pigeons wings, which will tell them which way the pigeon is going to dodge. Dr. Palleroni is a researcher in the Primate Cognitive Neuroscience Lab at Harvard University.
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Question of the Week: Coral Shape
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This week we have a tropical question from Bill Rolls in Emerson, Manitoba, who asks: How do corals determine their distinctive shape? My understanding is that they begin as free-floating entities that anchor themselves to some surface. How do they become brain coral, fan coral, staghorn coral, etc.?
For the answer, we turn to Dr. Mairi Best, a professor in the Department of Earth and Planetary Sciences at McGill University.
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