When is a bat like a porpoise?
11/23/2003Bats can hear pitches a half octave higher than most mammals can.
That may not sound like much, until you think of the Star Spangled Banner. It covers one and a half octaves. For most of us, those few extra notes are a ticket to Screechville.
Rickye Heffner, a researcher at the University of Toledo, reports in the journal Hearing Research, that the Jamaican leaf-nose bats and other echolocators - that is, animals that use sound to navigate - have a hearing advantage.
Generally, one can predict how high an animal hears by its head size. But echolocation drives the evolution of hearing further. Not only bats, but porpoises and dolphins - which also echolocate - hear a half-octave higher than average.
The exception proving the rule may be the Egyptian fruit bat, says Gimseong Koay, a research associate at UT Laboratory of Comparative Hearing.
“There are well over 1,000 species of bats worldwide. Of that 1,000, 75 echolocate,'' he said. The Egyptian fruit bat uses a primitive form of echolocation. Rather than use the “soundless” sonar of other bats, it navigates using tongue clicks. It turns out this animal's hearing range is nothing special - about average for its head size.
You have to wonder about a fish that everyone describes as a poor swimmer. So, is it any surprise that even though it split from its kin 5 million years ago, one can barely tell?
The bottom-hugging tubenose goby was first discovered invading the Great Lakes in 1990. Unlike other European invaders, this fish never managed a significant North American population explosion, and is seldom found outside of Lake St. Clair and western Lake Erie.
Carol Stepien of Cleveland State University, compared the genes of tubenose specimens from Europe and Asia.
It turns out, there's a 5-million-year gap between the Black Sea specimens thought to be relatives of our adopted gobies, and gobies from the Danube. In fact, the locals are the same species as the Danube goby.
David Jude, the University of Michigan professor who first discovered gobies in the Great Lakes writes in an email: “I was surprised she found two species.'' Now, he says, he'll need to see how to tell the fish apart without looking at their genes.
A second gene therapy trial for people with poor circulation in their legs begins this month.
In January, the Jobst Vascular Center of Toledo Hospital began testing fibroblast growth factor 1, a substance known to make blood vessels grow. Now, Anthony Comerota of Jobst and Christopher Cooper of the Medical College of Ohio are enrolling patients to test a similar factor, this one called hepatocyte growth factor, produced by the Japanese company AnGes MG Inc.
A quarter of the 100 patients in the nationwide trial will receive placebo in three injections. The rest will receive varying doses of the growth factor. Researchers hope the growth factor will improve circulation, preventing amputations.
-- Jenni Laidman