Posted: 23 Jun 2010 11:35 AM PDT
While the oil disaster's terrible toll on birds and turtles will at least be measured, less charismatic creatures tend to be ignored. That's why conservationists are organizing a citizen science project to count the Gulf Coast's ghost crabs.
Also known as sand crabs, they're not classically cute, but they're an important part of coastal food webs. Because the crabs are relatively easy to spot, it's possible for people to help scientists estimate their numbers, providing baseline counts for comparison against future surveys.
"A lot of people are speculating that this spill could have severe effects on marine invertebrates," said Drew Wheelan, a conservation coordinator for the American Birding Association, who came up with the idea for a ghost crab count. "Ghost crabs are conspicuous and easy to count."
Wheelan modeled his project after an ongoing Gulf Coast bird count organized by the Audubon Society and Cornell Lab of Ornithology. Since early May, birders have submitted approximately 150,000 observations from Gulf states. That data will be invaluable to scientists trying to quantify the oil's impacts, especially in areas where precise population counts didn't previously exist.
University of Florida zoologist Sea McKeon designed the ghost crab-counting methodology, which is described on Wheelan's blog, along with instructions for submitting data. It involves measuring distances between tideline crab burrows at a specific time and place each day for as long as possible, and requires little more than a measuring tape, notebook and pen, GPS reading and some sunscreen.
Wheelan said counts need to start as soon as possible in areas where oil hasn't yet come ashore. Pre-disaster data is needed, and BP — which is trying to bar journalists and citizens from many affected areas — may close beaches as oil approaches.
Wheelan is still counting birds, too. During an ABA film project, Wheelan was interrogated by a policeman who appeared to take orders from BP.
But for now, "at least in Florida and Alabama and Mississippi, people are still able to travel on beaches" and count crabs, said Wheelan.
Image: Drew Wheelan
Posted: 23 Jun 2010 08:47 AM PDT
Two genes found only in fish may be a key piece in the puzzling evolution of limbs.
The genes' removal from zebra-fish embryos resulted in the loss of actinotrichia — a basic fin component — and made their proto-fins resemble appendages seen in ancient fossils of the first four-legged creatures.
"The loss of actinotrichia may have contributed to the evolutionary transition from fin to limb," wrote researchers led by University of Ottawa biologists Jing Zhang and Marie-Andrée Akimenko in a study published June 23 in Nature.
During early embryonic development, fins and limbs look strikingly alike. In fish, however, some cells form a pattern of fine fibers. These are the actinotrichia, which form the scaffold on which fin rays are assembled.
In their study, Zhang and Akimenko noticed that two genes, actinodin 1 and 2, are especially active during zebra-fish fin development. These proved to code for previously unknown proteins that mix with collagen to form actinotrichia.
Subsequent searches of animal-genome databases found the actinodin genes in other bony fishes (including whale sharks, living fossils little changed in the 400 million years since the Devonian, before limbs evolved) but not in mammals, birds or amphibians.
When the researchers knocked actinodin genes out of zebra-fish embryos, actinotrichia didn't form in the resulting fishes' pectoral fins. Their tails, however, were unaffected. That fits with the evolutionary narrative suggested by fossils of the earliest known four-limbed creatures, which kept their fishy tails even as legs started to form.
Similar general patterns of gene expression are also found in embryonic chickens and mice with extra toes, a condition known as polydactyly.
"This is also in agreement with the fossil record, which indicates that the earliest primitive aquatic tetrapods of the late Devonian were polydactylous," wrote the researchers.
Image: Left: A zebra-fish–embryo fin. Right: The paw of an embryonic mouse.
Citation: "Loss of fish actinotrichia proteins and the fin-to-limb transition." By Jing Zhang, Purva Wagh, Danielle Guay, Luis Sanchez-Pulido, Bhaja K. Padhi, Vladimir Korzh, Miguel A. Andrade-Navarro & Marie-Andree Akimenko. Nature, Vol. 465, No. 7301, June 23, 2010.
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