You are currently browsing the monthly archive for August, 2006.
Well, I meant to post an explanation for my extended absence, but apparently I hit the wrong button in my pre-trip flurry. I have just returned from two weeks in Iceland, where I visited Reykjavík, Vestmannaeyjar (the Westman Islands), and Skaftafell, and saw a great deal of geology, birds, and rain (and a few whales).
Over the next week or so, I will be posting accounts. The post frequency will vary according to how much time I have and how long it takes me to go through the 2.5 GB of photos I took and pick out the decent ones.
Recently introduced Asian shore crab Hemigrapsus sanguineus (left) and the previously-introduced green crab Carcinus maenas (right). Photo: Aaren Freeman/University of New Hampshire.
Researchers at the University of New Hampshire (UNH) have found that native New England blue mussels (Mytlius edulis) have evolved to respond to a recently-introduced predatory crab species in as little as 15 years.
Crabs prey on mussels by crushing their shells, so blue mussels along the New England coast have evolved the ability to thicken their shells in response to the presence of green crabs (Carcinus maenas), which were introduced to the waters 150-200 years ago. The Asian shore crab (Hemigrapsus sanguineus), however, reached New Jersey shores only in 1988, and it has not yet extended its range north of mid-coast Maine.
“This set up a chance to look at populations that had been exposed to the predators for varying lengths of time,” said Aaren Freeman, a doctoral candidate and lead author of the study, in a UNH press release. “We wanted to know, how is it that these mollusks can recognize a crab that is historically not present in North America?”
The scientists found that southern mussels exhibit shell thickening in the presence of Asian shore crabs. Northern mussels do not react to Asian shore crabs.
The study extended over two years and was coducted separately in both in the field and the laboratory for confirmation. “The consistency over two years and two sites really suggests an underlying robust mechanism,” said James Byers, an associate professor of zoology and Freeman’s advisor.
This study has important implications for fishermen, who could perhaps protect the northern mussel populations from Asian shore crabs by mixing in some of the adapted southern mussels.
REFERENCES AND FURTHER READING:
Freeman, A.S., and Byers, J.E. 11 August 2006. Divergent Induced Responses to an Invasive Predator in Marine Mussel Populations, in Science, vol. 313, p. 831-833. [full-text, $]
Potier, B. 10 August 2006. Mussels Evolve Quickly To Defend Against Invasive Crabs. University of New Hampshire. [press release]
There’s a disconnect between the job market and the goals of students and faculty members in the geosciences, according to a recent study by the American Geophysical Institute.
I, for one, am not surprised.
Oil/gas and mining are growing industries, expected to replace 50% of their geoscience technical workforces in the next 10 years. Student goals, however, overwhelmingly favor the environmental industry, followed by state and federal government and academia. Faculty advisors also highly recommend K-12 education, although students are generally less interested in this career path.
The environmental industry makes sense for recent B.A./B.S. graduates, with its abundance of entry-level positions. The upswing in oil industry jobs is relatively recent (what happened to hydrology? Last I heard, that was the hot geoscience subfield). And academia has traditionally had a disdain for private-sector profit-driven industry. Public service–whether with the government, academia, or a nonprofit (and to a lesser extent, environmental consulting)–is more in keeping with the ideals of academia than the oil or mining industries (which traditionally have also had poor job security).
You can tell idealistic college students who make biodiesel during their spare time that they’ll make more money in the oil industry than in the environmental industry, but that doesn’t mean they’ll consider that to be as important as survey administrators.
REPORT:
Baker, Margarent Anne. 2006. Student and Faculty Employment Attitudes in the Geosciences 2006. American Geological Institute, Geoscience Workforce.
A barnacled 10-foot-long manatee estimated to weigh 1,000 pounds is making its way up the Hudson River. The usual habitat of the endangered marine mammal is the waters of Florida, but they have been known to make it as far north as Virginia in summer. This is the first known occurence of a manatee heading up the Hudson.
Manatee with calf. Photo: U.S. Fish & Wildlife Service (public domain).
No photographs of the Hudson manatee have yet been taken, only grainy video, but multiple sightings seem to confirm that the animal is definitely a manatee. Boaters are cautioned to take especially care in shallows so as not to injure it. There are currently no plans to relocate the manatee, as waters will remain warm for a few more weeks.
What I’m most curious about is why it’s heading that far inland into fresher water; manatees generally stay in brackish coastal waters. Increased ocean temperatures may explain part of why individuals like this manatee and the northern bottle-nosed whale stranded in the Thames in January venture so far from their natural territories, but I can’t help but wonder if something went wrong in their brains, too.
References:
Lee, Jennifer. 7 August 2006. Massive Manatee Is Spotted in Hudson River. New York Times.
Norris, Michele. 7 August 2006. Manhattanites in a Manatee State of Mind. NPR. [radio program]
Shapley, Dan. 2 August 2006. Manatee spotted near NYC. Poughkeepsie Journal.
Researchers have found what appears to be organically preserved bone marrow in 10-million-year-old amphibians from the Miocene of Libros, Spain. Postdoctoral researcher Maria McNamara of University College Dublin (UCD), like Mary Higby Schweitzer (who found the T. rex soft tissue last year), found the marrow by accident. Accidental fractures that occured during collection and cataloging revealed the marrow to McNamara, who was looking for other types of soft tissue. The frogs and salamanders were collected from a Spanish sulfur mine which was a subtropical lake 10 million years ago.
Bone marrow is one of the most fragile tissues–it is extremely prone to decay, particularly bacterial. McNamara found evidence of marrow in only 10% of the 56 adult frog fossils and in one of the 15 salamanders. The three-dimensional organic residue retains the original texture and red and yellow color of marrow, as well as vascular structure.
The researchers, an international team from Ireland, Spain, the UK, and the US, attribute the preservation to the protective quality of the bone. “[T]he bones of the amphibians formed protective microenvironments, and inhibited microbial infiltration,” they wrote in the paper, which appeared in the August 2006 issue of Geology, the most widely-read earth science journal. Fossil marrow was extremely rare in the 79 tadpole specimens examined, McNamara noted.
“This find, together with last year’s reports of fossilised blood vessels in Tyrannosaurus rex, sets a new threshold for the kinds of tissues we can expect the fossil record to yield,” said McNamara.
Schweitzer, who found the T. rex soft tissue, is still skeptical. “Maybe it is marrow tissue, maybe not,” she said, according to an article in the journal Science. “It will be interesting to see what their further research shows.”
This study provides a good example of the typical timeframe in science, which isn’t always clear from breathless articles. McNamara, then a Ph.D. student, first spotted the tissue in 2004. She and her colleagues then studied dozens more samples that had been collected from the same locality in the 1950s. The study finally appeared in the August 2006 issue of the journal Geology, but McNamara and the other researchers are still conducting geochemical tests to determine conclusively whether the material is preserved marrow. If Schweitzer’s work is anything to go by, we can probably expect another front-cover paper in about six months.
“The whole subject of DNA preservation in fossils is controversial,” McNamara said in a UCD press release. “We’d be quite happy if we get traces of protein.”
Personally, I’m surprised this paper was published in Geology (the top geoscience journal) and not Science or Nature (the top science journals).
REFERENCES AND FURTHER READING:
McNamara, M.E.; Orr, P.J.; Kearns, S.L.; Alcalá, L.; Anadón, P.; Peñalver-Mollá, E. August 2006. High-fidelity organic preservation of bone marrow in ca. 10 Ma amphibians, in Geology, vol. 34, p. 641-644. [full-text, $]
10 million year old fossil frog yields bone marrow [UCD press release]
Stokstad, Erik. 2 August 2006 “Fossil Bone “Marrow” Found, at ScienceNOW.
