Bitter Discovery

Student researcher inspired by accidental crab death

Posted: Sunday, August 10, 2008

Kevin MacNeel was not expecting to kill all his research subjects this summer.

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Michael Penn / Juneau Empire
Michael Penn / Juneau Empire

"I will never eat a Tanner crab again," said MacNeel, a University of Alaska Southeast student.

But then again, that's what made it fun.

MacNeel was one of 10 students from around the country who won National Science Foundation-sponsored summer internships with professors at UAS this year. They fished, dove, peered at crab eggs, and painted nail polish on snails for science, and presented the results Thursday at the university. And they learned about how research projects are put together from the first background reading to the often unexpected conclusions.

"Some of it is like a craft," said UAS biology professor Beth Mathews, who runs the NSF program each year. "You can't learn it from a book."

MacNeel had planned a straightforward project on how crab hormones regulate metabolism.

The more you know about the physiology of a crab, what makes it live or die, the better you can predict how environmental factors might affect the commercial fisheries that people survive on here.

But it turned out that all MacNeel's crabs, taken from just outside Auke Bay, had something called bitter crab disease. It's caused by a tiny parasite, a dinoflagellate.

A lot of crabs are carriers. A survey of Kachemak Bay crab found 87 percent of the crab were infected. While that probably affects their survival somehow, it doesn't usually kill them outright, according to MacNeel's mentor, marine biology professor Sherry Tamone.

The parasites do kill the crab, however, when they move on from sticking around in the crab. In an event called sporelation, the crab appears to emit a cloud through its gills. That is the parasites exiting. They destroy the gills as they go.

MacNeel called it a "mind-blowing parasitic event."

He presented a video of a crab sporelating, mucking up the whole tank with the bloom of the parasites.

People can't catch it, as far as anyone knows. Though it can affect the fishery: A crab with a heavy load of dinoflagellates - according to MacNeel, though he had not tried them - has a bitter flavor, something like aspirin.

MacNeel's project had nothing to do with bitter crab disease.

The deal was he would sample hormone levels in the crabs before and after cutting off their eyestalks with sharp scissors.

"This is all really, really standard," MacNeel said, describing the experiment that had been done for many other crustacean species already, just not Tanners.

An eyestalk is for a crab like a human's pituitary gland inside the brain. The eyestalk controls all kinds of body functions such as molting, sex and eating. Without it, the crab molts and eats and so forth without any regulation, and it's also blind, but it doesn't die. Ordinarily.

But in this case, MacNeel unwittingly forced the hand of the parasites, causing them to sporelate and therefore kill their hosts outright.

Now that gummed up the conclusions, which were meant to be drawn from an experiment on healthy volunteers.

That's all right, because MacNeel is planning to stick around in the lab and repeat the same experiment with noninfected crabs.

The unintentional massacre also opens the door for an interesting scientific zigzag: collaboration with other scientists on bitter crab disease, which MacNeel said has been difficult to study in labs.

"I think they carry the disease, and Kevin just found a great way to induce it," said Tamone, his mentor.

MacNeel was not alone in his experience of things not going as planned. One student researcher got a shock out with research divers when a humpback whale upset his skiff. Another student did an experiment on snail predation, but found her results skewed by the snails' inexorable tendency to leave the experimental grounds on their own.

The often jagged route to scientific progress can be the seed of inspiration that starts a scientific career.

"You learn so much more from something going awry than you do from things going your way," MacNeel said. "I mean ... I feel sorry for those crabs."

• Contact reporter Kate Goldenat 523-2276 or

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