The new species of nototheniid fish, Cryothenia amphitreta, is detailed in the December issue of the quarterly journal Copeia. Paul A. Cziko, a research specialist who had graduated with bachelor’s degrees in animal biology and biochemistry from Illinois six months earlier, and research diver Kevin Hoefling, discovered it in McMurdo Sound in the Ross Sea region of Antarctica in November 2004.

They were diving in the area in search of eggs laid by naked dragonfish (Gymnodraco acuticeps) for a study, published earlier this year, about levels of antifreeze proteins in newly hatched notothenioids in the salty icy waters where the temperature is rarely above the freezing point of seawater.

“We just came across this fish,” Cziko recalled. “It was just sitting on the bottom, like most other fish in the area. There are only about a dozen species that swim in the area, with four to five easily distinguishable species. This one jumped out at us. First of all it was pretty big, and it looked quite different than the others.”

Cziko and Hoefling guided the egg-laden fish into a mesh bag and surfaced.

“It was about twice as big as what you normally see swimming around,” said Arthur L. DeVries, a professor of animal biology who many years earlier had discovered antifreeze proteins in notothenioids. “Its profile was much different than other common local notothenioids. Its center part is much higher. Most of the other species in the area have big heads and have bodies that taper back narrowly.”

Cziko and co-author Chi-Hing (Christina) Cheng, professor of animal biology, studied the purple-gold-colored fish, comparing its measurements and perch-like appearance with all known species of fish that inhabit the icy waters of Antarctica. X-ray radiographs of bone structures were taken at the U. of I. College of Veterinary Medicine.

The new fish, which DeVries theorizes may have been looking for a place to lay its eggs in a flat, clear area near an intake pipe that feeds water into the McMurdo Station, was placed into the genus Cryothenia because of its overall similarity to the notothenioid Cryothenia peninsulae that has only been found near the Antarctica Peninsula.

Although bigger in pelvic-fin length and body size, as well as having more vertebrae, what sets C amphitreta apart from C. peninsulae is head morphology, specifically in the area between the eyes.

The new fish has a “wide, well-defined, two-holed interorbital pit divided by a raised medial ridge, scales anterior to this depression in the interorbital region, and a dark pigmentation of the mouth, gill and body cavity linings,” Cziko and Cheng wrote.

The species name was chosen to help researchers easily distinguish the two species in the genus Cryothenia, which translates from Greek as “from the cold,” while amphitreta literally means “an orifice with two openings.”

“Even though we know a lot about Antarctica,” Cziko said, “we still don’t know everything about the ecosystems and the animals in them. There’s probably a lot more to be learned about how these fish evolved and survived.”

The area where C. amphitreta was found is the most-frequented location in McMurdo Sound explored by divers and fished with hand lines. DeVries has been going to the site for more than 40 years.

The new fish was located on a large flat rock in water that was minus 1.91 degrees Celsius and 20 meters deep.

“Art has been swimming there for more than 40 years,” Cziko said. “You’d think he would have caught everything.” DeVries does have an Antarctic fish named after him: Paraliparis devriesii.

National Science Foundation grants to Cheng and DeVries funded the research.

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