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No. 94: Jul-Aug 1994

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Those Strange Antarctic Fishes

Notothenioid fish from Antarctic waters
A representative Notothenioid fish from Antarctic waters. (From: Eastman, Joseph T,; Antarctic Fish Biology, San Diego, 1993.)
In the frigid waters ringing the continent of Antarctica live approximately 275 species of fishes, 95 of which are assigned to the suborder Notothenioidei. This particular group of fishes is renowned for its unusual adaptations, as outlined below by D. Policansky:

"Some of them have glycoprotein antifreezes in their blood, some have no hemoglobin, some have so small a temperature tolerance that they die at temperatures above 4�C, some are neutrally buoyant despite lacking swim bladders, and some live as deep as 2950 meters. The suborder has no known fossils, largely because no bony feature -- indeed, no single character of any sort -- can be used to define it. How did these animals arrive there, what are their ancestors, how do they make a living in such an environment, and how can they support commercial harvests?"

(Policansky, David; "Southernmost Fauna," Science, 264:1002, 1994.)

Comment. Those species lacking hemoglobin in their blood are doubly perplexing: (1) Zoologists still do not know how sufficient oxygen is transported in these fishes, for what substitutes for normal blood seems inadequate; (2) How could they have evolved from hemoglobin-carrying fishes? and (3) Why switch from hemoglobin at all when other Antarctic fishes find it perfectly satisfactory?

From Science Frontiers #94, JUL-AUG 1994. � 1994-2000 William R. Corliss