Scientists say it's time to rewrite the textbooks. A marine census released Monday revealed that the polar oceans are home to far more species than had previously been thought. The new census, one of several projects of the Census of Marine Life (an international effort to catalog all ocean life), documented 7,500 species in the Antarctic and 5,500 in the Arctic. Researchers were also surprised to learn that as many as 235 species are found in both polar oceans. They say the discovery raises a number of evolutionary questions.

In this photo, sand fleas (amphipod crustaceans) are shown under shore ice in the Beaufort Sea. Ice-associated amphipods are a major food source for Arctic cod, the main prey for ice seals.
(Shawn Harper/University of Alaska Fairbanks.)