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Fish Cross 'Impassable Barrier' to Traverse Pacific Ocean
By Robin Lloyd
Special to LiveScience
posted: 12 July 2006
08:54 am ET

In "The Origin of Species," Charles Darwin discussed geographic features that could serve as "impassable" barriers to marine organisms living in shallow waters. One of the examples he gave was a 2,500- to 4,300-mile expanse of deep water that comes between the eastern and central Pacific Ocean.

For decades, scientists failed to find any marine species hardy enough to make the trek across the long, cold and dark divide.

Then about 10 years ago, Harilaos Lessios of the Smithsonian Tropical Research Institute (STRI) documented a first exception—two species of sea urchins that successfully make the crossing.

Now he has confirmed another exception—18 species of reef fish [see one and two of them].

. . .

It is still correct to say that the Pacific divide is an effective barrier, Lessios wrote in the research report, but it is now clear that it is "sporadically permeable."

"Darwin was right to call the barrier impassable," Lessios said, "even though there were exceptions that he did not know about."

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