May 2002

From Smithsonian Institution

Ominous signs of cryptic marine invasions

Common brittlestars jumped the Isthmus of Panama approximately two centuries ago

Cryptic stowaways in fouling communities or ballast water of seagoing ships may look exactly like local marine animals. But a comparison of brittlestars reported in the Proceedings of the Royal Society suggests that human-aided dispersal gradually blurs important genetic distinctions between once-isolated groups.

Globalization of invasive organisms represents a huge, uncontrolled experiment with potentially disastrous environmental and economic consequences.

Lampreys and Zebra Mussels destroyed Great Lakes fisheries; the Nile Perch and Water Hyacinth took over Lake Victoria. But another class of invaders may be wreaking havoc on marine ecosystems undetected by watchful eyes.

Michael Roy and Renate Sponer suspect the ‘world's most common brittlestar', a six armed inhabitant of shallow coral reefs, may have invaded the western Atlantic in fouling communities on ships over the last two centuries.

Genetic markers indicate massive long-distance dispersal and recent mixing of brittlestar populations from the western Pacific and Indian Ocean. Populations in the Eastern Pacific look relatively more isolated and stable.

The brittlestars (Ophiactis savignyi) in the Atlantic sort out into two groups: one that probably evolved over the last 3 million years since the rise of the Isthmus of Panama, and another related to the Indo-Pacific group, which probably represents animals introduced fairly recently.

Despite improved marine paint and faster moving ships, an amazing variety of marine organisms continue to foul bottom surfaces and sea chests of oceangoing vessels.

"We have no idea what the consequences of mixing populations are, since we know almost nothing about the ecological role of these brittlestars, but this result suggests there are likely to be many other cryptic invaders out there--a huge conservation problem," according to Roy.

Michael Roy is Senior Lecturer, Dept. of Zoology, University of Otago Aotearoa-New Zealand. Renate Sponer is a Research and Lab Manager at the Smithsonian Tropical Research Institute, Panama.

Ref: M.S. Roy and R. Sponer. 2002. Evidence of a human-mediated invasion of the tropical western Atlantic by the ‘world's most common brittlestar. Proc. R. Soc. Lond. B Vol. 269:1495, p. 1017, DOI 10.1098/rspb.2002.1977

The Smithsonian Tropical Research Institute (STRI), with headquarters in Panama City, Panama, is one of the world's leading centers for basic research on the ecology, behavior and evolution of tropical organisms.

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