Amazon Research

In the Amazon River, three distinct water types collect to create a uniquely rich breeding ground for extreme aquatic life.

Laurie Anderson Explores How Marine Clams Found Their Way Into one of the World’s Largest Rivers

The Amazon River is teeming with life, from solitary four-hundred-pound catfish to shoals of eight-pound piranha. But in the Amazon basin around Santarem, Brazil—where white water, clear water, and black water rivers pool together—it’s the ancient tiny mollusks that have captured the attention of Mines researcher Dr. Laurie Anderson.

The three distinct water types collect here to create a uniquely rich breeding ground for extreme aquatic life in one of the world’s largest rivers.

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Photo of Dr. Anderson by Mark Siddall, American Museum of Natural History

Anderson’s research interest is in a little known genus of typically saltwater Corbulidae clam from the last member of a once diverse radiation in the western Amazon. She has devoted much of her career to studying this clam and other family members in the fossil record, and her current research continues to explore its evolutionary track.

Anderson, who is also the head of the Department of Geology & Geological Engineering, spent three weeks during the fall living on a boat in the Amazon Basin, collecting aquatic specimens for a National Science Foundation-funded survey on aquatic faunal of the lower Amazon. It was the second such trip she participated in for this comprehensive survey of freshwater macrofauna (larger invertebrate and fish) by a team of thirteen senior researchers from five countries. Anderson is co-principal investigator.

The thorough species inventories of sponges, flatworms, annelids, mollusks, crustaceans, and fishes will result in large collections at premier natural history museums. The research will also produce species description and taxonomic revisions; online and printed guides to the aquatic macrofauna; a guide book to fishes of the lower Amazon; a detailed plan for the long-term monitoring of aquatic diversity in floodplain and forest stream systems; and a Tropical Biodiversity Field Course for US and Brazilian students.

The Amazon’s current course is a relatively recent phenomenon, geologically speaking, she says. Tens of millions of years ago the river drained to the north into the Caribbean.

While the Amazon itself is a white water river, the Brazilian basin where the team has been conducting research is effectively a giant nutrient-rich lake where the clear water Tapajos River and the black water Arapiuns Rivers join. “The Amazon Basin is known for having a number of taxa that we typically think of as marine inhabiting freshwater. This includes my clams but also dolphins, sting rays, needle fish, etc.,” Anderson says.

Eleven million years ago the western Amazon Basin was a large series of wetlands that saw the diversification of several lineages of mollusks, including the Corbulidae, says Anderson, who has published prior research about these clams.

“I am now using the new collections from Brazil to get molecular data to place members participating in this radiation in the evolutionary tree for the family. This marine family has freshwater representatives also in Australia and Asia, and my colleagues and I are trying to determine if these taxa represent a single branch of the evolutionary tree or if members of the family invaded freshwater multiple times in their evolutionary history,” Anderson says.

Last edited 1/3/2017 8:43:26 AM

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