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.
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.