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Images: Bacteria Hitchhike on Tiny Marine Life

Amalia Aruda uses a spoon and pipette to select individual tiny marine animals called copepods from a population of copepods cultured in a bucket. Aruda, a graduate student in the Massachusetts Institute of Technology-Woods Hole Oceanographic Institution Joint Program in Oceanography, studies the relationship between copepods and bacteria living on them. (Photo by Ann Tarrant, Woods Hole Oceanographic Institution)

Top view (top) and side view (bottom) of the copepod species Eurytemora affinis, which Aruda studies. On its shell and inside its body this copepod species can carry large amounts of Vibrio cholerae, the bacteria that causes the deadly disease cholera. The side view appears larger than the top view, but the animals are the same size—about 1 milimeter (0.04 inch) long. (Microscope photos by Amalia Aruda, Woods Hole Oceanographic Institution)

Aruda also studies a "large" copepod, Calanus, to discover what kinds of bacteria live on it. These microscope photos show a top and side view of Calanus, a 4 milimeter (0.16 inch)-long shrimp-like crustacean. The marine zooplankton is critical food for larger marine animals, from fish to whales. (Top photo by Chris Linder, Chris Linder Photography. Bottom photo by Mark Baumgartner, Woods Hole Oceanographic Institution.)

In 2012 Aruda (left) accompanied WHOI biologists Ann Tarrant and Mark Baumgartner (right) on a research trip to Norway to study wild and lab-cultured copepods. In the lab of Dr. Bjorn Henrik Hansen at SINTEF, Aruda constructed plastic culture buckets to hold the copepods. (Photo by Ann Tarrant, Woods Hole Oceanographic Institution)

WHOI biologist Ann Tarrant collects a sample of small marine animals from a marsh in Sandwich, Mass. Tarrant, who is graduate student Amalia Aruda's Ph.D. advisor, studies immune and endocrine systems of marine invertebrates including planktonic crustaceans such as copepods. (Photo courtesy of Ann Tarrant, Woods Hole Oceanographic Institution.)