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Images: Salps Catch the Ocean's Tiniest Organisms

Kelly Sutherland, now a postdoctoral scientist at CalTech, and Larry Madin, her doctoral advisor at WHOI, studied the feeding and locomotion of salps, such as this one preserved in a jar. With MIT professor Roman Stocker (not shown), they showed that salps are able to catch and eat some of the smallest particles in the ocean. (Photo by Tom Kleindinst, Woods Hole Oceanographic Institution)

Transparent tubular animals, salps produce a feeding net of mucus that hangs inside their bodies. As they swim, they catch food particles on the net. (Photo by Larry Madin, Woods Hole Oceanographic Institution)

The green-stained mucus feeding net of a salp, photographed under a microscope, reveals amazingly regular openings only about 1.5 microns (1.5 millionth of a meter) on a side. The net catches particles that don't fit through the mesh, but its strands also catch much smaller particles, down to the size of bacteria.
(Photo by Kelly Sutherland, Woods Hole Oceanographic Institution)

Working on living salps requires an ocean-going ship or a lab near open ocean water. Kelly Sutherland, while a graduate student at WHOI, did her research  at the Liquid Jungle Lab in Panama. There, deep water is not far from shore, and Sutherland could collect them by scuba diving. (Photo by Andrew Gray, UC Santa Cruz)

Salps can be connected in long chains of identical animals, all swimming together. In this way, they feed efficiently by filtering food from the water they swim through. (Photo courtesy of Kelly Sutherland, Woods Hole Oceanographic Institution)

Kelly Sutherland doing an experiment with living salps in the Liquid Jungle Lab, Panama. She fed them particles of known sizes to determine what their feeding nets could capture. (Photo by Alexandra Techet, Massachusetts Institute of Technology)

Marine life ranges in size from viruses, at nanometers (10-9m), to whales tens of meters long. The bigger the organism, the fewer there are in the ocean. In general, creatures in one size range  prey on the next range below them. But salps' unique feeding nets catch not only the next size down, but also some of the tiniest and most abundant cells in the sea.