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The world’s largest amphipod, Alicella gigantea, feeding at the bottom of the Pacific Ocean. Credit: Alan Jamieson, CC BY-SA 4.0
Sometimes we consider a species rare because it truly is, whether because it’s endangered or simply because it naturally has sparse populations. But other times, a species may only appear rare because it lives in such remote locations that people haven’t managed to find it very often. That seems to be the case with the world’s largest amphipod, Alicella gigantea. Amphipods include more than 10,700 shrimp-like crustaceans found throughout the sea and other aquatic environments. And Alicella gigantea, which can grow to a little over 13 inches long, outsizes them all, but it lives in a very hard-to-reach habitat.
Alicella gigantea live on the deep sea floor, so it’s not surprising that researchers have not seen many of them. But a group of scientists from Western Australia wanted to find out just how rare—or common—these critters might be. They collected all the scientific records they could find for this species since the first specimen was discovered in 1899. They found 195 records from 75 locations throughout the world, including finds in the Pacific, Atlantic and Indian oceans. And it turns out, the large white crustaceans can live over quite a broad range of the deep sea, at depths ranging from 2.4 to 5.6 miles below the surface.
Knowing the conditions where the species lives, the researchers then estimated that similar habitat is present in more than half of the entire ocean floor—somewhere around 59% of it. Just as remarkably, when they analyzed the makeup of the specimens that had available genetic data, the scientists discovered that the Alicella gigantea amphipods were genetically very similar to one another from vastly different locations. That means huge swaths of the deep ocean floor throughout the world might be crawling with these huge crustaceans—making them not so rare after all.
