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A Predator in Miniature

IsopodScanning electron micrograph (SEM) of Excorallana sexticornis (Richardson, 1901) from Belize, USNM 205618.

What may look like a Chinese dragon is in reality the head of the quarter-inch long marine isopod crustacean named Excorallana sexticornis (Richardson, 1901). It lives in mangrove habitats in Florida and the Caribbean, temporarily parasitizing fish.

The Scanning Electron Microscope is a tool used by scientists to examine microscopic detail. A beam of electrons strikes the gold palladium-coated specimen and reflects an image that is magnified up to 150,000 times. A photographic print or digital image (a Scanning Electron Micrograph or SEM) of Excorallana sexticornis the result.

Isopod crustaceans are related to the larger and more well-known invertebrates like crabs, shrimps and lobsters. There are more than 10,000 isopod species known world-wide. They are found in all habitats, from the depths of the ocean, shallow coastal marine systems, freshwater streams, springs, and wells, deserts, tropical forests, grasslands and high mountain peaks. They are even found in your backyard. The terrestrial species are commonly known as “pillbugs”, “potato bugs”, “roly-polys” or “woodlice.” Marine isopods can range in size from less than an eighth of an inch to nearly twelve inches long, although most are less than half an inch in length.

They serve the same roles as insects do on land; some are herbivores, some are predators and others consume detritus as well as serving as food for larger invertebrates and fish. A list of all currently known species can be found at this public website:

The Crustacea collection at the National Museum of Natural History (NMNH) is the largest of its kind in the world. This collection occupies six and one-half miles of shelving and contains more than 60 million crustacean specimens from all over the world. Scientists and technicians at the museum study the biodiversity of our planet through such collections in order to help everyone understand the natural world and our place in it.

Additional references on isopods:
Barnes, R.D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart & Winston. 1,089
Kensley, B. and M. Schotte. 1989. Guide to the Marine Isopod Crustaceans of the Caribbean.
Smithsonian Institution Press, Washington, D.C. 308 pages.
Sutton, S. L. Woodlice. 1972. Ginn & Co. London. 144 pages.

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