Acorn Barnacle

Associated Smithsonian Expert: Rafael Lemaitre, Ph.D.

Rafael Lemaitre

Dr. Rafael Lemaitre is a Research Zoologist and Curator of Crustacea in the Department of Invertebrate Zoology at the Smithsonian National Museum of Natural History. His research focuses on the taxonomy, systematics, biology, and zoogeography of decapod crustaceans, especially hermit crabs, worldwide. He was born, and grew up, in Cartagena, on the Caribbean coast of Colombia. There he obtained his undergraduate degree in marine biology, and developed a keen interest in the study of decapod crustaceans (crabs, shrimps and lobsters) from Caribbean coral reefs and other tropical habitats. He then obtained his Ph.D. (1986) at the University of Miami, Florida, with a dissertation on the taxonomy of an unusual family of deep-water hermit crabs that have developed remarkable symbiotic associations with coelenterates (anemones and the like). He came to the Museum in 1989, and since then his research has branched out to include primarily the taxonomy and evolution hermit crabs from around the world, both shallow and from the deep sea. He has discovered nearly 100 new species, and published numerous papers on their taxonomy, biology, and evolution. He regularly conducts filed work in various Caribbean sites, and travels to major museums around the world to study collections obtained during deep sea expeditions and thereby complement the information in Smithsonian crustacean holdings.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Tiny, freshwater amphipod (Gammarus roeseli)
Courtesy of Michal Manas, via, CC-BY-SA


About Crustaceans (Subphylum Crustacea): Feeding

Crustaceans have a full toolkit for feeding. On the front of a crustacean’s head are two pairs of sensitive antennae for feeling food. Picture a lobster’s long antennae swinging up and down. Two appendages, often claws, are used to seize food and break it up into pieces. Crustaceans typically have three pairs of biting mouthparts for chewing. The configuration of their mouthparts varies, depending on whether they are predators, scavengers, or filter feeders. While crustaceans have many adaptations for eating, they are also a common prey for other organisms. Humans eat millions of tons of crabs, lobsters, and shrimp every year. Tiny crustaceans, including krill and copepods, are part of the plankton that tend to congregate in the top few hundred meters of the ocean and are are vital to the marine food web. As krill and copepods feed, they concentrate ocean nutrients into their bodies, which then become available to the fish and filter-feeding organisms that prey on them.

The appendages of barnacles (Semibalanus balanoides) are hidden under hard plates
Courtesy of JC Schou, via Biopix, CC-BY-NC

About Arthropods (Phylum Arthropoda): Body Plan

Arthropods are the most successful group of organisms on Earth in terms of numbers, including almost half of all known species. The hallmark of their success is a body plan that makes them durable and adaptable. All arthropods have external skeletons made of hard material (chitin embedded in a protein matrix). The exoskeleton protects them from predators, weather conditions, and other threats. As they grow, arthropods typically shed the exoskeleton to reveal a bigger, fresh one underneath. The two lengthwise halves of an arthropod body are a mirror image of each other (bilateral symmetry) and typically divided into segments. Each segment has appendages that are specialized for the many activities of the arthropod. An arthropod may use appendages to feed (mouthparts), to breathe (gills, tracheae, book lungs), to reproduce (genitalia), and to move around (walking, swimming, flying). Having a modular body plan with multifunctional appendages has allowed arthropods to thrive in an impressive variety of environments.