Euplotes gigatrox may look like an insect, but it’s a type of single-celled protist called a ciliate. It has lots of hairlike cilia surrounding its mouth parts (large oval depression, top). This microscope image shows the underside of the cell’s supergiant form.

Euplotes gigatrox has two different forms: regular size and supergiant. This is a side view of the supergiant. It eats its smaller siblings by running over them and jamming them into its mouth. That mouth lurks behind the fringe of hairlike cilia.

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bacteria: (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals). Bacteria are one of the three domains of life on Earth.

behavior: The way something (often a person or other organism) conducts itself or acts towards others.

biologist: A scientist involved in the study of living things.

Caribbean: The name of a sea that runs from the Atlantic Ocean in the East to Mexico and Central American nations in the West, and from the southern coasts of Cuba, the Dominican Republic and Puerto Rico down to the northern coasts of Venezuela and Brazil. The term is also used to refer to the culture of nations that border on or are islands in the sea.

cell: (in biology) The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

develop: To emerge or to make come into being, either naturally or through human intervention, such as by manufacturing. (in biology) To grow as an organism from conception through adulthood, often undergoing changes in chemistry, size, mental maturity or sometimes even shape.

filter: (n.) Something that allows some materials to pass through but not others, based on their size or some other feature. (v.) The process of screening some things out on the basis of traits such as size, density, electric charge.

gene: (adj. genetic) A segment of DNA that codes, or holds instructions, for a cell’s production of a protein. Offspring inherit genes from their parents. Genes influence how an organism looks and behaves.

insect: A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.

insight: The ability to gain an accurate and deep understanding of a situation just by thinking about it, instead of working out a solution through experimentation.

Proceedings of the National Academy of Sciences: A prestigious journal publishing original scientific research, begun in 1914. The journal's content spans the biological, physical and social sciences. Each of the more than 3,000 papers it publishes each year, now, are not only peer reviewed but also approved by a member of the U.S. National Academy of Sciences.

protist: A broad group of mostly single-celled organisms that are neither plants nor animals. Some, like algae, may appear plant-like. Those known as protozoans may appear animal-like. And still others appear fungi-like. More blob-like members of the group are known as amoebas.

sea: An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.

sibling: An offspring that shares the same parents (with its brother or sister).