A one-millimeter worm became biology’s favorite lab animal
Caenorhabditis elegans is a transparent soil nematode about a millimeter long, type species of its genus. In 1963 Sydney Brenner proposed it for neuronal development research; by 1974 he was deep into its molecular and developmental biology—launching a model that still dominates labs.
The genus name stitches together Greek words for recent and rod-like, and the species name is Latin for elegant. Émile Maupas first called it Rhabditis elegans in 1900; Osche moved it into the subgenus Caenorhabditis in 1952, and Dougherty promoted that subgenus to a full genus three years later. The worm became the first many-celled creature to have its entire genome read, and in 2019 the first organism whose complete neural wiring diagram was mapped. By 2024 research on it had earned four Nobel prizes.
Its body plan is spare. A tough cuticle encloses a fluid-filled cavity, a pharynx, gut and gonad, but no blood, heart or lungs, and no liver, pancreas or fat tissue either; fat is kept mainly in the skin and intestine. The triangular pharynx works as a muscular pump that grinds bacteria and pushes them straight into the gut. Four muscle bands along the body can bend it only toward the back or the belly, never sideways, except at the head, where each quadrant is wired separately. Exactly 302 neurons, about a third of all body cells, send processes to a nerve ring that acts as the brain.
Gut granules in the intestine glow blue under ultraviolet light, and when a worm dies a wave of blue light sweeps from head to tail, whether death comes from injury or old age. The glowing substance turns out to be a sugar-bound form of anthranilic acid, possibly an antibacterial defense or a shield that turns harmful UV into visible light.
Most individuals are hermaphrodites, essentially self-fertile females that make about 150 sperm per gonad arm during the last larval stage and then switch to eggs. Males turn up roughly once in every few hundred to a thousand worms, arising when X chromosomes fail to separate, since they carry a single X while hermaphrodites carry two. A selfing worm lays about 300 eggs, but mating with a male can push the brood past 1,000, and hermaphrodites favor male sperm when both are stored. At 20 °C the standard N2 strain lives two to three weeks and completes a generation in three to four days.
Source: Caenorhabditis elegans
