Organic and animate artifacts found during the exploration of Rama. Biots were manufactured in a number of varieties, each dedicated to specific maintenance tasks.
The physiology of biots generally consists of a simple musculature, a fairly complex brain, and a battery. The battery is similar to that found in Terran eels and rays and consumes 80% of the biot's body. The battery supplies all the biot's energy needs, so they require no food, water, light or atmosphere. However, their "life expectancy" is unknown.
Although biots are organic in nature, they cannot be classified as a lifeform. Biots have no ingestive, exgestive, or reproductive facilities. The battery provides all life support, new biots are manufactured on an as-need basis.
Each type of biot has a tailored physiology and programmed "instinct". Most prevalent types during the Endeavor expedition to Rama were "crabs" and "spiders." Crabs are multi-legged and amphibious; they serve as scavengers or waste disposal units. Spiders have whip-like legs connected to a large cyclopic head; they serve as mobile scouts.
Since each biot is a special-purpose unit, they require no special tools or instructions to carry out their assigned tasks. (They are, however, reactive to spontaneous commands in a single-minded way.)
The biots were automatically manufactured from raw materials supplied by the cylindical sea (see Rama). As Rama prepared to leave our solar system, the biots returned to the sea for recycling.
From Rendezvous With Rama by Arthur C. Clarke