Ephippium

Part of speech: noun

Definitions

1. A hardened, saddle-shaped covering found on some insect larvae or fish eggs that protects developing embryos
2. A protective, saddle-like structure formed on eggs or larvae of various aquatic species to shield them during development
3. A rigid, saddle-shaped casing associated with the eggs or early stages of some animals, serving as a defense mechanism

Etymology: The Greek word "ephippion" meant "saddlecloth," a cloth laid over a horse's back beneath the saddle. It was built from "epi," meaning "on" or "upon," and "hippos," meaning "horse," so the literal sense is something set on a horse. The Romans borrowed it as "ephippium" with the same sense, and it kept that horse-related meaning for centuries. The jump to biology came much later. Zoologists adopted the Latin word for the saddle-shaped egg casing that certain animals produce, most notably the cladoceran water fleas (Daphnia and their relatives), which carry a protective shell around their resting eggs. The shape of that casing resembles a saddle set over the animal's back, so the ancient horse equipment name was carried over to a creature that never saw a horse.

Synonyms: saddle, harness, seat, support, rest