The sea mouse, Aphrodita aculeata, is a marine polychaete worm found in the North Atlantic, the North Sea, the Baltic Sea and the Mediterranean. The sea mouse normally lies buried head-first in the sand. It has been found at depths of over 2,000 metres (6,600 ft).
The name of the genus is taken from Aphrodite, the Ancient Greek goddess of love. This is because, when viewed ventrally, the animal resembles a human female's genitalia. The English name may either have a similar meaning, or may derive from the supposed resemblance to a bedraggled mouse when washed up on shore. The specific name aculeata is the Latin for spiny.
The body of the sea mouse is covered in a dense mat of setae (hairlike structures). Adults generally fall within a size range of 7.5 to 15 centimetres (3.0 to 5.9 in), but some grow to 30 centimetres (12 in). They have been described as scavengers, but are known to be active predators on other polychaete worms, both active and sedentary species, including Pectinaria and Lumbriconereis, feeding by night; prey is swallowed whole, head first, and long prey like the king ragworm Nereis virens take a long time to ingest.
The sea mouse is categorized as an active predator, feeding primarily on other polychaete worms,small crabs and hermit crabs. The only time when the sea mouse becomes active is during the night, once it has buried itself in the sand. In cases where it attacks larger prey, they are consumed head first, while being pressed slowly into the intestines to be digested. The sea mouse has been observed consuming other polychaete worms over three times its own body length.
The spines, or setae, on the scaled back of the sea mouse are one of its unique features. Normally, these have a deep red sheen, warning off predators, but when the light shines on them perpendicularly, they flush green and blue, a "remarkable example of photonic engineering by a living organism". This structural coloration is a defense mechanism, giving a warning signal to potential predators. The effect is produced by many hexagonal cylinders within the spines, which "perform much more efficiently than man-made optical fibres".
- WoRMS: Aphrodita aculeata Linnaeus, 1758
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