Aphroditidae Family of Sea Mice

Two Sea Mice of the Aphroditidae Family can be found in this Website:

Phylogeny:  Sea Mice of the Aphroditidae Family are segmented worms of the phylum Annelida. They are in the class Polychaeta meaning that they are covered with “many bristles”. Sea Mice are in the order Phyllodocida and the suborder Aphroditiformia. Aphroditidae is one of six families in this suborder. The Aphroditidae Family is composed of seven genera and around one hundred and four species.

Morphology:  Sea Mice are best described as a short stout worm with a fur coat. They have  an elliptical outline with a flattened profile. The dorsal side of their body is covered with many bristles which are chitinous setae, spines, or chaetae that assist the animal with movement, swimming, or anchoring. These spines are poisonous and arranged laterally and when threatened they can be raised and fixed in position. Normally these setae have a red sheen, believed to warm off predators, but in light can flush green and blue. The setae are composed of millions of submicroscopic crystals that reflect and filter the faint light at ocean depths. Their backs bear 15 pairs of raised scales. They have a protrusible proboscis that may have zero, one, or two sets of jaws. Their prostomium (first body segment) is globular with one to five pairs of medium-sized antennae, a facial tubercle and, if present, one to three pairs of eyes on stalks. The prostomium is globular with medium antenna, facial tubercle and if present 2 pairs of eyes on stalks. The thick layer of dorsal notosetae (felt-like hairs) gives them a mouse like appearance, hence the common name “sea mice.” Their bodies are composed of 40 ringed segments. Their body cavities are filled with coelemic fluid which, hydrostatically, provides rigidity to the body. Annelids have well-developed circulatory, digestive, and nervous systems. Under their iridescent spines, Sea Mice may be bronze, brown, black, or yellow in color. Sea Mice reach a maximum of 30 cm (12 inches) in length.

Distribution:   Most Sea Mice are free-living, but some live in tubes, burrows, or as parasites inside other animals. They are found on and buried within mud and sand at depths between 2 m (6 feet) and 1,830 m (6,000 feet). They are difficult to locate as they are often covered with silt covered matted setae. Sea Mice are found in tropical, temperate, and polar seas. Sea Mice are a common by-catch of shrimp trawlers. Those from the Atlantic and Mediterranean are well known and fairly well studied scientifically. In contrast, those from the Pacific are not. Four species from the Aphroditidae Family are found in Mexican waters of the Gulf of Mexico and ten are found along the Pacific Coast.

Reproduction:  Sea Mouse reproduction is diverse and poorly documented. Sea Mice are generally gonochoric (male or female for life) but some are simultaneous hermaphrodites (having both male and female reproductive organs). They reproduce sexually with most species engaging in broadcast spawning with external fertilization. Some species have internal fertilization and some species brood their fertilized eggs under their scales until they hatch.

Ecosystem Roles:  Sea Mice are scavengers and predators that prey upon crustaceans, such as crabs and hermit crabs, or on other polychaetas some of which can be three times longer than themselves. In turn they are preyed upon by fish. Some Sea Mouse species, in the north eastern Pacific, play host to a commensal bivalve, the Wrinkled Montaculid, Neaeromya rugifera. The setae of Sea Mice have applications in nanotechnology in that they function as nanowires. Spines from sea mice are known to cause long term damage to joints, bones and muscle tissue in humans. Handling of Sea Mice should be done with caution and medical attention should be sought if spines break off under the skin.