Synapseidae

Synapseidae is not a widely recognized taxon; the name is a misspelling of Synaptidae, a family of sea cucumbers (holothurians) within the phylum Echinodermata and the class Holothuroidea. The correct name is Synaptidae, and the type genus is Synapta. The family includes several genera of slender, worm-like holothurians. Members typically have elongated bodies, with reduced or absent tube feet along most of the body, and a mouth surrounded by feeding tentacles adapted for deposit or suspension feeding. The skin is often smooth or lightly papillae-covered; calcareous plates are reduced in many species, giving a soft appearance. The best-known member is Synapta maculata, the giant sea cucumber, among the longest echinoderms.

Synaptids have a cosmopolitan distribution, found from shallow tropical seas to deeper temperate habitats, often in soft sediments, seagrass beds, or under debris. They play roles in benthic ecosystems as detritivores and as prey for specialized predators. Pearlfish and certain crustaceans are known to inhabit some synaptid hosts.

Reproduction is sexual, with external fertilization in many species, and development includes free-swimming larval stages typical of holothuroidea, such as auricularia or doliolaria. Molecular phylogenetics has refined synaptid relationships in recent years, but some genus-level delimitations remain debated.

Synaptidae comprises numerous genera and species, and taxonomic work continues to resolve species boundaries and distribution. For further information, consult taxonomic databases such as the World Register of Marine Species.