BEARDWORM

also called Pogonophoran, any of a group of marine invertebrates constituting the phylum Pogonophora. Pogonophorans live a sedentary life in long, protective tubes on seafloors throughout the world. The common name beardworm refers to the beardlike mass of pinnate (feather-like) tentacles borne at the anterior end of many species. An intestine, which forms in embryos, disappears as development progresses. Males of the phylum are generally similar in appearance to females. Pogonophorans are the only multicellular animals that have neither mouth nor anus. Pogonophorans were first classified as a distinct phylum in the middle of the 20th century. The first species, Siboglinum weberi, described in 1914, came from the seas of the Malayan Archipelago; the second species, Lamellisabella zachsi, which came from the Okhotsk Sea, was described in 1933. In 1937 a new class called Pogonophora was established for Lamellisabella. In 1955 a close affinity between Siboglinum and Lamellisabella was proved, and the members were placed in the newly established phylum Pogonophora. Pogonophorans usually inhabit marine waters to depths that exceed 1,000 metres (3,280 feet); some species have been found at depths ranging from 7,000 to 10,000 metres. A native population inhabits the trenches of the Pacific and the Indian oceans. Many genera have a discontinuous distribution.