Torquaratoridae (Latin for “neck plow”) is a family of Hemichordata that lives in deep waters. They can grow up to three feet in length and have gelatinous bodies, often brightly colored. Cilia on their underside is used to glide over the ocean floor at about 3 inches an hour while detritus is sucked into their gut, leaving behind a constant trail of feces. When deciding to move to new feeding locations, they empty their gut and drifts over the bottom, aided by an excreted balloon of mucus, before they let themselves down somewhere else. One species (Coleodesmium karaensis) has been shown to care for the offspring by bearing about a dozen embryos surrounded by a thin membrane in shallow depressions on the surface of the mother's pharyngeal region. The proboscis skeleton is reduced to a small medial plate in one genus, while it is absent in the remaining species, and the stomochord reduced in adults. Their large eggs, which measures almost 2 millimetres across, suggests that there is direct development without larvae. Their genitals are unusual by being located outside the body. On each side of the worm a flap of the skin runs the entire length of the trunk. Located on the inner surfaces of these flaps, the numerous ovaries and testicles bulges outwards in an epidermal pouch attached to the rest of the body by a slender stalk. The ovaries' eggs are protected by just a single layer of cells. One species, Yoda purpurata, is also the first known hermaphroditic hemichordate. It is assumed these modifications are an adaptation to life in their deep sea habitats.
Only one known species is muscular and robust enough to burrow into substrates. The other species have a very reduced body musculature and are too gelatinous and fragile to do so. Instead they are living directly on the seafloor. The extra-wide-lipped species shows the most obvious adaptations to the free living lifestyle, and are found almost exclusively on rocks of deep-sea lava formations.
At depths between 1500 and 3700m, these animals are often the most numerous along with echinoderms, molluscs, crustaceans and fish.
- From the Field: A Key Player in Evolutionary Biology has a New Family in the Deep Sea
- Karen J. Osborn, Andrey V. Gebruk, Antonina Rogacheva, Nicholas D. Holland (2013). "An Externally Brooding Acorn Worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian Arctic". The Biological Bulletin. 225 (2): 113–123. PMID 24243964.
- Osborn et al. (2011). "Diversification of acorn worms (Hemichordata, Enteropneusta) revealed in the deep sea" (PDF). Proceedings of the Royal Society, B. 279: 1646–1654. doi:10.1098/rspb.2011.1916.
- Observations on torquaratorid acorn worms (Hemichordata, Enteropneusta) from the North Atlantic with descriptions of a new genus and three new species
- Morphology of a new deep-sea acorn worm (class Enteropneusta, phylum Hemichordata): a part-time demersal drifter with externalized ovaries
- Zoologger: First animal with ovaries on the outside
- Diversification of acorn worms (Hemichordata, Enteropneusta) revealed in the deep sea
- New creatures from the deep identified by Aberdeen scientists
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