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Acorn Worm (Enteropneusta Worm)
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Description: The Acorn worms or Enteropneusta are a hemichordate class of invertebrates, closely related to the echinoderms. There are about 90 known species of acorn worms. Most acorn worms range from 9 - 45 cm (3.5 - 18 in) in length, with the largest species, Balanoglossus gigas, reaching 1.5 m (4.9 ft) or more. The body is made up of 3 main parts: an acorn-shaped proboscis, a short fleshy collar that lies behind it & a long, worm-like trunk. The creatures mouth is located at the collar behind the proboscis. The skin is covered with cilia as well as glands that secrete mucus. Some produce a bromide compound that gives them a medicinal smell & might protect them from bacteria & predators. Acorn worms move only sluggishly, using ciliary action & peristalsis of the proboscis. Many acorn worms are detritus feeders, eating sand or mud & extracting organic detritus. Others feed on organic material suspended in the water, which they can draw into the mouth using the cilia on the gill bars. A groove lined with cilia lies just in front of the mouth & directs suspended food into the mouth & may allow the animal to taste. Acorn worms breathe by drawing in oxygenated water through their mouth. The water then flows out the animals gills which are on its trunk. Acorn worms continually form new gill slits as they grow in size, with some older individuals having more than a hundred on each side. Acorn worms live in U-shaped burrows on the sea-bed, from the s line down to a depth of 10,000 ft. (3,050 m). This particular specimen is a new variety of enteropneust worm that was discovered in the North Atlantic Ocean, attached to the seafloor by adhesive tentacles & feeding on sea-floor sediment.
Uploaded By: femcat38
Date: 11/17/2011
Views: 418
File Size: 29 KB
