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Alphabet Game 2021


Pariah

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Ribbon worms, or nemerteans, are a group of very unusual worms related to mollusks and annelids. Most ribbon worms live in the ocean, and some can grow to over 100 feet long, but are usually much less than an inch wide. Some species live on land or in freshwater. Unlike annelids, ribbon worms are not segmented.

 

The proboscis of the class Anopla exits from an orifice which is separate from the mouth,[9] coils around the prey and immobilizes it by sticky, toxic secretions.[20] The Anopla can attack as soon as they move into the range of the proboscis.[21]Some Anopla have branched proboscises which can be described as "a mass of sticky spaghetti".[9] The animal then draws its prey into its mouth.[10]

 

In most of the class Enopla , the proboscis exits from a common orifice of the rhynchocoel and mouth. A typical member of this class has a stylet, a calcareous barb,[9] with which the animal stabs the prey many times to inject toxins and digestive secretions. The prey is then swallowed whole or, after partial digestion, its tissues are sucked into the mouth.[20] The stylet is attached about one-third of distance from the end of the everted proboscis, which extends only enough to expose the stylet. On either side of the active stylet are sacs containing back-up stylets to replace the active one as the animal grows or an active one is lost.[9] Instead of one stylet, the Polystilifera have a pad that bears many tiny stylets, and these animals have separate orifices for the proboscis and mouth, unlike other Enopla.[22][23] The Enopla can only attack after contacting the prey.[21]

 

Nemerteans generally move slowly,[10] though they have occasionally been documented to successfully prey on spiders or insects.[35] Most nemerteans use their external cilia to glide on surfaces on a trail of slime, some of which is produced by glands in the head. Larger species use muscular waves to crawl, and some aquatic species swim by dorso-ventral undulations. Some species burrow by means of muscular peristalsis, and have powerful muscles.[9] Some species of the suborder Monostilifera, whose proboscis have one active stylet, move by extending the proboscis, sticking it to an object and pulling the animal toward the object.[22]

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