Enoplan nemerteans are typically found in the sea, in the littoral among algae. While larger species may be found simply by turning over boulders, smaller species are not found unless special techniques are utilized. An easy way of collecting nemerteans is to place seaweed and smaller algae in a bucket of sea water and let it stand for a few hours, and up
to a couple of days, depending on weather and temperature. The worms will crawl to the sides of the bucket, where they are easily observed and collected, as the oxygen concentration decreases in the water. Although nemerteans are abundant, especially in temperate waters, their presence is often overlooked because they are not easily observed. Enoplan nemerteans do not appear to be equally common sublittorally, but this may be a result of biased sampling (less accessible environments). The majority of enoplan ribbon worms are marine and benthic, but there are approximately 100 named and described species of pelagic nemerteans. These creatures inhabit the water column of the world oceans, commonly found at depths of between a few hundred feet (meters) and several thousand feet (meters), and they are most abundant at 2,130-8,200 ft (625-2,500 m). There are a few freshwater species recorded, of which most are placed in the genus Prostoma. This genus is also by far the most widespread, especially the two species, P. eilhardi and P. graecense. The latter has been recorded from Europe, Africa, Japan, and Australia. The spreading of these animals is probably a result of the exportation and importation of freshwater vegetation. There are 13 known species of terrestrial nemerteans; a typical feature of these species is that their distribution tends to be restricted to a particular island. These species live in damp places under stones and among rotting woods.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.