Distribution

The tapeworms are widespread throughout the world. They occur in almost all terrestrial, marine, brackish, and freshwater habitats where vertebrate animals live. Their diversity appears to be great but poorly explored at the tropical latitudes (most of the newly described species during the last decade originate from tropical habitats). They also are abundant at the temperate latitudes (e.g., the number of species found in terrestrial and freshwater habitats in Europe exceeds 900, and the number of the species recorded from a small territory such as Bulgaria (southeastern Europe) is 310).

Light micrograph of the scolex (head) and neck of the adult beef tapeworm (Taenia saginata). At upper left are the two rounded structures which are the suckers used to attach the tapeworm to the intestinal wall of its host. The head narrows into a segemented neck. (Photo by ©Alfred Pasieka/Science Photo Library/Photo Researchers, Inc. Reproduced by permission.)

Light micrograph of the scolex (head) and neck of the adult beef tapeworm (Taenia saginata). At upper left are the two rounded structures which are the suckers used to attach the tapeworm to the intestinal wall of its host. The head narrows into a segemented neck. (Photo by ©Alfred Pasieka/Science Photo Library/Photo Researchers, Inc. Reproduced by permission.)

More than hundred species were reported from marine birds and mammals in Arctic and Antarctic habitats.

About one third of the cestode species are parasites of marine fishes, mostly of sharks and rays. Several pseudophyl-lideans were described from deep-sea teleost fishes (e.g., Pro-bothriocephalus alaini was collected at a depth of 2,590-3,350 ft (790-1,020 m), Probothriocephalus muelleri and Phylobythoides stunkardi at a depth between 5,550 and 7,520 ft (1,690 and 2,290 m), all from the North Atlantic).

The cestode orders have cosmopolitan distributions, with three exceptions only. The litobothriideans are known from the Pacific Ocean only, off California, Mexico, and Australia. The nippotaeniideans were recorded from freshwater fishes in Japan, China, Russian Far East, and New Zealand. The haplobothriideans have the most restricted geographical range. The two species of this order occur in North America, in the "living fossil" bowfin (Amia calva).

Essentials of Human Physiology

Essentials of Human Physiology

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.

Get My Free Ebook


Post a comment