Zoology

The final three phyla in this chapter are the most controversial taxa placed within Protostomia. Evidence that Ectoprocta, Brachiopoda, and Phoronida belong within the lophotrochozoan subgroup of protostomes comes from sequence analysis of the genes encoding small-subunit ribosomal RNA. Some developmental data are consistent with the molecular data: in phoronids, …

Entoprocta (en’ – to-prok ‘-ta) (Gr. entos, within, + proktos, anus) is a small phylum of about 150 species of tiny, sessile animals that superficially resemble hydroid cnidarians but have ciliated tentacles that tend to roll inward. Most entoprocts are microscopic, and none is more than 5 mm long. They …

Gastrotricha ( gas-tro-tri’ -ka) (N. L. fr. Gr. gaster, gastros, stomach or belly, + thrix, trichos, hair) includes small, ventrally flattened animals usually less than 1 mm in length. The largest species of gastrotrichs can reach lengths of about 3 mm. Superficially, gastrotrichs may appear somewhat like rotifers but lacking …

The first and only micrognathozoan , Micrognathozoa specimen, was collected from Greenland in 1994 but not formally described until 2000. Micrognathozoans are tiny animals that are interstitial (living between sand grains) and about 142 µ m long. The body consists of a two-part head, a thorax, and an abdomen with …

Rotifera (ro-tif -e-ra) (L. rota, wheel, fera, those that bear) derivet heir name from the characteristic ciliated crown, or corona, that, when beating, often gives the impression of rotating wheels . Rotifers range from 40 µ m to 3 mm in length, but most are between 100 and 500 µ …

Gnathostomulids are delicate wormlike animals less than 2 mm long . The first known species of Gnathostomulida (nath’o-sto-myu’lid-a) (Gr. gnathos, jaw, + stoma, mouth, L .ulus, dim. suffix) was observed in 1928 in the Baltic, but its description was not published until 1956. Since then jaw worms have been found …

Nemerteans (nem-er -te-ans) are often called ribbon worms. Their name (Gr. Nemertes, one of the Nereids, unerring one) refers to the unerring aim of the proboscis, a long muscular tube  and that can be thrust out swiftly to grasp their prey. The phylum is also called Rhynchocoela (ring -ko-se -la) …

The name Mesozoa (mes-o-zo -a) (Gr. mesos, in the middle+ zoon, animal) was coined by an early investigator (vanBeneden, 1876) who considered the group a “missing link”between protozoa and metazoa. These minute, ciliated, wormlike animals represent an extremely simple level of organization. All mesozoans live as parasites or symbionts in …

Taenia saginata (Gr. tainia, band, ribbon) is called the beef tapeworm, but it lives as an adult in the human intestine. Juvenile forms occur primarily in intermuscular tissue of cattle. A mature adult may reach a length of 10 m or more. Its scolex has four suckers for attachment to …

Schistosomiasis, infection with blood flukes of genus Schistosoma (Gr. schistos,divided, + soma, body), ranks among the major infectious dis eases in the world, with 200 million people infected. The disease is widely prevalent over much of Africa and parts of South America, West Indies, Middle East, and Far East. The …