Tag Archives: phylum

Phylum Annelida (an-neli-da) (L. annelus, little ring, ida, pl.suffi x) consists of the segmented worms. It is a diverse phylum, numbering approximately 15,000 species, the most familiar of which are earthworms and freshwater worms (class Oligochaeta) and leeches (class Hirudinida). However, approximately two thirds of the phylum comprises marine worms …

Rotifers are dioecious, and males are usually smaller than females. However, despite having separate sexes, males are entirely unknown in the class Bdelloidea, and in the Monogononta they seem to occur only for a few weeks of the year. The female reproductive system in the Bdelloidea and Monogononta consists of …

Brachiopoda (brak-i-op’ – o-da) (Gr. brachio¯n, arm, pous, podos, foot), or lamp shells, are an ancient group. Although about 325 species are now living, some 12,000 fossil species, which once flourished in Paleozoic and Mesozoic seas, have been described. Modern forms have changed little from early ones. Genus Lingula (L. …

Ectoprocta (ek-to-prok’ – ta) (Gr. ektos, outside, + proktos, anus) contains aquatic animals that often encrust hard surfaces. Most species are sessile, but some slide slowly, and others crawl actively, across the surfaces they inhabit. With very few exceptions, they are colony builders. Each member of a colony is small, …

Members of phylum Acanthocephala (a-kan’ -tho-sef ‘-a-la) (Gr.akantha, spine or thorn, + kephale¯, head) are commonly called “spiny-headed worms.” The phylum derives its name from one of its most distinctive features, a cylindrical, invaginable proboscis bearing rows of recurved spines, by which it attaches itself to the intestine of its …

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 …