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McGraw Hill Financial, Inc. is an American publicly traded corporation headquartered in Rockefeller Center in New York City. Its primary areas of business are financial, publishing, and business services.
A class of the phylum Rotifera characterized by paired gonads and obligately asexual reproduction, found in diverse freshwater habitats worldwide. Bdelloid rotifers are among the most common microinvertebrates, particularly in ephemerally aquatic environments such as rain gutters, bird baths, moss, lichen, and detritus. First observed by A. Leeuwenhoek more than 300 years ago, bdelloids have long been a favorite subject of amateur microscopists and can easily be isolated and observed with a low-power microscope.
Industry:Science
A class of the phylum Rotifera which comprises a group of little-known marine animals. They form a single family with about seven species and are found only in Europe. The Seisonacea are epizoic or possibly ectoparasitic on crustacea, especially on members of the genus <i>Nebalia</i>. They have a very elongated jointed body with a small head; a long, slender neck region; a thicker, fusiform trunk; and an elongated foot, terminating in a perforated disk (see <b>illus.</b>). The Seisonacea differ from other rotifers in a number of characteristics. They have a very reduced corona, a quite aberrant type of mastax (fulcrate), paired ovaries but no vitellaria in females, and paired testes in the males. Furthermore, the sexes are of similar size and development; only one type of egg is produced, and it requires fertilization. The Seisonacea are also larger than other rotifers, attaining up to 0.12 in.(3 mm) in length.
Industry:Science
A class of the plant division Bryophyta, containing plants commonly called granite mosses. The class consists of one order and two families, the Andreaeobryaceae and the Andreaeaceae. The large tapered foot and short, massive seta of the Andreaeobryaceae show possible linkage to the Bryopsida, but the differences seem more fundamental and more significant than the similarities.
Industry:Science
A class of the Platyhelminthes which are ectoparasites of the gills, skin, and orifices of fishes and, less frequently, of the esophageal tracts and bladders of amphibians and turtles. They have conspicuous anterior and posterior holdfasts, the latter usually armed. The terminal genitalia are frequently sclerotized. The group is characterized by sexual reproduction, direct development, and a single host in the life cycle. Egg capsules have terminal filaments.
Industry:Science
A class of the protozoan subphylum Cnidospora. Members of this class, which includes the orders Myxosporida, Actinomyxida, and Helicosporida, are parasites in fish, a few amphibians, and invertebrates. Actinomyxida with four families and Helicosporida with a single species (monotypic) do not contain subordinal categories. The Myxosporida, however, are divided into two suborders, the Unipolarina and Bipolarina.
Industry:Science
A class of the subdivision Basidiomycotina. These microscopic plant-parasitic fungi are commonly known as smut fungi. Many species may have a shorter or longer saprophytic life cycle, capable of yeastlike reproduction. Several nonparasitic yeasts have been identified as closely related to the smuts. About 1500 true Ustilaginales species are known.
Industry:Science
A class of the subphylum Sarcomastigophora, also known as the Phytomastigina. These are the plant flagellates which contain chlorophyll and other pigments, but colorless forms are also included. Grass green is the usually observed color, primarily because the green flagellates are the largest. Those containing an excess of yellow pigments generally are smaller, and fewer species have unusual colors, such as blue or red. Holophytic, saprophytic, and holozoic modes of nutrition occur, and specific chemical components may be demanded by individual species within the group.
Industry:Science
A class of the subphylum Sporozoa. Inadequate information about the structure and life cycles of the members of this class has, for many years, resulted in the organisms being classified as parasites of unknown nature. Electron microscope studies have shown structural similarities between this group and the Telosporea, but characteristics of the Telosporea such as the presence of spores (oocysts) and sexual reproduction have only recently been reported for the Toxoplasmea. These findings will necessitate reclassification of the Toxoplasmea.
Industry:Science
A class of the subphylum Sporozoa. These protozoa are divided into two subclasses, the Gregarinia and Coccidia. All members of the group are either intra- or extracellular parasites, and the life cycles have both sexual and asexual phases. The spores lack a polar capsule and develop from an oocyst. The sporozoite is the usual infective stage which initiates the asexual phase in the life cycle.
Industry:Science
A class of Tunicata which occurs as solitary zooids or, by a process of asexual budding, develops into colonies. Zooids vary in length from a few millimeters to 10 in. (25 cm). Individuals or colonies are invested by a protective covering, the tunic or test, made of polysaccharide material structurally close to cellulose. Beneath the test is the body wall or mantle. Each zooid has two apertures: inhalant (oral) and exhalant (atrial; see <b>illus.</b>). Water currents, created by cilia on the margins of stigmata in the pharyngeal wall, draw water into the branchial sac, where it is filtered and passed out through the exhalant aperture. The entrance to the branchial sac is guarded by tentacles which prevent large particles from entering. Filtration takes place on a mucous sheet secreted by the endostyle; the sheet is passed across the internal face of the branchial sac by ciliary or muscular action and is then rolled into a cord by the dorsal lamina (or by languets). Digestive enzymes are secreted into the stomach, and a pyloric gland, of unknown function, enters at the junction of stomach and intestine. Gonads are hermaphroditic, and may be situated in the loop of the intestine or in the mantle wall.
Industry:Science
