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An order of the cnidarian which includes the fresh-water hydras, the attached and usually colonial hydroids, and many of the smaller jellyfish. It is the largest order of the class Hydrozoa.
Industry:Science
An order of the crustacean superorder Syncarida, the most primitive of the Eumalacostraca. The families Anaspididae and Koonungidae have living representatives, while the Clarkecarididae are true fossils. The families Gampsonychidae and Palaeocarididae, formerly included in this order, now are assigned to a new order, Palaeocaridacea. The Anaspidacea arose during the Paleozoic Era, and the recent species are now restricted as living fossils to fresh-water habitats in Tasmania and South Australia (not New Zealand). They exhibit a great adaptability to special habitats. The first thoracic somite is incorporated with cephalic tagmata.
Industry:Science
An order of the division Spenophyta, subkingdom Embryobionta. The Equisetales, commonly known as horsetails, is represented by a single living genus, <i>Equisetum</i>, with about 25 species found both in moist and dry habitats. These plants grow throughout the world, except in Australia and New Zealand. The plants range from herbaceous to shrubby and rarely exceed 3 or 4 ft (0.9 or 1.2 ft) in height, although some tropical species grow much taller.
Industry:Science
An order of the gastropod subclass Opisthobranchia containing a thousand living species of herbivorous sea slugs; sometimes called Ascoglossa. They occur in all the oceans, at shallow depths, reaching their greatest size and diversity in tropical seas.
Industry:Science
An order of the gastropod subclass Opisthobranchia containing about 2500 living species of carnivorous sea slugs. They occur in all the oceans, at all depths, but reach their greatest size and diversity in warm shallow seas. In this, the largest order of the Opisthobranchia, there is much evidence indicating polyphyletic descent from a number of long-extinct opisthobranch stocks. In all those lines which persist to the present day, the shell and operculum have been discarded in the adult form. In many of them the body has quite independently become dorsally papillate. In at least two suborders these dorsal papillae have acquired the power to nurture nematocysts derived from their coelenterate prey so as to use them for the nudibranch's own defense. In other cases such papillae (usually called cerata) have independently become penetrated by lobules of the adult digestive gland, or they may contain virulent defensive glands or prickly bundles of daggerlike calcareous spicules. So pervasive are the tendrils of the converging lines of evolution that the precise interrelationships between the dendronotacean, arminacean, aeolidacean, and doridacean suborders may never be fully understood.
Industry:Science
An order of the green algae (Chlorophyceae), also called Caulerpales, Codiales, or Siphonales, in which the plant body (thallus) is a coenocytic filament (tube or siphon). The filaments may be discrete with free or laterally coherent branches, or organized into a dense plexus exhibiting distinctive morphological features. Septa, which are generally infrequent and incomplete, are formed by centripetal deposition of wall material. A large, continuous central vacuole restricts the cytoplasm to a thin layer just beneath the wall. The cytoplasm contains innumerable nuclei, discoid plastids, and other organelles. Pigments are similar to those in higher plants but include two distinctive xanthophylls, siphonein and siphonaxanthin. Some genera have distinct plastids for the storage of starch. The chief constituent of the wall is frequently xylan or mannan, polysaccharides in which the monomer is xylose and mannose, respectively. Vegetative reproduction is common, usually by rhizomes or fragments. The life history, known for only a few genera, comprises either one somatic phase, with meiosis occurring in the production of gametes, or an alternation of strikingly dissimilar somatic phases, with meiosis occurring in the production of zoospores. Motile gametes are biflagellate, while zoospores have a subapical crown of flagella. Reproductive cells may be formed in unmodified or slightly modified portions of the filament or in special organs.
Industry:Science
An order of the Holotrichia which contains many species that often are of small size and fairly uniform ciliation. Primarily, these protozoa are of importance as the first possessors of a definite, though inconspicuous, buccal ciliature. This ciliature consists of an undulating membrane on the right side of the buccal cavity and an adoral zone of membranelles that is primitively composed of three membranelles on the left side. This tetrahymenal, or four-part, buccal ciliary apparatus is considered the fundamental condition from which the oral ciliature of many subsequent higher groups evolved.
Industry:Science
An order of the Insecta, commonly called termites, with the general characteristics and stages of other exopterygote insects. They are closely related to the Blattodea. Indeed, the only wood-eating cockroach, <i>Cryptocercus</i>, has a similar collection of protozoa in its hindgut to that of the primitive termite <i>Zootermopsis</i>. Similarly, the Australian <i>Mastotermes</i>, though socially complex, is considered the most primitive extant termite by reason of its having an anal lobe in the adult wing; this character is found throughout the cockroaches.
Industry:Science
An order of the liverwort subclass Marchantiidae. Characteristic features include the differentiation of upper and lower tissues of the gametophyte, ventral scales, and rhizoids of two kinds. The sporophyte is considerably reduced, and the capsule dehisces irregularly. The archegonia, though dorsal, come to be pendant from an elevated receptacle because of differential growth resulting in decurved margins. The stalks of the receptacles are modified branches often with rhizoids in one, two, or rarely four furrows along their length. The order consists of 12 families grouped in two suborders, the more complex Marchantiineae and the simplified Ricciineae.
Industry:Science
An order of the Paracanthopterygii, a fish superorder of questionable monophyly. Percopsiforms are identifiable by the following combination of characters: nonprotractile premaxilla; tooth-bearing ectopterygoid and palatine bones; absence of a suborbital shelf, orbitosphenoid, and basisphenoid bones; weak spines usually present in the dorsal fin; and pelvic fins, if present, behind the pectoral fins. There are three families, seven genera, and nine species, all confined to freshwaters of North America.
Industry:Science
