Brief but interesting knowledge about the class of organisms called the Crustacea

Brief but interesting knowledge about the class of organisms called the Crustacea

Three-fourth of all animal species belong to the Phyllum Arthropoda. The name 'arthropod' comes from two Greek words, arthros, jointed and podes, feet. All members of the Phylum Arthropoda share the following characteristics:1. Arthropods have jointed appendages. Appendages are extensions of the body and include legs, mouthparts of various kinds and antennae.2. The arthropod body is segmented. A pair of appendages is attached to each segment. In some species, the appendages have been lost or reduced in size during the course of evolution. The members of some classes of arthropods have many body segments. In others, the segments have become fused together into functional groups, or tagmata (singular, tagma), such as the head or thorax of an insect, by a process known as tagmatization, which is of central importance in the evolution of the arthropods. All arthropods have a distinct head, sometimes fused with the thorax to form a tagma called the Cephalothorax.3. Arthropods have an exoskeleton. This is a hard external covering that provides protection and support.4. Arthropods have a ventral nervous system, an open circulatory system, a digestive system, and specialized sensory receptors.The Phylum Arthropoda is divided into three subphyla: Chelicerata, Crustacea, and Uniramia. The chelicerates are characterized by Chelicerae, mouthparts that often take the form of pincers or fangs, which evolved from the anterior appendage. Members of the other two subphyla have mandibles, originally biting jaws that also evolved from appendages, but from the second or third pair back from the anterior end. All appendages in Crustaceans are fundamentally biramous, or two branched, whereas those in Uniramia are uniramous, or single branched.Medical Arachnoenthomology studies the representatives of Phylum Arthropoda, which have medical importance, The members of this phylum can be the provisional or constant parasites of human beings, the infection carriers, and the poisonous animals. Phylum Arthropoda includes three classes of medical importance:1. Class Crustacea: Cyclops and crabs

2. Class Arachnida (Octapoda): Scorpions, spiders, ticks and mites

3. Class insecta (Hexapoda): mosquitoes, flies, bugs, lice and fleas.Class Crustacea

Most crustaceans have two pairs of antennae, three pairs of chewing appendages, and various numbers of pairs of legs. All of the appendages of crustaceans, with the possible exception of the first pair of antennae, are basically biramous. Crustaceans differ from the insects in that they have legs on their abdomen as well as on their thorax. They are the only arthropods with two pairs of antennae. Most crustaceans are small. Copepods no larger than a comma inhabit the surface waters of oceans, lakes, and streams. Large primarily marine crustaceans such as shrimps, lobsters and crabs, along with their freshwater relatives the crayfish, are collectively called decapod crustaceans. The term decapod means "ten-footed". Most of their body segments are fused into a cephalothorax, which is covered by a dorsal shield, or carapace, which arises from the head. The crushing pincers common in many decapod crustacenas are used in obtaining food, for example, by crushing mollusk shells. Crabs differ from lobsters and crayfish in proportion: their carapace is much larger and broader, and the abdomen is tucked under it. Shrimps and their relatives also have different proportions; their carapace is proportionately smaller than that of lobsters or crabs.Subclass Entomostraca (Cyclops, diaptomus, and eudiaptomus)

They are 1-3mm, pear shaped; body is divided into cephalothorax and abdomen. Cephalothorax is 50 segmented and carries a single median eye, 2 pairs of antennae (17 and 4 segmented), 4 pairs of legs. Abdomen has 4 segments in female, 5 segments in males, ends by two branches (each branch has 2 bristles).Medical importance:

Cyclopes are intermediate hosts of the fish tapeworm (Diphyllobothrium latum) and Draculus medinensis. Subclass Malacostraca (crabs and other decapod crustaceans). Crab is second intermediate host of the lung fluke (Paragonimus westermani).I am Funom Theophilus Makama. I advertise through writing. As a platinum expert Author, I write lots of articles and hence promote interested websites, companies, groups, organizations, and communities through publishing and distributing my articles. For more information on this interesting venture, click on the link belowhttp://funom-makama.blogspot.com/2010/07/advertising-contracts.html

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