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The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma (cephalothorax). [1] It is a distinctive feature of the subphylum Chelicerata ( arachnids , horseshoe crabs and others).
The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. [1] The terms prosoma and opisthosoma are equivalent to cephalothorax and abdomen in some groups.
Spiders, unlike insects, have only two main body parts instead of three: a fused head and thorax (called a cephalothorax or prosoma) and an abdomen (also called an opisthosoma). The exception to this rule are the assassin spiders in the family Archaeidae, whose cephalothorax is divided into two parts by an elongated "neck". In the majority of ...
The chelicerate body plan consists of two tagmata, the prosoma and the opisthosoma – excepting the mites, which have lost any visible division between these sections. The chelicerae, which give the group its name, are the only appendages that appear before the mouth. In most sub-groups, they are modest pincers used to feed.
Like other Arachnida, a tarantula's body comprises two main parts, the prosoma (or cephalothorax) and the opisthosoma (or abdomen). The prosoma and opisthosoma are connected by the pedicel, or pregenital somite. This waist-like connecting piece is actually part of the prosoma and gives the opisthosoma a wide range of motion relative to the prosoma.
The prosoma is covered by the carapace and always bears a pair of median eyes. [1] In the probably basal families Palaeocharinidae, Anthracomartidae [30] —and perhaps also Anthracosironidae—there is an additional pair of lateral eye tubercles which, at least in palaeocharinids, [31] appear to have borne a series of individual lenses.
Tagmata and major appendages of a spider: cephalothorax or prosoma and abdomen or opisthosoma The number of tagma and their names vary among taxa . For example, the extinct trilobites had three tagmata: the cephalon (meaning head), the thorax (literally meaning chest, but in this application referring to the mid-portion of the body), and the ...
The heavy-bodied abdomen (or opisthosoma) exhibits a narrow pedicel, or waist, where it attaches to the prosoma. Curiously, there is a complex coupling mechanism between the prosoma and opisthosoma. The front margin of the opisthosoma tucks into a corresponding fold at the back of the carapace.