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Arachnids are arthropods in the class Arachnida (/ ... Physiology. There are characteristics that are particularly important for the terrestrial lifestyle of ...
Arachnid locomotion is the various means by which arachnids walk, run, or jump; they make use of more than muscle contraction, employing additional methods like hydraulic compression. [ 1 ] [ 2 ] Another adaptation seen especially in larger arachnid variants is inclusion of elastic connective tissues .
Basic characteristics of arachnids include four pairs of legs (1) and a body divided into two segments: the cephalothorax (2) and the abdomen (3). The ventral side of a brown widow spider. The epigastric plates and furrow are visible, as well as the hourglass marking on the underside of the abdomen, which is a characteristic feature of widow ...
Anopheles stephensi. Arthropodology (from Greek ἄρθρον - arthron, "joint", and πούς, gen.: ποδός - pous, podos, "foot", which together mean "jointed feet") is a biological discipline concerned with the study of arthropods, [1] a phylum of animals that include the insects, arachnids, crustaceans and others that are characterized by the possession of jointed limbs.
Arachnology is the scientific study of arachnids, which comprise spiders and related invertebrates such as scorpions, pseudoscorpions, and harvestmen. Those who study spiders and other arachnids are arachnologists. More narrowly, the study of spiders alone (order Araneae) is known as araneology. [1]
The oldest known arachnid is the trigonotarbid Palaeotarbus jerami, from about in the Silurian period. [101] Note 3 ] Attercopus fimbriunguis , from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, but its lack of spinnerets means it was not one of the true spiders , [ 103 ] which first appear in ...
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Unlike arachnids with book lungs (scorpions, most spiders and several others), harvestmen and most other purely tracheate arachnids lack extensive arterial branching and well-defined venous sinuses. The circulatory system consists mainly of a dorsal tubular heart with anterior and posterior aortae. The heart is innervated by a cardiac ganglion.