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Characteristics of Phylum Arthropoda


1.- Jointed appendages; ancestrally, one pair to each segment, but number often reduced; appendages often modified for

     specialized functions.


2.- Living in marine, freshwater, and terrestrial habitats; many capable of flight.


3.- Free-living and parasitic taxa.


4.- Bilateral symmetry; segmented body divided into functional groups called tagmata: head and trunk; head, thorax,            and abdomen; or cephalothorax and abdomen; definite head.


5.- Triploblastic body.


6.- Reduced coelom in adult; most of body cavity consisting of hemocoel (sinuses, or spaces, in the tissues) filled with           blood.


7.- Cuticular exoskeleton; containing protein, lipid, chitin, and often calcium carbonate secreted by underlying                      epidermis and shed (molted) at intervals; although chitin occurs in a few groups other than arthropods, its use better      developed in arthropods.


8.- Complete digestive system; mouthparts modified from ancestral appendages and adapted for different methods

      of feeding; alimentary canal shows great specialization by having, in various arthropods, chitinous teeth,                           compartments, and gastric ossicles.


9.- Complex muscular system, with exoskeleton for attachment, striated muscles for rapid actions, smooth muscles for         visceral organs; no cilia.


10.- Nervous system similar to that of annelids, with dorsal brain connected by a ring around the gullet to a double                nerve chain of ventral ganglia; fusion of ganglia in some species.


11.- Well-developed sensory organs; behavioral patterns much more complex than those of most invertebrates, with                wider occurrence of social organization.


12.- Parthenogenesis in some taxa.


13.- Sexes usually separate, with paired reproductive organs and ducts; usually internal fertilization; oviparous,

       ovoviviparous, or viviparous; often with metamorphosis.


14.- Paired excretory glands called coxal, antennal, or maxillary glands present in some; others with excretory organs            called Malpighian tubules.


15.- Respiration by body surface, gills, tracheae (air tubes), or book lungs.


16.- Open circulatory system, with dorsal contractile heart, arteries, and hemocoel (blood sinuses).




Integrated principles of zoology / Cleveland P. Hickman, Jr. ... [et al.]. – 14th ed. p. cm.

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