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SYNOPTIC DESCRIPTION OF THE SUBPHYLUM CHELICERIFORMES

SYNOPTIC DESCRIPTION OF THE SUBPHYLUM CHELICERIFORMES (SCHRAM AND HEDGEPETH 1978)

EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> BILATERIA> PROTOSTOMATA> ECDYSOZOA> PANARTHROPODA> ARTHROPODA> CHELICERIFORMES
SUBPHYLUM CHELICERIFORMES LINKS

Introduction

Hierarchical Classification

The following information came from Margulis and Schwartz (1998), Buchsbaum (1938), Barnes (1980), Barnes (1984), Brusca and Brusca (2003), Hickman (1973), Storer and Usinger (1965), and Tudge (2000).
  • I. SYNONYMS: arachnids, chelicerates, arthropods.
  • II. NUMBER: >63,000 species known.
  • III. SUBPHYLUM CHARACTERISTICS:
    • A. Structure
      • Symmetry: Bilateral; segmented body regions organized into cephalothorax and abdomen.
      • Body Cavity: True coelom reduced and absent in adults. Haemocoel the only body cavity.
      • Body Covering: Covered by chitinous exoskeleton.
      • Support: Hardened exoskeleton.
      • Digestive System: Food tube simple. Mouth at anterioventral end. Flanked by modified legs that serve as mandibles in some and a terminal anus in front of the telson (last body segment).
      • Circulatory System: Open. Haemocoel of blood sinuses with a dorsal heart. Respiratory pigments (haemocyanin sometimes) in the plasma.
      • Locomotion: Six cephalothoracic pairs of appendages: chelae, pedipalps and 4 pairs of walking legs).
      • Excretory System: Malpighian tubules or tubules that discharge at the bases of appendages.
      • Nervous System: Usually, the circumesophagial ring and ventral cords united into brain from which nerves issue directly. Eyes usually simple (compound in some), sensory hairs.
      • Endocrine System:
      • Respiratory System Modifications of appendages that function as gills book gills or book lungs from which tracheae arise.
    • B. Reproduction:
      • Reproductive System: Dioecious. Gonads paired. Fertilization external or internal (by spermatophores). Oviparous.
      • Development: Eggs are centrolecithal. Development does not include larval form that is markedly different from adult.
    • C. Ecology: Mostly free-living predators, terrestrial or marine.
LITERATURE CITED

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By Jack R. Holt and Carlos A. Iudica. Last revised: 02/03/2013
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