How do crustaceans differ from arachnids?

1 Answer

Crustaceans and Arachnida are classes of Phylum Arthopoda

Arthropoda : Animals with jointed legs .
Largest phylum .

CRUSTACEA :

  • Habitat - Aquatic
  • Body - Differentiated into cephalothorax (head & thorax are fused) & abdomen. + dorsal cuticular plate Carapace
  • Appendages - 2 pair of antennae, one pair of mandible and generally two pair of maxillae in head. As many as 5 pair of walking legs could be present in thorax, smaller legs for swimming present in abdomen. All appendages in crustacea are biramous**

  • Antennae - 2 pairs

  • Respiration -Since it is acquatic, respiration takes place with the help of gills
  • Excretion - Antennary gland or Green gland

Examples *Crabs , prawns , lobsters , shrimps , cyclops *

ARACHNIDA :
Habitat -Terrestial

  • Body - Body is differentiated into cephalothoroax & abdomen
    (same as crustaceans but carapace is absent ).

  • Appendages - 6 paired 1 pair Chelicereae , 2 pairs Pedipalp & rest 4 pairs walking legs .**

  • Antennae - Absent

  • Respiration - Since it is terrestrial, respiration takes place through book lungs ( appear as an open book )

  • Excretion - Coxal gland

    *Examples - Spiders , Scorpians e.t.c*
    

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