How do crustaceans differ from arachnids?
Crustaceans and Arachnida are classes of Phylum Arthopoda
Arthropoda : Animals with jointed legs .
Largest phylum .
- 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 *
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*