ARTHROPODA (III): filter feeding; remaining subphyla
a) filter feeding at small size is difficult because of high viscosity: water has no momentum, 'wall effects' are large, flow is reversible
b) in fairy shrimp a filter box forces water through a sieve of setae
a) 2 tagmata, bear chelicerae in place of 1st antenna, uniramous legs
b) Cl. Pycnogonida: 1pr. ovigers, 4pr walking legs, tiny abdomen
c) Cl. Merostomata: 'living fossils', only 4 living species; 5pr walking legs (first 4 with claws), abdominal book gills, tail spine
d) Cl. Arachnida: most diverse class; 1pr. pedipalps, 4pr walking legs, abdomen lacks walking legs, compound eyes lost
a) 3 tagmata; head with 1pr. antennae & 4pr. legs like thoracic legs
b) variable number of thoracic segments with similar biramous limbs
c) variable number of abdominal segments fused as pygidium
a) 2nd antennae lost, uniramous limbs, spiracle/trachea system
b) SupCl. Myriapoda: 2 tagmata, trunk with many similar legs, compound eyes lost
- Cl.Chilopoda: 15 - 177 pr of legs; 1st pair bear poison claws; mostly predatory
- Cl. Diplopoda: 100 - 700 pr of legs; adjacent trunk segments fuse yielding 2pr legs per body unit (diplopodia); mostly herbivorous
c) SupCl. Hexapoda: 3 tagmata, 2nd maxillae fuse as labium, thorax with 3 pr. walking legs, abdomen lacks limbs
- Cl. Apterygota: insects lacking wings
- Cl. Pterygota: winged insects
- SubCl. Exopterygota: hemimetabolous life history
- SubCl. Endopterygota: holometabolous life history
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Copyright © 1997 by A. Richard Palmer. All rights reserved.(revised March 26, 1997)