BSC 2011L Lecture Notes - Lecture 6: Tracheal Tube, Trilobite, Myriapoda
Ecdysozoa – Protosome Group
- Arthropoda
o Insects, crustaceans, chelicerates, and myriapods
o Posses a jointed cuticle made of various salts and chitin
o Cuticle is often referred to as an exoskeleton
▪ Which provides protection, structural support, reduces
moisture lost, and provides surface for muscular attachment
o Metamerism: segmented units
o Open circulatory system
o Cephalization
o Some use gills to breath
o Most insects exchange gases with air using tracheal tube system
o Trilobita
▪ Extinct, ancient arthropods that existed during the pelozoic era
▪ Display characteristics of arthropods
• Chitin exoskeleton
• Fused segments
• Branched appendages
▪ Dorsoventrally flattened and divided into 3 longitudinal
segments
• 2 lateral lobes
• 1 ventral lobe
▪ Average less than 10cm in length
o Chelicerata
▪ Crabs, arachnids, sea spiders
• Arachnids: spiders, ticks, and mites
o Terrestrial
o Chelicerae are modified as fangs to pierce prey
o Pedipalps to manipulate food and sense
environment
o 4 pair of walking legs
o Book lungs and or tracheal tubes for gas exchange
o Two body regions and 8 legs
o Internal glands that secrete silk
