BIOL 317 Lecture Notes - Lecture 9: Metathorax, Desiccation, Nepidae
Document Summary
Spiracles: external openings; hypothetically one per segment, normally occur on meso and metathorax and abdominal segments 1-8 (none in head, prothorax or genital segments) Trachea: series of air-filled tubes; unique to insects, entirely separate from the circulatory system, lined with cuticle. Extensively branched (e. g. 39% of body volume of the june. Insect trachea: tracheal trunks: longitudinal tubes connected to the main tubes from the spiracles, taenidia: spiral cuticular thickening running through trachea, prevents collapsing under reduced pressure, tracheoles: smallest diameter tubes, < 1 micron in diameter (0. 2-1. 0). No cell in an insect is more than 1 cell away from a tracheole. In flight muscle (high o2 consumption) tracheoles extend between muscle fibres. In between, co2 is stored in the hemolymph as bicarbonate. This creates negative pressure and air is sucked into the trachea. When co2 conc. in the trachea > 6. 5%, spiracles relax and co2 is expelled. Arrangements of spiracles: holopneustic all spiracles functional (meso, metathorax, abdominal seg.
