Lec. 19 respiretory system.ppt
- 1. R K PANSE Assistant Professor Entomology
- 2. Introduction Gas exchange by complex tracheal system. Trachea made by integuments. Absent in collembolla, protura, chironomids of endoparasites of hymenoptera and Diptera. Ectoderm in origin.
- 3. Organs of respiration Internal tubular structure Tracheal branches, trunk & commissures Air scas Tracheoles External orifices structure Spiracles
- 5. In the insect respiration takes place through Trachea, Tracheoles and Spiracles. Trachea: Exchange of gases takes place through tubular structures, called trachea. They are distributed throughout the body collectively forming tracheal system. Trachea are fine elastic tubular structures which are ectodermal in origin. They consist of cuticle, epidermis, basement membrane as in case of general body wall but arranged in reverse manner, i.e. basement membrane forms the outermost coat of trachea. The inner cuticular lining forms the intima inside.
- 6. The cuticular lining (intima)appear as a spiral thickening throughout the length of the tube of trachea. These spiral thickenings are known as ‘taenidia’ which give support to the trachea without being collapsed when there is no air. It consists of chitin, resilin in protein-chitin matrix. Tracheoles :The trachea are divided in to very fine branches known as tracheoles. They supply oxygen to the body tissues.
- 7. Differences between trachea and tracheoles: Trachea Tracheoles These are large tubes running from spiracles Fine tubes arising distally from trachea Taenidia present Absent Intima layer is shed during moulting Intima layer is retained, unchanged during moulting Never become intracellular Intracellular The intima layer consist of protein –chitin matrix with resilin Chitin – protein matrix present, resilin absent
- 8. Tracheal trunks The trachea coming from spiracles join with those of neighbouring spiracles forming ‘longitudinal trunks’. These trachea by combining with those coming from dorsal, lateral and ventral sides of the body fuse to form transverse commissures and longitudinal connectives. All these in total form into dorsal trunk, lateral trunks and one ventral trunk. The dorsal trunk supply oxygen to proximal part of the body as well as to heart, whereas the ventral supplies to the central nervous system. The two lateral longitudinal trunks spreads tracheoles to alimentary canal, legs, gonads and wings. As the head, air is supplied through the first pair spiracles by means of two main branches of the dorsal longitudinal trunk, where one branch supply O2 to eyes, antenna, brain; other branch to mouthparts and muscles of the head.
- 9. Spiracles: These trachea open outside on the body wall through small openings called spiracles. A total of 10 pairs are present in general, 2 pairs in thorax and 8 pairs in abdomen. Spiracles are situated on pleural surface. They consists of a small ring like sclerite at opening called ‘peritreme’ leading to a cavity known as ‘atrium’ . The closing and opening of spiracles is accompanied by atrial valve lined with fibrous processes and form so called felt chamber which reduces water loss in the absence of closing mechanism.
- 10. On the basis of structure, spiracles are divided in to following types 1. Simple spiracle 2. Atriate spiracle 3. Bichambered spiracle 4. Biferous spiracle 5. Multiferous spiracle
- 11. Classification of tracheal system based on number and arrangement of functional spiracles In most of the insects, 10 pairs of spiracles are present. Some of the modifications are as follows: I. Holopneustic : 1 + 1 + 8 e.g. dragonflies, grasshoppers II. Hemipneustic : One or more pairs of spiracles become non- functional. They are a) Peripneustic : 1 + 0 + 8 e.g.: larvae of Lepidoptera, b) Amphipneustic : 1 + 0 + 1 e.g: larva of Diptera. c) Propneustic : 1 + 0 +0 e.g.: mosquito pupa d) Metapneustic : 0 + 0 + 1 e.g.: mosquito larvae e) Apneustic: No functional spiracles. e.g: mayfly larva, Odonata nymph. III. Hypopneustic : 1 or 2 pairs of spiracles completely absent e.g.: Siphunculata, Mallophaga IV. Hyperpneustic : More than 10 pairs of spiracles are present e.g.: Japyx sps. (dipluran)
- 12. Other types of respiration 1. Cutaneous respiration : e.g.: Protura, Collembola and endoparasitic insects. 2. Tracheal gills: e.g.: larva of Trichoptera, nymphs of Ephemeroptera Also called as abdominal gills 3. Spiracular gills : In some aquatic pupae, 4. Blood gills: larva of Trichoptera 5. Rectal gills: In dragonfly nymphs (naids) 6. Air sacs 7. Plastron respiration: e.g.: aquatic beetles. 8. Abdominal gills 9. Caudal gills
- 14. Function: To respiration. To prevent water losses