Arthropoda

Arthropoda

1. ANIMAL KINGDOM PHYLUM ARTHROPODA

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4. Introduction, Other features, Body wall, Digestion, Respiration, Circulation, Excretion, Nervous system, Reproduction Synopsis

5. Introduction

6. INTRODUCTION Arthropod is the biggest phylum. About 9,00,000 species exist Von Siebold established phylum Arthropods. Arthropods are found in water, land, sea, in plant and animals. Phylum includes Crabs, prawn, insets, spider, scorpion, ticks, mite, centipedes, millipedes and fossil arthropods which are called Trilobites.

7. Other features

8. OTHER FEATURES Body is bilateral, triplablastic with organ system level of organisation Head is distinct [High degree of canalization], Consists of many fused segments bears well developed sense organ such as eyes, compound eyes, antennae. Compound eye consist of many similar unit ommatidia each having lens and capable of forming image.

9. OTHER FEATURES Arthropods have various shapes with externally segmented body. Segmentation is either (1) Two region with Head and trunk or Cephalothoras and abdomen (2) Three region with Head, thorax & abdomen Some or all segments bear jointed appendages . Hence name arthro - joints, poda – foot. No internal segmentation like Annelida

10. Body wall

11. BODY WALL Cuticle composed or protein & polysaccharide chitin which is further strengthen by deposition of mineral (calcium phosphate & carbonate) Restricts growth and periodically change during growth known as moulting or ecdysis . Flexible part of cuticle is called suture. Chitinous plates which form exoskeleton are known as sclerites .

12. BODY WALL Single layered epidermis without cilia & flagella. Muscle are arranged in bundles. Muscle are striped/strained - Voluntary (first time developed in arthropods) Due to presence of joints muscle are separate in them Body cavity around viscera contain blood and is called the haemocoel . True coelom is reduced to cavities in reproductive organs (gonads) & excretory organs. Coelom of gonads is called gonocoel and of nephrons is called nephrocoel .

13. Digestion

14. DIGESTION Digestive Tract is complete Involves 3 parts (1) Stomedaeum (Anterior) ( 2) Mesenteron (Middle) (3) Proctodeum (Posterior) Striated muscles are found in digestive tract.

15. DIGESTION Mouth parts adapted for Biting and chewing - Biting and chewing type - Grasshopper, Cockroach, Termites, Caterpillars. Piercing - Sucking type - Mosquitoes, Bugs Chewing lapping type - Bee Sponging type – Housefly, fruitfly Siphoning type – Butterfly, moths

16. Respiration

17. RESPIRATION Respiration is through body surface or special structure such as gills (e.g. Prawn) Trachea (e.g. Insects) Book-lungs (e.g. Scorpion) Book-gills (e.g. King crabs) Trachea carry oxygen direct to the cells

18. Circulation

19. CIRCULATION Circulatory system is Open i.e. blood flows in haemocoel instead of blood vessels. Blood - With white corpuscle, colourless – Hemolymph (e.g. Insect) Copper containing pigment haemocyanin (e.g. Prawn) Heart - A dorsal, tubular pulsatile , one to many chambered tubular structure.

20. Excretion

21. EXCRETION Antennary or green glands or maxillary gland (e.g. Crustaceans) opening directly to the exterior. Coxal gland (e.g. Arachnids) Malpighian tubules (e.g. Insects) opening into the gut. Excretory matter is Ammonia in aquatic animal, Uric acid is land animal.

22. Nervous system

23. NERVOUS SYSTEM Nervous system comprises of a ring and a double, solid midventral nerve cord bearing a pair of ganglia per segment or less (Ganglia).

24. Reproduction

25. REPRODUCTION Insects communicate by Pheromones by releasing chemical into the environment. Also acts on a sex attraction. Sexes are separate. Fertilization internal but few aquatic has external. Gonads have ducts. Larva stage undergoes degree of metamorphosis. Sexual dimorphism may be present. Mostly oviparous few viviparous.

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