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MORPHOLOGY

MORPHOLOGY. PRAWNS are small crustaceans, typically between 2 and 25 centimetres long. they are more adapted for swimming than walking.

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MORPHOLOGY

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  1. MORPHOLOGY PRAWNS are small crustaceans, typically between 2 and 25 centimetres long. they are more adapted for swimming than walking. The body of the shrimp is divided into two main parts: the head and thorax which are fused together to form the cephalothorax, and a long narrow abdomen. The shell which protects the cephlathorax is harder and thicker and is called the carapace. The carapace typically surrounds the gills, The rostrum, eyes, whiskers and legs also issue from the carapace. ROSTRUM is a rigid forward extension of the carapace, and can be used for attack or defence. Two bulbous eyes on stalks sit either side of the rostrum. These are compound eyes. Two pairs of whiskers (antennae) also issue from the head.

  2. Appendages • Eight pairs of appendages issue from the cephlathorax. The first three pairs, the maxillipeds,the next five pairs form the ten decapod legs, the pereiopods. • The first five segments each have a pair of appendices on the underside, which are shaped like paddles and are used for swimming forward. The appendices are called pleopods or swimmerets, and can be used for more purposes than just swimming. • The sixth segment terminates in the telson flanked by two pairs of appendages called the uropods. The uropods allow the shrimp to swim backwards, and function like rudders, steering the shrimp when it swims forward.

  3. Digestive system • It comprises of alimentary canal & digestive gland .Alimentary canal consists of Buccal cavity opening with mouth ,Oesophagus ,Stomach ,Intestine &Rectum opening outside by anus . • Digestive gland consists of hepatopancreas

  4. Nervous system It consists of Central Nervous System,Peripheral Nervous System and Autonomous System Central nervous system includes supraoesophageal ganglion ,a pair of circumoesophageal connectives and a double nerve cord. Peripheral nervous system consists of paired nerves that arise from central nervous system.

  5. Excretory system Antennary glands or green glands and a median renal sac are excretory organ of prawn. Antennary glands are located in coxae of the antennae

  6. Male Reproductive System • Testes: • The two testes are soft, white and elongated bodies which fuse at their anterior ends to form a common lobe. • In between them a cardio-pyloric strand, connecting heart to pyloric stomach is situated. Histologically, each testes consists of a coiled and thin walled serriiniferons tubules embedded in connective tissue. • Each tubule is lined with germinal epithelium, the cells of which undergo spermatogenesis to form spermatozoa. A mature sperm consists of a large nucleus and a tail like blunt process. • Vas deferentia: • A long coiled and narrow tube, the vasa deferens arises from each testis near its posterior end. They form a coiled mass and run downwards between the abdominal flexor muscles on the inner side and thoracic wall on the outer side. • Vesiculaseminalis: • Near the base of fifth leg vas deferens swells to form a club-shaped vesiculaseminalis. They store spermatozoa in the form of white compact bodies called spermatophores. • They open outside through male genital pore situated on the inner side of coxa of fifth walking leg of its side.

  7. Male reproductive system

  8. Female Reproductive System • Ovaries: • The two ovaries are white compact and sickle-shaped bodies touching each other at both the ends but leaving a gap in the middle for the passage of the cardio-pyloric strand. • The size and shape of ovaries vary with age and the season of year. Each ovary is enclosed within a membranous capsule and is made of numerous radial rows of ova in various stages of development. Mature eggs are centrolecithal. • Oviduct: • A short, wide and thin walled tube, called the oviduct, originates from the outer middle border of each ovary. • It opens outside through a female genital aperture on the inner side of the coxa of third walking leg of its side. • Life history and development: • The breeding season of Prawn occurs during May, June and July. The male deposits spermatophores near the genital opening of the female and the eggs get fertilized as they come out. • Thus fertilization is external or in-situ. After fertilization eggs remain attached to the pleopod through the sticky secretion of certain tegumental glands. During breeding season a female carries the bunches of eggs in this way until they hatch.

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