Each segment is covered on dorsal side by a convex tergal plate and a ventral thin sternal plate. Digestive System 4. The bladder occupies the innermost region and is drawn into a narrow tube to open to the exterior through the renal aperture on the inner side of the coxa. It divides immediately into a supraintestinal and a sternal artery. Part or all. The last part of the alimentary canal. Cephalic Appendages (Fig. They end in branches in the hepatopancreas. Each lateral groove is bounded by a supporting rod and a ridged plate, both cuticular, on the inner and outer side, respectively. The terminal end of each vas deferens forms a club-shaped swelling, known as seminal vesicle, which opens to the exterior by the male gonopore on the inner side of the coxa of the 5th walking leg. Marine water prawn is called Penacus'. The first five pairs, i.e. Here, the sharpness of the image is dependent upon the number of ommatidia involved and the degree of their separation. Such as- Cephalic appendage (five pairs), Thoracic appendage (eight pairs) … Appendages are divided into three groups according to their position of attachment. With the telson it forms the powerful tail fin. The size is variable, the average being 15 to 20 cm. The body of Prawn is elongated, hemispherical and slightly tapering at the posterior end. 3. ii. All these send out nerves which supply the respective organs (Fig. Arising from the posterior end of the pyloric stomach it runs backward, ascending between the two lobes of the hepatopancreas to reach the dorsal groove in the abdomen beyond cephalothorax and runs posteriorly to end in the rectum in the last segment. In the first pair of abdominal appendages the appendix interna is absent. The food is churned by the cuticular plates of the cardiac stomach and the fine particles, filtered by the comb plates, reach the lateral grooves and finally guided to the ventral chamber of the pyloric stomach. It is placed near the base of the eye stalk. A small, anteroposteriorly compressed chamber, next to mouth, bearing irregular internal folds. They are a pair, one in each antennule, located in the cavity of the precoxa or the basal segment. The cornea is divided into a large number of square facets, each corresponding to a single ommatidium. The two basal segments represent the coxopodite and basipodite and the remaining five are ischium, merus, carpus, propodus and dactylus, respectively, in order of succession. It is proposedthat the biramous limbevolved throughthe basal fusion ofadjacent pairs ofancestrally uniramous appendages. 3.7 Prawn Rostrum Eye Cephalothorax Abdomen Telson Antenna 21 Exercise 3 (viii) At the end of the last abdominal segment, a terminally pointed structure, telson , is present. It is proposed that the biramous limb evolved through the basal fusion of adjacent pairs of ancestrally uniramous appendages. iv. The basal part of the ommatidium is made of spindle-shaped, transversely striated structure, the rhabdome, which is surrounded by seven elongated cells, the retinular cells. The first two pairs are chelate. A tactile seta (Fig. Welcome to NotesOnZoology.com! In bright light, they are extended and in weak light they are retracted. Three longitudinal canals, two laterals and one median, run along the axis. It runs obliquely to the ventral region of the body either through the right or left side of the midgut. By the apposition-of those points of images in a number of ommatidia an erect image of the object is formed. Change of place in prawn takes place in three ways: The body is kept straight in a horizontal position. In the females during breeding season the appendix interna of opposite appendages unite and carry eggs. Haemolymph from the arteries is finally received into minute intercommunicating body spaces, the lacunae, which ultimately open into two large spaces, the ventral sinuses, situated lengthwise in the ventral region, beneath the hepatopancreas. Visualization and feature extraction of the surface morphology of the abdomen of red swamp crayfish The end sac and glandular mass extract excretory products which are carried to the bladder. 1. From the apex of the heart proceeds anteriorly a slender, median ophthalmic artery up to the root of the oesophagus. The incisor process shows 3 teeth. A small epipodite is present. From the inner margin of the endopodjte a small appendix interna arises. 2. The pleopods act like oars. A small nerve arising from the posterior border of the brain connects the two ganglia behind. Appendix internae form a basket in female to carry eggs. Small in size, the lateral walls form prominent folds, imperfectly dividing the cavity into two — a small dorsal and a large ventral chamber. Excretory System 8. What parts of the body does the carapace cover in crustaceans? Thoracopod setae omitted for clarity. In the simplest condition, each segment of a crustacean posesses one pair of biramous appendages (see image, left). Feeding and Digestion 5. The gill is attached to the body about the middle of its length, and is highly vascular. Pleopod:One of the biramous paired appendages typically arising ventrally from each of the anterior five abdominal somites. 3. 13 pairs of paired, biramous appendages are present in the cephalothorax. The appendages of prawn are many-jointed. Delicate setae are present on both the upper and posterior surfaces of the plate. The renal sac acts as a temporary reservoir for waste products. 2). Two delicate connectives join the anterior visceral ganglion with the two commissural ganglia on the circumaoesophageal connectives. In the second to fifth pleopods, appendix internae are present. There are 19 pairs of appendages in palaemon. A biramous limb, however, branches into two, and each branch consists of a series of segments attached end-to-end. Abdomen bears six pairs of appendages. i. The excretory organs consist of a pair of cream-coloured antennary glands with their ducts, a median renal sac and a transverse communicating duct. Almost parallel rays falling on each ommatidium from an object, reach the rhabdome and an image of a point of the object is formed. 25.5). The residue reaches the rectum and egested through the anus. All the crustaceans are exclusively aquatic and found in both freshwater and saltwater habitats. 14D). It then pierces through the thoracic ganglionic mass of the ventral nerve cord and divides into two branches. Five pairs; each leg consists of seven podomeres or segments. 25.10). The haemolymph in the respiratory organs gives up CO2 and absorbs O2. Two pairs of nerves arise from each abdominal ganglion and innervate the corresponding muscles and appendages. The sternal artery is a large vessel. The last pair of abdominal limbs is frequently different from the others and is called the uropod s. The walking legs move in harmony during walking. The two ducts are again connected by a narrow transverse duck Posteriorly, the renal sac ends blindly at the region of the gonad. Following structure constitute the foregut. Each gill-plate is made up of a double layer of cuticle with a single layer of cells in between. This is resorted under emergency. Tearing and passing the food to the mouth. 6. These are called pleopods or swimmerts. The crystalline cones, capable of adjusting accordingly, act in unison and behave as a single unit and the whole of the retinal portion act as a single retina. 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