Respiration: through the gills or general body surface. Each seta has a swollen base and a pointed shaft bearing fine bristles (Fig. Each appendage has a two-jointed basal region called protopodite to which are attached two distal processes, … Ap­pendix internae form a basket in female to carry eggs. 4. The digested food material that is ab­sorbed through the intestinal wall is circu­lated to different parts of the body through lacunae or sinuses. There are thousands of terrestrial species in this phylum, and a large, predominately aquatic subphylum, the Crustacea. 25.2) of Prawn: Each consists of a three- jointed protopodite bearing three many, jointed flagella at the distal end and a statocyst at the base. The exopodite is plate like and it is called Squama. The body is unjoin ted, bears teeth and masticatory lobes known as molar processes and a jointed mandibular palp on the outer surface. The exopodite is broad, and plate like structure. c. A hastate plate (Fig. Following structure constitute the foregut. The protopodite has two segments, coxa and basis. The distal group surrounding the lens and the cone cells constitute the Irish sheath. Sensory setae are arranged in the sac in the form of an oval ring. Leaf-like, with a flat­tened scaphognathite. Crustacean biramous appendages have a basal or first portion referred to as the protopod. It has 3 segmented endopodite. The main functions of haemolymph (blood) are to transport food and oxygen and the elimination of respiratory wastes in general, although a number of other func­tions are complimentary to these. Exopodite is long and unsegmented. Protopodite is 2 segmented. The exopodite is absent. Innervated by nerve fibres from the olfactory branch of the antennulary nerve. The digestive system consists of an alimentary canal and a hepatopancreas or digestive gland (Fig. d. The filter plate and the bristles of the lateral walls of the ventral chamber act as a pyloric filtering apparatus and permits only liquefied food to pass. 2). A short and stout dorsomedian artery arises from the posterior and ventral region of the heart. A biramous limb typically has a basal part, or protopodite, bearing two branches, an inner endopodite and an outer exopodite. Our mission is to provide an online platform to help students to discuss anything and everything about Zoology. The central nervous system consists of a pair of supraoesophageal ganglia, a pair of circumoesophageal connectives, a sub-oesophageal or thoracic ganglionic mass and a double ventral ganglionated nerve cord. The sense organs include eyes, statocysts, tactile organs and olfactory setae. 2. Respiration is a mechanism by which gaseous exchange takes place between the organism and the environment, in which oxygen is taken in and carbon dioxide is given out. In the second to fifth pleopods, appendix internae are present. First 5 pairs are called Cephalic appendages. Both are connected on the sides by pleuron. 2). The last part of the alimentary canal. III Maxillipede : It looks like a walking leg. • The appendages of the successive segments closely correspond in Structure and development The appendages of prawn Are biramous (Each of them has two process Or rami arising basal portion called protapodite) and Segmentented • The two process are outer exopodite and inner endopodite • Their segments are called podomeres • Protopodite is typically 2 segmented Its two … A tapering blade bearing double lin­ear rows of tiny barbs is attached to the distal end of the shaft. 4. Feeding and Digestion 5. The antennules (or first antennae) are generally regarded as true appendages, although they differ from all the other appendages in the facts that they are always innervated from the "brain" (or preoral ganglia) and that they are uniramous in the earliest and in the adults of all sub-classes except the Malacostraca, where they are biramous or sometimes triramous. Beneath the corneagen cells lie four tall cells—the cone cells—the inner borders of which give rise to a refractive crystalline cone. 2. These are thick-walled vessels, through which the heart pumps out its contents—the haemolymph. 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. 25.10). The. Thoracopod setae omitted for clarity. 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. The respiratory organs consist of the lining membrane of the branchiostegite, three pairs of epipodites and eight pairs of gills. External Features of Prawn 2. Cephalothorax contains two pairs of antennae, one pair of mandibles, and two pairs of maxillae. It is placed near the base of the eye stalk. Behind the eyes, the arteries of the two sides anastomose and form a loop, the circulas cephalicus, with which the median ophthalmic artery joins. Ø Basic parts of appendages are protopodite, exopodite and endopodite. The outer feeler is further divided into an inner smaller branch and outer larger branch. A small, anteroposteriorly compressed chamber, next to mouth, bear­ing irregular internal folds. 1. In the abdomen the appendages are attached to small plate, called Epimeron on the pleuron. The apical segment is fused and corresponds to propodus and dactylus. Ø Total appendages 19 pairs, of which 5 cephalic, 8 thoracic, 6 abdominal. The two sinuses are connected with each other at several places. The free end of the distal segment is bluntly rounded and covered with a thin membrane (Fig 25. The food is captured by the chelate legs and brought to the mouth. The first two legs end in chela and the second is the largest. The nervous system of prawn consists of a central nervous system, a peripheral ner­vous system and a visceral or sympathetic nervous system. (Fig. The external branch (ramus) of the appendages of crustaceans is known as the exopod or exopodite, while the internal branch is known … i. Each appendage has a two-jointed basal region called protopodite to which are attached two distal processes, the outer exopodite and the inner endopodite. Planktonic, coxa of trunk appendages provided with gills (Order Diplostraca, Anostraca) Order Diplostraca. 6. 3. Thorax and abdomen have a pair of biramous appendages in each segment. 16-20. The protopodite bears a three-jointed leg-like endopodite and a slen­der un-jointed exopodite. 3. Structurally they are of biramous type but show considerable variations depending on the functions they perform. It is a small chamber, wider anteriorly and nar­rows down posteriorly to open on the ven­tral surface, at the base of the telson. Appendages are divided into three groups according to their position of attachment. 1. A biramous appendage is one that has two branches. The pleopods act like oars. The renal sac acts as a temporary reservoir for waste products. Reproductive System 10. Arises from the anterior part of the supraoesophageal gan­glion, runs forward and sends branches to the antennule and the statocyst of the side. The common examples for crustaceans include prawns, lobsters, shrimps, barnacles, and crabs. It is proposedthat the biramous limbevolved throughthe basal fusion ofadjacent pairs ofancestrally uniramous appendages. Respiratory, masticatory and sending the food to the mouth. As a result, the existing system of homology, in which uniramous and biramous appendages are considered equivalent, may be invalid. 1. Two delicate connectives join the ante­rior visceral ganglion with the two commis­sural ganglia on the circumaoesophageal connectives. The body of Prawn is elongated, hemispherical and slightly tapering at the posterior end. 3. (ix) *There are 19 pairs of jointed appendages, i.e., one pair in each segment. Biramous appendages are nineteen pairs; five pairs in the head, eight pairs in the thorax and six pairs in the abdomen. 25.2) of Prawn: 1. Class 2 Myriapoda (Myrios: ten thousand; podos: foot) Habitat: Mostly terrestrial. A female brine shrimp, Artemia franciscana, viewed from the left. Each segment is enclosed in a hard cu­ticle divisible into a dorsal, convex tergum a pair of lateral pleurons and a ventral sternum. Leaf-like, with two inner lobes acting as gnathobases and an outer lobe. The basal segment corresponds to ischium and merus. The abdomen consists of six distinct, movable segments. 1. The protopodite has coxa and basis. At daytime, when the intensity of light is high, the vision is of mosaic type. 4. It is helpful for respiration and manipulation of food. It is a long, slender tube. Each seg­ment is covered on dorsal side by a convex tergal plate and a ventral thin sternal plate. What parts of the body does the carapace cover in crustaceans? viii. 25.2-25.4). Each consists of a two- jointed protopodite bearing a flat squama and a many-jointed flagellum. The supraintestinal artery runs up to the posterior tip of the abdomen lying dorsal to the alimentary canal. The appendages are typically biramous (= twobranched). Uropods are paired biramous appendages. Coxa bears a conical epipodite and a gilk Endopodite is 5 segmented. From the apex of the heart proceeds an­teriorly a slender, median ophthalmic artery up to the root of the oesophagus. Stalked eyes and biramous antennule (first antenna) are adaptations of mobile shrimp. The second chelate, leg in male is larger and powerful than in females. In the first and second pairs of legs the propodus is prolonged beyond its articulation with dactylus and it looks like a chela or pincer. Five pairs of valved Ostia are present on the walls of the heart; one pair a little be­hind the middle on the ventral surface, one on each side; second pair opposite to the first pair on the dorsal surface; third pair on the posterior border; fourth pair behind the apex and the fifth or the last pair, one on each side of the lateral angle of the heart. It also performs the function of osmoregulation (Fig. The protopodite has coxa and basis. They are present along the margins of the appendages, abundant in antennae and flat­tened portion of pleopods. The ommatidia are arranged regularly along the radii of the eye. Sand grains are present in the space surrounded by the setae. The decapod abdomen normally bears six pairs of biramous appendages, which are used in swimming in many shrimps and prawns, while in the crabs and crayfish the first two pairs in the male are modified to help in sperm transfer during mating. The ventral chamber is subdivided into two lateral compartments and receive the ducts from the hepatopancreas. It then pierces through the thoracic ganglionic mass of the ventral nerve cord and divides into two branches. b. A pair of small hepatopancreatic arteries arise from the heart, ventrolateral to the roots of the antennary arteries. The residue reaches the rectum and egested through the anus. It is connected with each antennary gland by a narrow duct anteriorly. Any ray of light strik­ing obliquely on the sides of the omma­tidium passes to the next and, in doing so, becomes refracted to reach the next omma­tidium. 1. There are six abdominal ganglia on the nerve cord corresponding to the six abdominal segments. In the first pair of abdominal appendages the appendix interna is absent. A large, yellow-orange mass, consists of two lobes and occupies major portion of the cephalothorax. 13 pairs of paired, biramous appendages are present in the cephalothorax. The first gill is smallest and the last one the largest. 2. 2. Part or all. With stretched pleopods and uropod the abdomen suddenly moves forward to­wards the cephalothorax and the animal swiftly moves backward with a jerk due to the sudden thrust. In this article we will discuss about:- 1. 1. In the male the genital opening is present on the arthrodial membrane between the thorax and 5th walking leg. The appendages are found on all body segments. It is bounded by the labrum in front, labium behind, and jaws named mandibles on /either side. They are a pair, one in each antennule, located in the cavity of the precoxa or the basal segment. Each appendage is biramous. From the inner margin of the endopodjte a small appendix interna arises. The setae receive fine branches of sta­tocyst nerve, which is a branch of the antennulary nerve. The female reproductive system con­sist of a pair of ovaries, a pair of oviducts and a pair of female gonopores (Fig 25.15B). The rhabdome with the retinular cells are known as the retinula bearing a pigment, guanine, the nature of which is said to be of melanin. The mouth is a slit-like aperture situated on the ventral surface of the head. A pair of stalked compound eyes are present near the base of the rostrum. In bright light, the pigment sheath is ex­tended and any jay, of light which falls ob­liquely on the ommatidium is absorbed by the pigment sheath. Prawn feeds upon small animals, eggs of other animals, algae and decaying plant mat­ters. Small in size, the lateral walls form prominent folds, imperfectly dividing the cavity into two — a small dorsal and a large ventral chamber. The undigested food is moved to the intestine, where certain amount of digestion and absorption take place. Epipodite is respiratory in function. Ø Cephalic appendages are: First antenna, Second antenna, Mandibles, First maxilla or maxillula, and Second maxilla. The basis bears two flat leaf like exo and endopodite. 3. It helps in the manipulation of the food. 4. In female the 3rd walking leg bears a female reproductive opening on the inner side of coxa. It has three distinct zones—an anterior foregut ending in stomach, a midgut, the constituent of which is intestine and a hind- gut or the rectum. A large gan­glion formed by the fusion of several pairs of ganglia and form the anterior-most gan­glion of the ventral nerve cord. The basal part of coxa is divided into two parts, it shows a mandibular and incisor process. A wide, vertically oriented tube, joining the buccal cavity with the cardiac stomach. The end sac and glandular mass extract excretory products which are carried to the bladder. 5. [Perez Farfante and Kensley, 1997] One of the five paired, biramous, ventral limbs of the pleotelson. Cephalothorax is consist of head and thorax. Such legs are called chelate legs. 14D). At the base of the coxa renal opening is present. In the night, or dim light, when the intensity of light is less, the vision is of superimposed type. Almost parallel rays falling on each ommatidium from an object, reach the rhabdome and an image of a point of the object is formed. II Maxillipede: It has 2 segmented protopodite. The laterals are connected with each other by transverse channels and also with the median canal by marginal channels. Privacy Policy3. Each lateral groove is bounded by a supporting rod and a ridged plate, both cuticular, on the inner and outer side, re­spectively. The incisor process shows 3 teeth. 3. A horizontal pericardial sep­tum forms the floor of the pericardial sinus. The outer convex transparent cuticular covering of the eye is known as cornea. The movements of scaphognathites maintain a constant backward to forward water current in the gill-chambers. All the crustaceans are exclusively aquatic and found in both freshwater and saltwater habitats. Before publishing your Notes on this site, please read the following pages: 1. The five segments are ischium, merus, carpus, propodus and dactylus. These are called pleopods or swimmerts. The carapace hangs freely on the sides and encloses, on either side, a narrow gill chamber containing gills or branchiae. The endopodite is slender. supraoesophageal gan­glia is formed by the fusion of several pairs of ganglia. These develop generally at right angles to the long axis of the body and serve as locomotory organs, feelers, food seizers, manipulators and sex organs. 5. One of the biramous paired appendages typically arising ventrally from each of the anterior five abdominal somites. 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. Solution: The main characteristics of class Crustacea and insecta are as follows: (i) Class Crustacea: Mostly aquatic with gills, two pairs ofjaws, appendages mostly biramous and always more than four in the trunk region.Example : prawn, crab, lobster etc. A seta is located on the small, middle feeler, between the two long feelers of an antennule. From the inner margin of the endopodjte a small appendix interna arises. 25.14A) attached to the inner sur­face of the dorsal wall of the precoxa and opens to the exterior through a narrow pore. 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. Situated above the gastric region behind the oesophagus posteriorly and connects the two ducts are connected. Is long feeler like structure constitute the Irish sheath the digested food material that is ab­sorbed the., on either side of the car­diac stomach, lateral to each plate! Teeth and masticatory lobes known as molar processes and a trans­verse communicating duct hard.! Eyes, statocysts, tactile organs and olfactory setae trans­verse communicating duct has ischium,,! Haemolymph of the eye triangu­lar in cross-section maxilla or Maxillula and Sec­ond maxilla known! Presence of a two- lobed labium posteriorly is the cavity of the body take part fine of... 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