biology of shrimp

Biology of shrimp ( P. monodon )

BIOLOGY OF SHRIMP ( Penaeus monodon )

1. Introduction:

P. monodon, the giant tiger prawn or Asian tiger shrimp (and also known by other common names), is a marine crustacean that is widely reared for food. The term shrimp is used to refer to some decapod crustaceans, although the exact animals covered can vary. Used broadly, it may cover any of the groups with elongated bodies and a primarily swimming mode of locomotion. In some fields, however, the term is used more narrowly, and may be restricted to Caridea, to smaller species of either group, or to only the marine species. Under the broader definition, shrimp may be synonymous with prawn, covering stalk-eyed swimming crustaceans with long narrow muscular tails (abdomens), long whiskers (antennae) and slender legs. They swim forwards by paddling with swimmerets on the underside of their abdomens. Crabs and lobsters have strong walking legs, whereas shrimp have thin fragile legs which they use primarily for perching.

Figure: P. monodon

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2. Scientific Classification:

Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostraca Order: Decapoda Suborder: Dendrobranchiata Family: Penaeidae Genus: Penaeus Species: P. monodon

3. Binomial name : Penaeus monodon

4. Other species of Penaeus :

P. carinatus Dana, 1852 P. tahitensis Heller, 1862 P. coeruleus Stebbing, 1905 P. bubulus Kubo, 1949 P. esculentus Haswell, 1879 P. semisulcatus De Haan, 1844

5. Distribution :

Shrimp are widespread and abundant. They can be found feeding near the seafloor on most coasts and estuaries, as well as in rivers and lakes. Its natural distribution is the Indo-Pacific, ranging from the eastern coast of Africa and the Arabian Peninsula, as far as Southeast Asia, the Sea of Japan, and northern Australia. It is an invasive species in the northern waters of the Gulf of Mexico. To escape predators, some species flip off the seafloor and dive into the sediment. They usually live from one to seven years Shrimp are often solitary, though they can form large schools during the spawning season. There are thousands of species, and usually there is a species adapted to any particular habitat. Any small crustacean which resembles a shrimp tends to be called one.

6. The importance of shrimps:

6.1. Shrimp are also very important to the commercial economy. They, too, ar bred and harvested for selling. They are also used as bait for fishing of all sorts. Shrimps are also very important to the environment. Most shrimps have a mutualistic relationship with other fish, in that the fish will provide protection from predators of the shrimp while the shrimp will keep the fish clean.

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6.2. They play important roles in the food chain and are important food sources for larger animals from fish to whales. The muscular tails of shrimp can be delicious to eat, and they are widely caught and farmed for human consumption.

6.3. Causes the shrimp a vital role in the marine environment by cleaning up the bottom in which they live, where he found at autopsy the stomach contents contain organic material decomposing for some animals dead, also plays a vital role in relation to the food chain of marine environments, where there are (the open sea - shallow areas - bays), and has great value in maintaining the balance in the ocean in which they live, and some types of shrimp has the ability to clean and purify water of pollutants nitrogen and phosphorus in addition to pollutants resulting from household waste being dumped in the marine environment.

6.4. The importance of shrimp to the human being lies in the value of food as an essential source of protein, it handled 113 g of shrimp a day provides the human body, including approximately 24 grams of protein and represent 47.4% of the daily needs of the human protein that could be considered a food substitute for meat protein, in addition to that This ratio extends rights to 112 calories and almost less than 1 gram of fat and many people have a misunderstanding about the content of shrimp of cholesterol and fat, Arabian characterized as containing a very small amount of total lipids, in turn contains a high proportion of cholesterol (200 mg in 100 grams of boiled shrimp) As a result, some individuals avoid eating shrimp. Despite this fact, research indicates there is no relationship between intake of shrimp and the level of cholesterol in the blood, tests conducted on two groups of healthy volunteers and enjoy the level of natural fat in the blood.

6.5. The food industry and in particular seafood is especially beneficial to the economy. If countries are shipping shrimp and other sea faring delicacies then it will boost their economy significantly and some of the countries rely on this trade heavily.

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Figure: Shrimp as a frozen food

7. Identification of Shrimp ( P. monodon ):

7.1. Rostrum has 7-8 dorsal teeth and 3-4 ventral teeth and curves down very slightly. Rostral ridge lacks a distinct groove behind it, and the hepatic ridge is long and curved. Telson has a groove but is without lateral apines. Carapace and abdomen have black bands giving a tiger-striped appearance to this species. Pereiopods may be red (Bailey-Brock & Moss, 1992). A thorough knowledge of morphological character is highly essential for the identification of shrimps. These characters are illustrated clearly in the schematic diagram of penaeid shrimp.

7.2. Shrimp can be grouped into penaeid and Non-penaeid. These two groups of shrimps and it can be easily separated. The pleurae on either side of the second abdominal segment overlap the pleurae of the first and third segments in non-penaeids. While in penaeids they overlap only the third segment.

7.3. The first three pairs of peraepods are chelate in penaeids. While in non-penaeids only the first two pairs of peraepods are chelate. For transferring sperms the male penaeids shrimp has petasma and for storing sperms the female has thelycum. In non penaeids such organ are absent. The females of non-penaeid carry eggs in their pleopods as a cluster. While females of Penaeids lay eggs directly in water.

Figure: a. P. monodon b. Petasma c. Thelycum.

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7.4. The major characteristics used in identification of shrimps are mainly the carapace and its spines, the rostrum and its ventral and dorsal teeth, the ridges or carinae, the grooves or sulci, telson, appendages and their segments, petasma and appendix musculina in the male, the thelycum in female.

Figure: P. monodon (Male)

8. Ecology of P. monodon :

In their native range, tiger shrimp mature and breed in tropical marine habitats. Larvae, juveniles and sub-adults occupy shallow coastal estuaries, lagoons, and mangrove areas. Sub-adults subsequently move offshore, where they mature and breed, living on sand or muddy-sand bottom in up to 110 m water depth (Holthuis 1980). Temperature is an important environmental variable that influences not only the success of P. monodon culture, but also the survival and dispersal of wild P. monodon in areas where it is introduced. Survival and growth are optimal at temperatures between 28°C and 33°C, but growth is unlikely below 20°C (Lumare et al. 1993). Lethal extremes are not definitively known, although mortality has been reported at temperatures <13°C and >33°C (Jintoni unpublished). A rapid growth rate and broad tolerance to salinity (2-30‰, FAO 2011) have contributed to the success of this species in aquaculture. However, these are also characteristics that enable it to invade new areas.

9. Habitat & Biology of P. monodon :

Young giant tiger prawns are most commonly found in estuaries, lagoons and mangroves; they are very tolerant to a range of salinity levels from 2-30 ppt. Adults move into deeper waters and live on rocky or muddy bottoms, ranging in depth from 0-110 m (most commonly at 20-50 m). These shrimps may bury themselves in the substrate during the day, emerging to feed at night.

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They live in waters ranging from 28-33°C and are unlikely to survive in waters colder than 13°C. (FAO Fisheries and Aquaculture Department, 2012; Knott, et al., 2011)

Habitat Regions: Temperate; tropical; saltwater or marine. Aquatic Biomes: Benthic; coastal; brackish water. Other Habitat Features: Estuarine; intertidal or littoral.

10. Body Parts of shrimp:

They all belong to the family of Crustacea Decapoda (10 footed crayfish such as river crayfish, lobsters, crabs, shrimps; of lat. crusta, bowl / gr. deca = 10 and pos=foot). The body can be subdivided in two sections (Tagmata), the Cephalothorax (the piece of head and chest) in the front, and in the back the abdomen.

10.1. Cephalothorax:

Two complex eyes protrude at the sides of the carapax (synonymous: facette eyes, often also called shaft eyes), the head carries 2 pairs of antennae. At the basis of the second pair of antennae there is a scale-like exopodite, the scaphocerite.There are a pair of maxillae (for chewing or scrunching of food or as gripping tool in the case of transport and/or manipulation of objects) and two pairs of maxillipeds (foot jaws) that have pincers; the first pair in particular can be quite large e.g. for Macrobrachium.The other thoracic extremities form the peraeopods (of gr. peraioo = transport over there). The basic parts of the peraeopods carry the gills.

10.2. Abdomen:

The abdomen consists of the abdominal segments and the tail fan. The abdominal segments, contrary to those in the thoracical region, have not merged and thus form a mobile floating body. This "flexible" structure helps the maneuverability when swimming. The abdominal extremities, the pleopods, serve as swimming feet and, when the shrimp is walking, are folded under the abdomen. The last pair, the uropods, form the tail fan together with the telson.

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Figure: Body parts of shrimp.

11. Morphology of a shrimp:

Shrimp morphology can be divided into two parts. Such as:

External morphology & Internal morphology

Brief description about the morphology of a shrimp given below:

11.1. External features of a shrimp:

Shrimp are a vital yet very small part of the underwater world that makes up over 70% of the earth. They are a small number of invertebrates in nature, both marine and freshwater, but make up a huge portion of the invertebrate population of aquarium hobbyist. They are used as eye catchers, accents, and mostly as clean-up crews. They are magnificent little creatures and today we will discuss their anatomy.

The shrimp has nineteen (19) separate sections of the body. Two (2) main segments make up the body of a freshwater or marine shrimp. The first part is the upper portion of the shrimp, referred to as the cephalothorax. The cephalothorax includes the head and the thorax or pereon region of the shrimp. It is covered by a protective plating system called the carapace. Shown below is the cephalothorax noted with body parts.

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Figure: External part of shrimp.

The cephalothorax consists of the rostrum (nose), stalked eyes, carapace, the 1st and 2nd antennas, antenulles, pereopods (walking legs – 5 sets), the maxillipeds, and the mandibles (jaws). The antenna and antenulles are used as feelers or sensory feelers. The maxillipeds are used to rip food apart before it is moved into the mandible where it is crushed and devoured.

Below is a picture of the lower portion of the body, often called the abdomen or pleon segment. This include both abdominal section upper and lower. The upper abdominal section, 1-3, is referred to as the tergum. The bottom half, 4-6, is referred to as the pleuron. The pleopods, often called swimmerets, are tucked under the abdomen of the shrimp. It also includes the tail section of the shrimp that is broken into three parts. Two of which are called uropods, and the central pointier segment is the telson. The pleopods are used for swimming while their tails are used like aircraft wings to control their direction.

Figure: External part of shrimp.

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Hopefully this helps you to be able to better see the separation and parts of the shrimp that we keep. Below in a picture, it shows a great split in the tail portions and what we should use to identify the difference between the telson and the uropods.

Figure: Telson & Uropod of Shrimp.

Here is another picture by Fishalicious showing the carapace and separation of the 6 abdominal sections.

Figure: View of external body parts of a shrimp.

11.2. Internal anatomy of a shrimp :

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Internal organs that can be observed are the gut (intestine), which leads to the anus located at the end of the sixth segment.

i. Tiger shrimp are carnivorous animals that feed on small crustaceans, amphypoda, and Polychaeta. Tiger shrimp are naturally nocturnal animals are active at night to find food, whereas during the day hiding in the substrate or mud. But in pond aquaculture feeding can be done more frequently to spur growth.

ii. Tiger shrimp need food with protein content around 35% lower when compared with shrimp that require feed with protein content of 45%. Shrimp growth is influenced by two main factors that molting frequency and growth rate increases. Environmental conditions and food are the main factors that affect molting.

iii. During the molting process, there has been solving the cuticle between the carapace with intercalary celeryte, whereas in the anterior part of cephalothorax and appendages are interested to stretch. The newly formed carapace after moulting is very soft and getting more and more hardened to adjust the size of the shrimp body.

iv. Moulting frequency on tiger shrimp decreased along with increasing the size of shrimp. The larval stage, the tiger shrimp molting every 40 hours at 280C. While juveniles weighing 1-5 grams, molting every 4-6 days. The next on the weight of 15 grams, the period of moulting occurs every 2 weeks.

Figure: Internal anatomy of a shrimp.

12. Difference Between Shrimp and Prawn:

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The primary difference is the gill structure. Shrimp have branching gills, while prawns have lamellar gills with a plate like structure. There are a few other distinguishing features. The front pincers of shrimp are typically the largest, while prawns have bigger second pincers. Prawns also have longer legs. These differences may seem subtle, but they indicate different steps along the evolutionary path of both creatures.

Numerous varieties of both creatures are harvested for consumption. Some common shrimp species include spot, pink, white, and brown shrimp, along with Northern shrimp. Prawns that may be found at the fishmonger include tiger, deep water, bay, and king prawns.

Conservation organizations urge consumers to use caution when purchasing prawns and shrimp, since many are caught and farmed in nations with lax environmental and fishing regulations. The United States in particular has made major changes in the legislation governing shrimp farming, in the hopes of making it more sustainable, so that farmed in America is a reasonable choice at the grocery store. Wild-caught Northern shrimp are also good buys, as are spot prawns.

12.1. Taxonomy of a Shrimp and a Prawn:

Shrimp is a crustacean that belongs to the order Decapoda and the suborder Pleocyemata. Prawn is a crustacean that belongs to the order Decapoda and the suborder Dendrobranchiata.

12.2. Morphology of Shrimp and Prawns: Shrimp have a thin but hard exoskeleton. Their bodies are divided into three segments: head, thorax, and abdomen. The thorax overlaps the other two body segments. Prawns have the same exoskeleton and body segmentation as shrimp. However, in prawns, the head overlaps the thorax, and the thorax overlaps the abdomen.

Figure: Segmentation of Prawn & Shrimp.

13. The Life Cycle of a Shrimp:

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Figure: Life cycle of shrimp.

13.1. Shrimp egg:

Shrimp eggs are tiny, almost invisible particles released deep in Gulf waters to float in the water column, providing food for zooplankton and incidental nutrition primarily for filter feeders ranging from rays and sharks to mollusks. Released in certain salinities when water temperature increases significantly, these tiny eggs fill a niche that is lagniappe for most animals that consume them and a selected food source for a few small fishes at the bottom of the sea’s food web. Although shrimp mature from eggs to larvae in a short time, shrimp eggs are available to the food web over a long period because spawning is not an isolated event. White shrimp spawn two or three times when stimulated by temperature increases from late spring to early fall (from April to September off Louisiana). Brown shrimp spawn throughout the year, although April to May and September through November appear to be peak spawning times off Louisiana’s coast.

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Figure: Shrimp egg.

13.2. Nauplius Larva and Protozoea Larva:

Larvae develop from floating fertilized eggs, growing and molting through many of each of these stages over a two- or three-week period. Although shrimp at all life stages are opportunistic omnivores (consume both plants and animal matter), these hardly visible nauplii and protozoea have little control over their diet. They cannot swim or control their movements. Nevertheless, they interact with other species as feeders and as food throughout the water column. They feed on nanoplankton, zooplankton and phytoplankton (green algae, copepods and diatoms) as well as suspended detritus, while small fishes and filter feeders consume some of them.

a) Nauplius Ib) Nauplius IIc) Nauplius IIId) Nauplius IVe) Nauplius Vf) Nauplius VI

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Figure: Different stages of nauplius.

a) Protozoea 1b) Protozoea 2c) Protozoea 3

Figure: Protozoan larvae.

13.3. Mysis Larva:

Maturing larvae in the mysis stage are carried towards shore by flood tides and wind-driven currents, continuing to feed on zooplankton and phytoplankton. A shrimp larva at this life stage is large enough in size for some juvenile fish to see and hunt. Its niche is more noticeable and it is more aware of its environment. Mysis larvae seem to respond to light by moving away from it — that is down in the water column to avoid predators – although they do not yet have swimming appendages.

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In figure:

a) Mysis 1b) Mysis 2c) Mysis 3d) Postlarvae 1

Figure: Mysis and post larval stages.

13.4. Post larva:

Currents and incoming tides carry the maturing crustacean into brackish (mixture of salt and fresh water) estuarine waters. Over a 4-6 week period, the individuals begin to look like shrimp and to forage or graze like shrimp, clinging to the bottom most of the time. They develop swimming and walking legs.

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Figure: Stages of growing post larvae.

13.5. Juveniles:

Over the next one or two months, the juvenile shrimp interact with many species as predator and prey throughout the estuary as far inland as covered by salty waters, and outside along protected coastal areas. Small juveniles prefer shallow salty water along the edges of marshes, where plants provide both cover and detritus, and where microorganisms thrive in the soft bottom. Small juvenile shrimp are food for juvenile fishes also living in the estuary such as southern

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flounder, spotted sea trout, red drum, inshore lizard fish, Atlantic croaker and pinfish.. As they graze on the soft estuary floor, juvenile shrimp contribute to turbidity, thus stimulating bacterial and micro-algal growth, which, in turn, increases their own food source. They consume whatever is available such as detritus, chitin, parts of worms and snails, fish parts, sponges, corals, copepods, other crustaceans, algae and vascular plant stems and roots. Cannibalism is common. As maturing juvenile shrimp move farther into the estuary to satisfy their appetites, their effect on the estuary spreads.

13.6. Sub adult:

Temperature changes stimulate growth, and, along with salinity changes, regulate the maturing shrimp’s migration within the estuary and back out to sea. The subadult scavenges for detritus, chitin, parts of worms and snails, fish parts, sponges, corals, algae, and vascular plant stems and roots, as well as other juvenile shrimp. It is an important food source for many predators of increasing size – pinfish, sheep shead, red drum, black drum, Atlantic croaker, sand sea trout, sea catfish, gafftopsail catfish, southern kingfisher, southern flounder and spotted seat rout. It is also popular with commercial fishers seeking bait.

Figure: Sub adult of P. monodon

13.7. Adult:

Out in the Gulf once more, the adult shrimp continues to grow in size on the sea’s bottom as an opportunistic omnivore, and its niche at this stage is primarily as food for many. It lives in deep water, 60-500 feet below the sea’s surface. The adult shrimp, around a year old, will be snared by commercial trawlers and consumed by spotted seatrout, lady fish, crevalle jack, bluefish, However a few will survive long enough to reproduce when a sharp increase in the water column’s temperature will stimulate the females to spawn, producing thousands of eggs to begin the cycle again.

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Figure: Life cycle of P. monodon

14. Reproduction :

Mating can only occur after the female has shed her exoskeleton and while her skin is still soft. The female carries the fertilised eggs (which number in the thousands) under her body between the swimmerets. This not only protects the eggs but the pulsing swimmerets, keeps them aerated. After hatching the larvae are carried by the currents and join other plankton.

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Figure: Reproduction of P. monodon

15. Mating of P. monodon :

Mating success of the pond-reared shrimp was found to be low relative to wild-caught shrimp. It was determined that both male and female shrimp contributed to this low mating rate suggesting both genders were impacted negatively by the domestication process. The causative factors for the low mating success are yet to be determined; however, external physical abnormalities and lack of sexual maturity did not appear to play a role. The most notable behavioral difference between wild-caught and domesticated shrimp was a reduced level of pursuit behavior by domesticated males. This, and other behavioral differences are discussed in relation to an increasing body of evidence that male prawns respond to sex pheromones produced by receptive females and that males detect these chemical signals in part via their second antennal flagella. Accordingly we hypothesize that pond-reared females may have a reduced ability to produce or release sex pheromones and males, a reduced ability to detect them when compared to their wild-caught counterparts.

Mating between a male and female shrimp happens extremely fast. In a matter of seconds the male latches onto the female abdomen to abdomen, deposits his sperm, and quickly then releases the female. Eggs develop in the female prior to spawning, and can be seen as a dark band just under the shell on the head. Shortly after mating, eggs are extruded to the underside of the abdomen, where they are fertilized by a packet of sperm previously obtained from the male, then attached to the female's specialized legs. The female carries the developing eggs until they hatch in early spring. Newly hatched shrimp larvae are small (about 3/16 of an inch, or 5mm), planktonic (free floating, unable to swim against currents), and bear only a superficial resemblance to adults.

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Figure: Mating of P. monodon

16. Fertilization :

Shrimp have to shed their shells in order to grow bigger, a healthy shrimp in good water conditions will usually molt at least once a month (more if it is young and still growing like crazy). After they shed the old shell, it takes a few days for their new shell to harden up again and it is during this vulnerable time that the male shrimp "give" the female a packet of sperm--you'll often see the males chasing around the female at this time (she puts out some scent they can sense), She takes it into her body and her mature eggs will be fertilized with the sperm as they pass down her (ofr lack of a better name) "birth canal" on their way out of her body. The male deposits the sperm into the female before the eggs are passed from the ovaries and into the undercarriage. As the eggs are passed down into the undercarriage they become fertilized by the previously deposited sperm. There is a big misconception that the eggs are fertilized after they appear in the undercarriage which is untrue. It is believed that the male has a tiny "appendage" that it uses to deposit the sperm into the female. She tucks each egg under the tail and carries them around in clusters (they look like wee tiny grapes). Her swimmeret legs fan the eggs to oxygenate them and to keep the fungus off of them. She will occasionally rearrange them when she feels it is necessary. She'll carry them around for about 3-4 weeks while they mature. When they are fully mature, she'll find a safe place to stand and fan the eggs as the babies hatch, sending them into the water. They will be in a larvae stage (they look kind of like mosquito larvae and are quite defenseless, can hardly mobilize themselves) and just sort of float around eating what they can grab with their arms. Even the adult ghost shrimp will eat them if they catch them. If they are lucky enough not to be eaten or to die from lack of food or polluted water, they will molt after a few days and molt again as they grow. After about 2 weeks they will have molted into little small shrimp shapes and will go scooting off into the underbrush to hide and eat until they are big enough not to look like food to everyone.

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17. Hatching :

The actual hatching of the shrimp is extremely fast. The baby shrimp seems to pop out of the egg in under a second and latches onto the first thing it can find, typically a plant like moss. People that have observed the actual hatching say that the baby shrimp seem to fly out of the belly of the female. Female seems to assist the babies out by "kicking" them or giving them a nudge. It is very rare to observe the actual hatching of a shrimp. The females tend to hide and the hatching may even occur at night.

18. Molting: Molting process is given below:

18.1. Postmolt (postecdysis):

Postmolt is the stage just following exuviation (shedding of the old exoskeleton). It is the period when the exoskeleton expands due to increased hemolymph volume from water influx. Water influx occurs across the epidermis, gills, and gut. After several hours or days (depending upon total length of the molt cycle), the new exoskeleton hardens and retains its rigidity (Chang, 1992). Immediately after ecdysis, the only layers present are the epicuticle and exocuticle. Within a few hours the epidermis starts to secrete the endocuticle. Most of the cuticle must be derived from materials stored in the epidermis, as feeding does not begin until the prawn is well into the intermolt stage. This secretion continues until the prawns are in the intermoult condition, when the three layers are fully formed (Dall et al., 1990).

Figure: Postmolt

18.2. Intermoult:

During intermolt the exoskeleton becomes much harder through mineral and protein deposition. Shrimp exoskeleton is relatively thin and soft compared to crabs and lobsters (Chang, 1992). The volume as well as the weight of the whole prawn increases by 3-4% during the intermoult period. This increase may be due to extension of the thin intersegmental connections of the abdomen, and supports the concept that growth in penaeids is a more continuous process than in the heavily armoured decapods, which moult relatively infrequently (Dall et al., 1990).

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Figure: Intermoult

18.3. Premolt (proecdysis):

Premolt (proecdysis) stage occurs just prior to exuviation, and is characterized by separation of the old exoskeleton from the underlying epidermal layer. The old exoskeleton is partly reabsorbed, and energy reserves are mobilized from the midgut gland. Premolt begins with an increase in concentration of molting hormone in the hemolymph (Chang, 1992).

The first indication that the prawn is entering proecdysis is the withdrawal of the epidermis from the old cuticle (apolysis). Later the epidermis starts to hypertrophy and cells, which appear to have a storage function, accumulate in it. As the prawn proceeds through this stage, the epidermis starts to secrete a new epicuticle and exocuticle.

Feeding starts to decline and has completely ceased by the end of the proecdysis. Thus reserves need to be available for cuticle synthesis and for the period when feeding ceases. The material for cuticle synthesis are derived from two sources: accumulated reserves due to feeding and resorption from the old cuticle (Dall et al., 1990).

Figure: Premoult

18.4. Ecdysis:

Ecdysis, as a stage, only lasts a few minutes. It begins with the old exoskeleton opening at the dorsal junction of the thorax and abdomen in decapod crustaceans, and is completed when the animal escapes from its confines (Chang, 1992).

Since uptake of water determines the size until the next moult, this is the most important single physiological process at the end of the proecdysis and during ecdysis. Other decapods absorb

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most of their water by drinking, but this process has not been investigated for Penaeidae. Presumably there is some uptake in the late proecdysis, but it appears that water uptake must be limited to a few hours on either side of ecdysis, as the cephalothorax swells only immediately before ecdysis, and the cuticle hardens appreciably within a few hours afterwards (Dall et al., 1990).

Figure: Ecdysis

19. How to tell a P. monodon healthy :

Characteristics of a healthy P. monodon are given below-

i. Eyes should be normal, bright.ii. Gills are transparent clear, not swollen.

iii. Hepatopancrease are soft, brown to raddish.iv. Segmentation is clear and with no cracks, blackening.v. Shell is firm and smooth, clear with slight green color but not blue nor dark nor

raddish.vi. No black spot nor damage on the shell.

vii. Rough shell. If present, always begins from telson.viii. Telson is open, uncut and undamaged.

ix. Abdomen is clean and clear.x. Swimming/ Walking legs (10 pairs) are complete, clean, uncut and with

pigmentation.xi. Antenna’s length is longer than body’s and not broken nor easily broken.

xii. Antenna peduncles are complete with no lesion or big blisters.

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Figure: Healthy P. monodon

20. Food & feeding habit of P. monodon :

Preliminary studies on the food and feeding habits of Penaeus monodon from Korapuzha estuary were undertaken. The food of the species consisted of crustaceans, fishes, molluscs, polychaetes and vegetable matter in order of importance. Mud and sand particles were also found among the food items. There was no appreciable variation in the nature of the food in the different size groups the food of P. monodon consisted of crustaceans, molluscs, polychaetes. Fishes and vegetable matter in the order of abundance. Crustaceans formed nearly 50% by volume of the stomach contents in all months except July. Shrimp are found primarily on or near the bottom, but make daily migrations through the water column in search of food. They have been found at depths greater than 1,000 feet, but are most frequently captured at depths of 30 to 300 feet.

Adult shrimp are omnivorous, feeding on marine worms, small crustaceans, large planktonic organisms, sponges, and dead animal and plant material.

21. Conclusion :

Shrimp are very important to the commercial economy. They are bred and harvested for selling. They are also used as bait for fishing of all sorts. Shrimps are also very important to the environment. Most shrimps have a mutualistic relationship with other fish, in that the fish will provide protection from predators of the shrimp while the shrimp will keep the fish clean. Shrimp are sold directly to processing plants, specialized teams for harvesting and handling are commonly used to maintain shrimp quality. After sorting, shrimp are washed, weighed and immediately killed in iced water at 0–4 °C. Often sodium bi-sulphate is added to the chilled water to prevent melanosis and red-head. Shrimp are then kept in ice in insulated containers and transported by truck either to processing plants or domestic shrimp markets. In processing plants,

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shrimp are placed in iced bins and cleaned and sorted according to standard export sizes. Shrimp are processed, quickly frozen at -10 °C and stored at -20 °C for export by ship or air cargo. Due to an increasing demand, no taxes and higher profit margins, many processing plants operate value-added product lines.

Reference:

1. BALSS, H., 1933. Ueber einige marine Penaeidea (Crustacea Decapoda) des Malaiischen Archipels. Treubia, vol. 14, pp. 227—236, figs. 1—5.

2. MAN, J. G. DE, 1911. Family Penaeidae. The Decapoda of the Siboga Expedition. Part I. Siboga Exped., mon. 39a, pp. 1—131.

3. ALC0CK, A. 1906. The Prawns of the Peneus Group. Catalogue of the Indian Decapod Crustacea in the Collection of the Indian Museum. Part III. Macrura. Fasciculus I, pp. i, ii, 1—55, pis. 1—9.

4. SCHMITT, W. L., 1926. Report on the Crustacea Macrura (Families Peneidae, Campylonotidae and Pandalidae) Obtained by the F.I.S. "Endeavour" in Australian Seas. With notes on the species of "Penaeus" described by Haswell and contained, in part, in the collections of the Macleay Museum, at the University of Sydney. Biol. Res. "Endeavour" 1909—'14, vol. 5, pp. 307—381, pis. 57—68, 1 map.

5. GEORGE, M J., 1970. Syno psis of biological data on penaeid prawn Metapcnaeus dobson; (Miers). 1878. FAO Fish. Rep .. (57), Vol. 4, 1335- 1357.

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