• Zoothamniosis disease is one of the parasitic diseases found in vannamei shrimp caused by Zoothamnium penaei which usually lives with poor water quality. It causes the death of shrimps both in pond and hatchery. An abundance of Zoothamnium sp. infested the vannamei shrimp this is still reasonable so long as they do not cause high mortality. But, they can also cause problems in shrimp culture when the environmental conditions are poor and suitable for its development. This parasite that attack shrimps in order to determine the factors causing a decline in growth, meat quality and productivity.
• This disease causes the shrimp to breathe hard, difficult to move and cannot find food, difficult to moult, inhibit growth, reduced economic value and cause death to 91%. In addition, this disease is a predisposing factor of secondary infection by bacteria and viruses.
• Protozoan ectoparasite abundance varies greatly depending on the different physico-chemical conditions of the water bodies. Parasitic groups of protozoans are generally found in environmental conditions that experience instability in the water quality, especially temperature, as Zoothamnium sp. can breed faster in environmental conditions that have a temperature value above 30°C. Giving too much food causes the remaining food to be left in many ponds. This means that the content of the organic matter in the pond is high and spurs on the growth of the parasites which are also able to grow well.

Symptoms

Zoothamnium sp. Infected shrimps show black/ brown gills or appendage discoloration or fuzzy/cottony appearance due to a heavy colony of the organisms. In some cases, the severely affected shrimp die during the molting period.

The base of Zoothamnium forms a circular disc that fuses with the epicuticle but does not penetrate the underlying cuticle or epithelium. Discoloration of the gills is a common symptom of fouling by organisms and also detritus, silt, or iron which are trapped by the fouling organisms. 

Treatment

Chlorine and formalin are often used to treat those commensal organisms if shrimp display heavy infection. Changing water is the most preferable management, which stimulates molting of the shrimp in order to reduce the infestation.

Prevention and Control

Prevention and control of the occurrence of surface fouling are usually done through maintenance of good sanitary conditions at the pond bottom and the overall pond area. Organic matters and suspended solids in the pond should be reduced to prevent the attachment of those fouling organisms. This is achieved by changing the water or applying lime.

Why Bacteriophages?

With emergence of highly virulent pathogens in animal health and aquaculture, there is need for highly effective therapeutic product which can reduce usage of sanitisers and antimicrobials. Continuous use of sanitisers and antimicrobials lead to damage of microbiome (the normal non-pathogenic beneficial bacteria) in aquaculture pond ecosystem and shrimp gut. Recent explosion of scientific research has brought to light the importance of maintaining good and unfluctuating microbiome in shrimp and fish health and aquaculture success.

Under this condition Bacteriophages against virulent pathogens in aquaculture will be highly helpful in maintaining the natural ecosystem of the pond while killing the aquaculture pathogens. This strong argument inspired Salem Microbes to initiate Bacteriophage research as early as 2018 and has invested in infrastructure, technology, and technical competence in bacteriophages-based solution development for Aquaculture, Poultry and Food safety.

Salem Microbes possessing 23 years of probiotic tradition has always travelled with Bacteriophages hand in hand from screening to production operations. In the current day scenario, we are ‘embracing the foe as a friend’ to control pathogens of aquaculture. So, we are just jumping sides and exploiting their potential.

Today, we assure that we are in the forefront of bacteriophage research, specialising in isolation, characterisation, and formulation of Phage cocktail within a short turnaround time. Our Research & Development ensures quick screening in case of a sudden disease outbreak to make custom formulation of Bacteriophages from our expansive library of Bacteriophages maintained on-campus.

Phages and Probiotics , a Synergistic combination

Probiotics have played an undeniable role in the environmental management of the shrimp pond and are going to continue to sustain the shrimp ecosystem microbiome, the only catch here is use of quality probiotic inputs which farm owners and technical experts should be aware of.

Probiotics reduce the chances of infection by Competitive Exclusion, but once the critical levels of Vibrio species dominate the environment, it become nearly impossible for probiotic bacteria to exclude Vibrio species. Such critical condition demands quick and sure shot treatment, which is non residual in nature and non-GMO and which does not affect the (microbiome). Here comes the concept of Phage Therapy which is highly specific and quick acting in nature specifically targeting the aquaculture pathogens.

How a Bacteriophage product become relevant to a condition?

A Good Bacteriophage consortia should contains identified lytic phages, specific against pathogens selected from the target environment. Phage cocktails against Pathogens should be continuously upgraded to maintain the pathogen spectrum, specificity and infectivity.

How does a Phage works?

Bacteriophages are Viruses of bacteria which enter the bacteria, use the bacterial source of energy, hijack the bacteria, multiply inside the bacteria and kill them by lysis. When they kill the bacteria, each virus which enter the bacteria multiplies and releases 10 to 100 mature ready-to-attack bacteriophages which are capable of infecting and destroying next set of target pathogenic bacteria.

V PHAGES Consortia

V PHAGES Cocktails for Hatchery and Growout are quite different in their Formulation, Specificity and Purpose. V PHAGES HATCHERY satisfy the need for targeting pathogens specific and prevalent in Hatchery water source, live feeds and also its environment. V PHAGES GROWOUT targets the common pathogens esp Vibrios which are the main cause for bringing down the productivity of a shrimp pond by causing Vibriosis leading to White gut, White faecal disease, off feed, Running Mortality Syndrome and crop loss.

"V PHAGES " cocktails target Vibrio species as,

• Vibrio parahaemolyticus
• Vibrio alginolyticus
• Vibrio harveyi
• Vibrio campbellii and other pathogenic Vibrio sp.

When TO USE IN SHRIMP HATCHERIES?

• To reduce the load Vibrio sp. of the live/ wet/ frozen feed used in brood stocks.
• To reduce Vibrio sp. load in artemia tank.
• To reduce the Vibrio sp. associated problems in Conversion and PL tanks.
• To reduce Vibrio sp. load in intake water thereby preventing biofilm formation in the storage tanks and pipe line downstream of the intake tank.

When TO USE IN SHRIMP GROWOUT PONDS

• Drop in feed intake with increase in yellow or green colonies in TCBS plates
• White gut and White faecal matter appearance coupled with more green colonies in TCBS plates
• Early stages of Running mortality syndrome with empty gut symptom.
• During stocking to safeguard against survival loss of PL’s.
• To increase the efficacy of Probiotics by reducing their primary enemies, the pathogenic

Comparing with Other Therapies

V PHAGES are Natural isolates screened and selected for their strong and fast action against their challenged targets. They do not disturb the Probiotics and other non-pathogenic natural microbiome which are otherwise destroyed by other treatment approaches as Sanitisers, Disinfectants and any products of anti-microbial action. These Phages does not leave any residues on the shrimp or environment as they are Natural. All  bacteriophages in V PHAGES cocktail are Genotypically characterized to ensure proprietary formulation and traceability, which makes them special.

Conclusion

Though Bacteriophage research and applications are known for many years very few products have seen the light of the day. Even these products become irrelevant when they are not supported by a strong expertise in the field and research infrastructure. Salem Microbes has established these capabilities and commits to be in the forefront of giving the Best to its farmers to make their Shrimps Healthy, Productive and Profitable.

• Water Quality plays an important role in the productivity of shrimp culture. Maintaining the water transparency at desirable levels (25-35 cm) is crucial to enhance the survival and growth of shrimp. Transparency refers to the penetration of light through water, which indicates the concentration of suspended solids.
• Suspended solids which make water turbid in shrimp culture systems include plankton blooms, flocculated organic matter, chemical precipitates, and sediment stirred up from the bottom of the pond.  
• Turbidity due to both plankon density and suspended silt and clay particles can be measured in terms of transparency using Secchi disc. This tool is used to monitor the density of phytoplankton population. Presence of plankton blooms affect the sediment quality leading to release of toxic gases like ammonia in to the pond water. 
• A secchi disk is a black and white disk that is lowered into the water until it can no longer be seen; that depth (secchi depth) is then recorded as a measure of the transparency of the water (inversely related to turbidity).
• There is a high correlation between secchi disc visibility and phytoplankton (water colour) density.
• Secchi disc visibility is the average of the depth at which a disc, a round plate with alternating black and white quadrants disappears and reappears from view when sunlight is intense or moderate. The optimum range for secchi disc reading is between 30 and 60 cm to the juvenile stage and between 25 and 40 cm to the sub-adult and final stage.
• High value of transparency (>60 cm) is indicative of poor plankton density and therefore water should be fertilized with right kind of fertilisers.
• Low value of transparency indicates high density of plankton and hence fertilization rate and frequency should be reduced.
• High secchi disc reading is associated with low productivity of the pond and low secchi disc reading is associated with high productivity of the pond.
• In general, high productivity ponds are having high biomass that increases oxygen consumption, which may lead to oxygen depletion.
• The optimum range of transparency is 25-35 cm.
• Transparency less than 20 indicates that the water is unsuitable for shrimp culture and should be changed immediately to flush out excess bloom.

Secchi Disc Measurement

• Secchi disc is a simple circular plate/disc with alternate segments painted black and white.
• The plate/disc is mounted at the end of a rod/stick upon which distances are marked with zero being at the plate end.
• To take transparency measurements a farmer can either stand on walkway platform or at the edge of the dike and lower the secchi disc holding the end of the stick slowly into the water.
• The depth at which the black and white segments of the disc disappear is the secchi disc reading.

Application of zeolites and water exchange are routine practices in shrimp culture to control the turbidity.

• Biofloc is a clumpy assemblage of microorganisms (bacteria, microalgae, cyanobacteria, fungi, protozoans, micro-zooplanktons, etc.) with dead particulate organic matter suspended in the water column of an intensively aerated or agitated aquaculture system.
• Exopolysaccharides secreted by bacteria, and certain kind of microalgal species helps in the formation of biofloc. These biopolymers act as adhesives to aggregate the dispersed cells of bacteria, microalgae and other particulate organic matter to form a clumpy mass called bioflocs.
• The Indian vannamei shrimp farming industry has been greatly affected by many disease outbreaks wherein in many cases cultures are lost in a matter of 15 days. This causes huge economic loss as a considerable investment is made in preparation of large grow out ponds. To overcome this, onsite nursery rearing of shrimps from its early postlarvae up to an average size of 1 to 2 g is highly recommended and is an emerging trend.
• Nursery ponds in comparison to grow-out ponds are smaller and can be easily managed for operations faster and at a lower cost even in the case of a disease outbreak.
• In biofloc based nursery rearing, these consortia of bacteria and microalgae clean the unwanted nutrients such as ammonia, nitrite, nitrate, sulphide, etc., which are otherwise toxic to the shrimps by utilising them as a source of nutrient and energy in their metabolic pathway.
• In addition to this cleaning process, biofloc themselves act as a fresh feed (in situ feeding) within the system. This is considered to be a low-cost, sustainable feeding tactic and is receiving popularity in farming of white leg shrimp around the world. Biofloc is found to be a nutritionally rich and balanced with a good amount of protein, minerals and other micronutrients.
• Bioflocs not only act as a feed but also manages the water quality with no any additional cost.
• Nursery rearing of shrimp post larvae (PL) in this biofloc based tanks, ponds or raceways before stocking in the grow-out pond has been observed to increase production by 20 – 30 % and lower the cost of production.
• The PL obtained from the hatchery are reared for a period varying from 20 – 45 days until the PL reaches PL 45 or early juvenile stage of size ranging from 0.3 g to 1.2 g. Stocking of large sized post larvae has been observed to reduce growout period from 20 – 30 days and improve the FCR by 10 – 30 %.
• Stocking larger PL which has been acclimated to the pond conditions has been a strategy to mitigate the issue of diseases like early mortality syndrome (EMS) and white spot syndrome virus (WSSV) infections to some extent.
• As the biofloc based nursery rearing system is preferred over the conventional nursery as it is a zero or minimal water exchange based system.
• The biofloc based nursery rearing technology is based on the adjustment of the C: N ratio in a bacteria-based system.
• The addition of carbon-rich sources in well-aerated ponds stimulates the growth of heterotrophic bacteria which in turn make use of inorganic nitrogen in the form of ammonia and nitrite for generating bacterial protein and thereby create a self-nitrifying system with protein rich flax forming an additional feed to shrimp.
• Postlarvae (PL3) reared in biofloc (107 CFU/ml) based rearing system showed significantly higher growth and survival than in conventional non-biofloc system.

• DO is the most important and critical water quality parameter because of its direct effect on the feed consumption and metabolism of shrimp as well as indirect influence on the water quality.
• Maintenance of adequate level of dissolved oxygen in pond water is very important to shrimp growth and survival. 
• DO can be affected by many factors particularly water temperature, respiration of plants and animals and the level of organic matter.
• DO should be maintained in the range of 3-10 mg/l. For penaeid shrimp, optimum concentration of DO for maximum growth rate is 6 ppm.
• Prolonged exposure to low oxygen content causes low feed consumption which leads to slow growth, anoxia and the culture organisms become inactive and they are susceptible to disease. 
• DO in the waters come from two sources: 
  • As a by-product of photosynthesis and
  • Diffusion of atmospheric air.

Low level of oxygen concentration can be caused by a number of reasons 

• Dissolved oxygen decreases when temperature and salinity decrease.
• Oxygen concentration decreases depending on the depth of water.
• Dissolved oxygen normally decreases during night time. During the day, algae and plankton photosynthesize (with sunlight) and create oxygen dissolved in water. Absence of sunlight at night prohibits photosynthesis activities. At night, on days without sunlight or with overcast weather and rain, water will not have enough dissolved oxygen for shrimps.

Some symptoms of shrimp when water with dissolved oxygen is lacked:

Shrimp concentrates near water surface, edges of ponds, near position where water comes in; lethargic shrimp with strong respiratory rate, coma and possible death in shrimp.

Effects of DO in shrimps:

How to overcome the lack of DO in the pond?

• Increase the number of aerators. Normally dissolved oxygen is increased by using paddlewheel aerator or aeration blower. The use of aerators result in mixing of water at surface and bottom and breakdowns DO stratification and also can eliminate black mud formed at interface of pond water and bottom mud.
• Carryout water exchange to flush out the settled sediments/ pond waste and oxygen depleted water. Flow through water exchange can also be done.
• Over feeding should be avoided in order to maintain the DO level. One of the effects of overfeeding is to decrease the feed conversion efficiency.
• Application of DO enhancers can be undertaken to increase the DO level in the pond water as well as to oxidation of organic matter settled on the pond bottom due to the plankton crash. While Hydrogen peroxide, Pottasium permanganate provides an immediate burst of oxygen in the pond. Several commercial products containing compounds such as Calcium peroxide and Sodium perporate/ per carbonate are effective oxygen enhancers to overcome the sudden drop in DO of the pond. 

• Nursery systems for vannamei culture across the world are reaching new heights with high density stocking and very intensive farming systems with zero water exchange in order to keep all parameters constant. Prerequisites are highly efficient filtration systems similar to those used in hatcheries.
• Shrimp juveniles reared through nurseries before stocking into growout ponds are healthier and stronger, grow faster and typically have better FCR and survival rates, as well as significant potential for compensatory growth.
• In a nursery system there is better control of water quality and shrimp health.
• Shrimp nursery systems are valuable production tools and a significant opportunity for the shrimp farming industry to increase efficiency and profits, and in some cases to help manage some diseases.
• In the nursery system, the animals could be monitored better as it was a smaller area of operation. It could check the occurrence of disease right to start when the infection sets in. If he nursery animals are found to be infected by diseases, the stock could be discarded and a fresh batch could be quickly started, without jeopardizing the entire farm. This way the entire farm will not have to be cleared and disinfected. It saved a lot of time and energy and is economically a better option.
• In all, managing one nursery area for about a month is a lot more economical than managing the same stock spread out over a huge area.
• Properly designed and implemented, they are high-biosecurity facilities to grow post larvae (PL) at high densities, from about 2 mg to sizes as large as 3 grams, resulting in healthy, strong and uniform juveniles with significant potential for compensatory growth after their transfer for final grow-out to market size.
• In general, nurseries typically use plastic-lined tanks or raceways covered by plastic greenhouses or roofs suspended by cables, with an area of 300-7500 m². Systems can be square or round (typically with circular flow around a central drain) or rectangular (with continuous, rotating water current around a central baffle). Stocking densities range from 500 to 10,000 PL/m³, with individual sizes of 0.3-3g at harvest, and harvest biomasses of 1-3 kg/m³.
• Stocking post larvae (PL) after the nursery phase (usually up to PL45) instead of PF 10-12 direct from hatcheries can reduce the duration in grow-out ponds by 20-25 days and improve feed conversion ration by 10-20%. This is now one of the strategies to mitigate EHP (and EMS in affected Countries), by stocking larger size PL into grow-out ponds. Two biggest costs in shrimp farming are feed and duration of culture so introduction of the nursery phase helps to reduce risk and improve profitability.

Acute hepatopancreatic necrosis disease (AHPND) earlier known as early mortality syndrome (EMS) or acute hepatopancreatic necrosis syndrome (AHPNS) has been causing significant losses in shrimp farms in China, Vietnam, Malaysia, and Thailand since 2009. The disease affects both black tiger shrimp and Pacific white shrimp and is characterized by mass mortalities during the first 20-30 days of stocking.

Research by the University of Arizona has identified that the disease is caused by the bacterial agent Vibrio parahaemolyticus, which is transmitted orally and colonizes the shrimp’s gastrointestinal tract. This then produces a toxin that causes tissue destruction and dysfunction of the shrimp digestive organ known as the hepatopancreas.

Causes

The disease is caused by a unique strain of Vibrio parahaemolyticus, which can produce toxins responsible for the primary pathology in affected shrimp. Other non-Parahaemolyticus strains such as V. campbellii, V. harveyi, V. owensii, and V. punensis are also found to contain the same toxic genes and may also cause the disease.

Symptoms

• Erratic swimming or swimming near the bottom of the pond
• Reduced growth
• Pale, shrunken or atrophied hepatopancreas
• Whitening of the hepatopancreas
• Reduction in size of hepatopancreas
• Soft texture of the exoskeleton
• Dark spots or streaks on the hepatopancreas
• Hardening of hepatopancreas

Management

• There is no quick fix for EMS/AHPND – once a farm is infected a carefully balanced management plan is required.
• In a worst-case scenario, farmers should be prepared to harvest all ponds at short notice.
• There must implement strict biosecurity measures and a thorough disinfection phase to manage the disease and avoid future outbreaks.
• PL needs to be derived from AHPND-free broodstock. The general health of PL should be checked before stocking, including in stress tests.
• We can manage EMS/AHPND by preventing its further spread and providing better conditions to increase shrimp resistance to it.

Identification of different larval stages is of much importance in the successful operation of a hatchery. As the different larval stages need different types of food and water quality environment, it becomes necessary to identify and segregate them from other groups. Penaeid Shrimps pass through three larval stages before attaining the postlarval stage i.e., nauplius, zoea, and mysis.

Follow the points given below to identify the larval stages of shrimps.

Nauplius stages:

• The first larval stage is known as nauplius.
• The unsegmented body which is Pear shaped with 3 pairs of appendages.
• Moults every 3-5 hours and passes 6 substages (Nauplius 1 - Nauplius 6).
• They are positively phototactic, it swims actively towards weak source of light.
• No feeding due to absence of mouth and alimentary canal.
• After 2 days, the nauplius converts to protozoea by metamorphosis.
• They swim intermittently with their antennae and mandibles.

Protozoea stages:

The body of the zoea is more elongated than the nauplius. The body consists of the carapace, thorax and abdomen. They have functional digestive tract and filter feeders. They feed mainly on unicellular algae present in the medium.

It has 3 sub stages, Protozoea I, II and III. The early protozoea stage has a pair of protruded compound eyes, the next stage is characterized by the presence of a rostrum and the late protozoea stage has a pair of uropods.

• PZ I - Broad head and narrow tail with forked end. Eyes sessile.
• PZ II - Eyes stalked. Rostrum developed.
• PZ III - Abdominal segments develop dorsomedian spines. Uropod bud appears near forked end of tail.

The stages lasts for 3-4 days and is succeeded by Mysis stage.

Mysis stages :

Mysis swims through flexing their abdomen with the head pointing downwards.

It also has 3 sub stages:

M I - No pleopod bud

M II - Pleopod bud appears

M III - Pleopod bud with 2 segments

This stage lasts for 3-4 days and then pass to I post larval stage.

Post Larva:

The postlarva resembles the adult shrimp and it can be distinguished from the mysis stage by the presence of setae on the pleopods which are functional. The postlarvae also prefer to cling to the solid surfaces and the walls of the tank. Substages of postlarvae are called as PL 1, PL 2, PL 3 etc., wherein the number indicates the number of days as postlarva. Postlarvae feed on zooplankton and other dead organic matter. They can tolerate lower salinities.

White spot disease (WSD) is the most serious threat faced by the shrimp farming industry worldwide. WSD was first reported in farmed P. japonicus from Japan in 1992-93, but was thought to have been imported with live infected post-larvae from mainland China. The disease is transmitted vertically from infected brood stock to larvae and horizontally either by ingestion of infected organisms or through carrier organisms. Most crustaceans including all penaeid shrimps (monodon, vannamei, indicus etc.) and crabs can be affected by WSD. All the life stages of shrimp may get infected by this virus.

Causes

White spot disease is caused by a virus called White Spot Syndrome Virus (WSSV). It is a rod-shaped double-stranded DNA virus of 120-150 x 270-290 nm size, assigned to a new virus family, whispoviridae.

Symptoms

• Affected shrimp exhibit anorexia, lethargy, reduced appetite and reddish discoloration
• Sudden reduction in food consumption, loose cuticle with white spots
• Presence of white spots of 0.5 to 2.0 mm in diameter on the inside surface of the carapace, appendages, and cuticle over the abdominal segments.
• In Pacific white shrimp or vannamei shrimp, white spots may not be clearly visible. Mortality of shrimp may start 2-3 days after infection and reach 80-90 per cent within 5-7 days of onset of first mortalities, necessitating emergency harvest.

Diagnosis

WSD may be diagnosed based on gross signs such as the presence of the characteristic white spots, and rapid mortalities. White spots may not be always seen in the early stages of infection in shrimp. WSSV can be detected using polymerase chain reaction (PCR), or with molecular tools such as dot-blot and in situ hybridisation (ISH) tests.

Prevention

• Vertical transmission through infected brooders is also possible, wherein, the virus is transmitted to larvae. Hence, it is always advisable that PCR tested seeds only are stocked in the ponds. There is no treatment for WSSV. Prevention is the only way to avoid the disease.
• Rapid changes in water conditions have to be prevented.
• Avoiding shrimp stress, fresh feeds(crustacean), frequent water exchange is advisable.
• Once infected, treating the pond with chlorine would be of great help to kill infected shrimps and carriers.

Every living thing has to feed to survive. They either act as predators or become prey. Shrimps are preyed upon by birds. They preyed on shrimps and reduce the population of the livestock in the pond or water body. Shrimp farmers go through such losses on a yearly basis. They end up losing a large amount of their investment to predator attacks and because of poor management practices. Bird fencing should be checked daily, if any errors that should be corrected in time to protect the crop. It is necessary, because birds negatively affect shrimp production by transmitting or transporting diseases, weed seeds and parasites from pond to pond or from one facility to another.

Using plastic netting for growing shrimps is effective. Netting makes a great predator barrier.

• The feature of the net is that it is lightweight, durable, and a very easy-to-use barrier.
• It protects the shrimp against herons, egrets, and others.
• Birds such as crow/ water crow pick up the dead and moribund shrimps affected with viral disease from ponds and may drop unaffected ponds, thereby transmitting the virus mechanically. This could be avoided by using bird scares and bird fencing over the pond.
• Birds pick up the infected shrimp from one pond and drop into another pond and thus bird netting is to be installed to avoid cross-contamination from one pond to another.
• Nets used for protecting shrimps from birds come in different grades and have different hole size. The net should also be strong enough to withstand the weight and aggression of the birds. The aquaculture net is UV stabilized and has the capacity to withstand UV rays.
• Nets should also be placed properly to secure the entire pond completely. Birds would get aggressive and try to force their way through the net. A properly installed net would also withstand the pressure and weight of predators to give complete protection.
• Protecting shrimps from birds using nets is very effective. Many shrimp farmers who have problems with predator attacks reported success using a net to protect their shrimps.

Shrimp of the family Penaeidae follow a similar body design to that of most malacostracans. That is, they are laterally compressed, elogate decapods, with a well-developed abdomen adopted for swimming. Each segment is enclosed by a dorsal tergum and ventral sternum.

Shrimp’s body can be separated into two parts. The upper portion of the shrimp is called as cephalothorax and the lower portion is the abdomen segment. The main characteristics of decapods is having an exoskeleton, the shell which is periodically shed (molting) to allow further growth.

Cephalothorax

• The head and thorax are fused together to form cephalothorax
• The shell which protects the cephalothorax is harder and thicker is called carapace
• The stalked eyes of two protrude at the sides of the carapace
• The rostrum (nose) is a saw-like structure and rigid forward extension of the carapace, and can be used for attack or defence.
• The head carries two pairs of antennae. At the base of the second pair of antennae there is a scale-like exopodite, the scaphocerite
• The antenna and antenulles are used as feelers or sensory feelers
• The thorax has 3 pairs of maxillipeds. Maxillipeds are appendages modified to function as mouthparts. The first two maxillipeds work with the anterior mouth parts to manipulate the food, eliminate inedible items, and facilitate the operation of the mandibles and food ingestion. The third pair of maxillipeds is primarily involved with cleaning the mandibles and grooming.
• There are 5 pairs of walking legs ( pereopods), the first 3 being chelate and used for feeding and the last two simple and used for walking.
• The base parts of the pereopods carry the gills
• The exoskeleton of the cephalothorax covers the gills and it also protects the gill chamber ( branchiostegite).

Abdomen

• Abdomen long, longer than the carapace or head
• It consists of the abdominal segments and the tail fan
• The abdomen (pleon) of the penaeid shrimp has six pairs segments, the first 5 with paired pleopods. 
• The swimming legs (pleopods) are located on the first five pairs of the segments of the abdomen, used for swimming.
• The last pair of the segment is the tail fan.
• The tail section of the shrimp has three parts. Two of which are called uropods and the central pointier segment is the telson
• The telson helps the shrimp to control its direction during swimming form the tail fan structure

Litopenaeus vannamei is a decapod crustacean which is native to the Eastern Pacific coast from Sonora, Mexico in the North, through Central and South America as far South as Tumbes in Peru, in areas where water temperatures are normally >20°C throughout the year. Penaeus vannamei live in tropical marine habitats. It has been introduced widely around the world since the 1970s, but especially since 2000, as it has become the principle cultured shrimp species in Asia.

Litopenaeus vannamei (Boone, 1931)

Common name: Whiteleg shrimp

Colour: Coloration normally translucent white, but can change depending on substratum, feed and water turbidity.

Species identification: It has 7-10 teeth on the dorsal rostrum and 2-4 on the ventral side.

Taxonomy:

Order: Decapoda

      Suborder: Natantia

             Infraorder: Penaeidea

                  Superfamily: Penaeoidea

                          Family: Penaeidae

                                   Genus: Penaeus

                                           Species: P. vannamei

Habitat: Depth 0 to 72 m. Bottom mud. Marine (adults) and estuarine (juveniles)

Size: Maximum size 23 cm, with maximum Carapace Length of 9 cm. Maximum weight of female 120 g. Females commonly faster growing and larger than males.

Biology: Males become mature from 20 g and females from 28 g onwards at the age of 6–7 months. P. vannamei weighing 30–45 g will spawn 1,00,000–2,50,000 eggs of approximately 0.22 mm in diameter. Hatching occurs about 16 hours after spawning and fertilization. The first stage larvae, termed nauplii, swim intermittently and are positively phototactic. Nauplii do not feed, but live on their yolk reserves. The next larval stages (protozoea, mysis and early postlarvae respectively) remain planktonic for some time, eat phytoplankton and zooplankton, and are carried towards the shore by tidal currents. The postlarvae (PL) change their planktonic habit about 5 days after moulting into PL, move inshore and begin feeding on benthic detritus, worms, bivalves and crustaceans.