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SQ10603 Aquaculture I nvertebrates Biology

4th PracticalName: CHIN WEI RONG

Matric No.: BS12110088

Course: HS27 AQUACULTURE

Date: 19/04/2013

Title : Dissection of Whiteleg shrimp, Litopenaeus vannamei

Introduction

Litopenaeus vannamei, also known as Pacific whiteleg shrimp (Litopenaeus vannamei,Boone 1931) is naturally distributed in the eastern Pacific Ocean. It is major species offarmed shrimp in Asia, because it grows fast, specific pathogen free diseaseresistance (SDF) and high survival during larval rearing. Litopenaeus vannamei are

amendable to culture at very high stocking densities of up to 150/m in pond culture, ittolerates a wide range of salinities, from 0.5 4.5 ppt, rapid maturation and lowsalinities (around 7 15 ppt).Its scientific classification:

Kingdom : Animalia

Phylum : Arthropoda

Subphylum : Crustacea

Class : Malacostraca

Order : Decapoda

Suborder : Dendrobranchiata

Family : Penaeidae

Genus : Litopenaeus

Species : L. vannamei

The whiteleg shrimp is native to the eastern Pacific Coast of Central and South America;and is considered to be an alien species to Asian countries. However, farmers haveintention of importing this species into Malaysia for its high demand.

Objective

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To study the internal and external anatomy of the whiteleg shrimp, (Litopenaeusvannamei).Materials & Apparatus

Formalin-preserved whiteleg shrimp, dissection tray, dissection tools, electronic balance

Observation

The body of the preserved whiteleg shrimp (Litopenaeus vannamei) in theformalin was in white colour, and its muscle becomes hard. The weight of our specimenis 17.3 grams. In the head section, there are 8 and 2 teeth at the dorsal and ventralside of the rostrum respectively. It has a pair of compound eyes, mouth with jaws(mandibles), a pair of large antennae and a pair of jaws auxiliaries (maxilliped). Thereare also 5 pairs of pereiopods (walking legs) and pleopods (swimmerets). Only the first3 pairs of pereiopods have chela (claw). Besides, there is only one pair of antennaeextending from peduncle of the antenna near the mouth part. And there is one pair ofantennular flagellum and antennal scale too. Tiny hairs were seen on pereiopods,pleopods and antenna.

The specimen was dissected bilaterally. In the cephalothorax, the internal organappears to be in green and red in color. The blood of shrimp is colourless, it contains acopper-rich protein, hemocyanin, which functioned to transport oxygen. The stomach isa sac at the anterior of the carapace, while the heart is located at the posterior end ofthe carapace. Another major organ found in the carapace is the hepatopancreas. Thegills are found near the pereiopods, but within the carapace. There was an intestine(dark colour) found along the dorsal part of abdomen originates from the stomach of

the shrimp to the telson.

Discussion

Shrimp is divided into 2 sections; the first section comprises the head and thethorax fuses together (cephalothorax) and the rest is the abdomen. The cephalothoraxis covered by a carapace which protects the internal organs and the gills. Thehepatopancreas found inside the cephalothorax acts as digestive gland and it isresponsible for the production of digestive enzymes, and absorption of digested food.The color of the internal organ appears to in greenish color probably because of thepresence of the digestive juice.

The antennules/ antennular flagellum found around the mouth part play a role insensing and directing the food particle into the mouth. In the mouthparts of the shrimp,there are several appendages for holding and tearing food. The first 3 pairs of thepereiopods have chela, which helps in grasping the food and passing it on to the mouth.Furthermore, they are also used for walking. The pleopods (swimmerets) aids inlocomotion especially when swimming in mid-water section.

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In mature female, the pleopods function primarily for carrying the eggs until

hatching. The first one or two pairs of pleopods are specialized in the males forfertilization and are known as gonopods. The hairs found on the appendages serve assensory organ to detect mechanical stimulus, such as water pressure and vibration from

predators behind. Chemoreceptors were also believed to found near the mouth part todetect chemical stimulus.

A black color intestine runs from within the cephalothorax, along the dorsal sideof the abdomen, to the hindgut and anus at the telson. This is to transport wastematerial from the stomach and to be excreted through the anus.

Conclusion

This species live at depth of 0 to 72 meters; where adults live in deep marinewater and juveniles or post-larvae stage stay in estuaries, protected from the harshelement of nature (strong wind, current and large predator).

The major disease problems suffered by Litopenaeus vannamei are white spotdisease (WSD), Taura syndrome (TS), Infectious Hypodermal & Haematopoieticnecrosis (IHHNV), Baculoviral Midgut Gland Necrosis (BMN), baculoviral midgut and

Vibrio infections.

In fact, a prospective plan has been drawn up by the Department of FisheriesMalaysia with the aim of gradually increasing shrimp production, particularly

Litopenaeus vannameiproduction. Hence, the study of biology ofLitopenaeus vannamei

and eventually combating the disease that cripple the development of shrimp farming ispivotal.

Reference

1. http://www.fao.org/fishery/culturedspecies/Litopenaeus_vannamei/en2. http://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-

2011-2-3-107-113.pdf

http://www.fao.org/fishery/culturedspecies/Litopenaeus_vannamei/enhttp://www.fao.org/fishery/culturedspecies/Litopenaeus_vannamei/enhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://pelagiaresearchlibrary.com/advances-in-applied-science/vol2-iss3/AASR-2011-2-3-107-113.pdfhttp://www.fao.org/fishery/culturedspecies/Litopenaeus_vannamei/en