by
S.W. LING
FAO/UNDP/TA Regional Fish Culturist for Asia and the Far East
Bangkok, Thailand
Abstract
The paper is based on experiments and observations made at Penang, Malaysia. Macrobrachium rosenbergii is widely distributed in fresh and brackish waters in southeast Asia. It is omnivorous and its feeding behaviour is described. An account is given of moulting, mating and egg-laying and of embryonic, larval and postlarval development. The larva undergoes ll moults before reaching the juvenile stage, but only 8 larval stages are morphologically distinct. At 26 to 28°C, embryonic development takes 19 to 20 days and larval development takes 30 to 45 days; when cultured in ponds, the prawns become fully grown 7 to 8 months after metamorphosis.
The larval stages require brackish water for survival. Under natural conditions, the juveniles migrate to fresh water and adult females release their larvae in the upper parts of estuaries.
BIOLOGIE GENERALE ET DEVELOPPMENT DE Macrobrachium rosenbergii (DE MAN)
Résumé
La communication est fondée sur des expériences et observations faites à Penang (Malaisie). Macrobrachium rosenbergii, largement réparti dans les eaux douces et saumâtres de l'Asie du Sud-Est, est une crevette omnivore dont on décrit les habitudes alimentaires. Le document traite également de la mue, de l'accouplement et de la ponte, ainsi que du développement embryonnaire, larvaire et postlarvaire. La larve mue onze fois avant de parvenir au stade juvénile, mais du point de vue morphologique on ne distingue que huit stades larvaires. A 26–28°C, le développement embryonnaire prend de 19 à 20 jours et le développement larvaire de 30 à 45. Elevées en étang, les crevettes atteignent leur taille adulte de 7 à 8 mois après la métamorphose.
La survie des stades larvaires exige une eau saumâtre. Dans les conditions naturelles, les jeunes émigrent en eau douce et les femelles adultes déposent leurs larves dans la partie amont des estuaires.
BIOLOGIA Y DESARROLLO GENERAL DE Macrobrachium rosenbergii (DE MAN)
Extracto
Informa el autor sobre los experimentos y observaciones realizados en Penang, Malasia. Macrobrachium rosenbergii está ampliamente distribuido en las aguas dulces y salobres del Asia sudoriental; es omnívoro y se describen sus hábitos alimentarios. Explica su autor la muda, apareamiento, desove y desarrollo embriónico, larval y postlarvar. La larva experimenta ll mudas antes de alcanzar la fase juvenil, pero solamente ocho fases larvales son morfológicamente diferentes. Entre 26 y 28°C el desarrollo embrional tarda de 19 a 20 días y el larval de 30 a 45 días; cuando se crían en estanques, los camarones adquieren el pleno desarrollo de 7 a 8 meses después de la metamorfosis.
Las larvas necesitan agua salobre para sobrevivir. En condiciones naturales, los ejemplares juveniles emigran al agua dulce y las hembras adultas desprenden sus larvas en las partes altes de los estuarios.
Macrobrachium rosenbergii, the long-legged giant prawn of fresh and brackish waters, has since time immemorial been highly esteemed as food by people of the tropical countries of Asia and the Far East. The popularity of this prawn has grown rapidly and the demand for it is getting progressively greater. Methods for increasing its production are therefore necessary.
Prawn culture in its true sense is only at its initial stage of development, although various traditional methods of inducing young prawns to enter ponds, “bheris”, tanks, rice fields, etc, are being popularly practised in several countries, especially India and Pakistan. The prawns grow to edible size in these enclosures. Difficulties in getting sufficient supply of young prawns has been a major factor limiting the development and expansion of prawn culture.
The production of young prawns of this species under controlled conditions has been attempted by fisheries' workers in several countries, but without success.
Since the summer of 1959, series of experiments on the breeding, rearing and culturing of this prawn under controlled conditions have been conducted at the Malaysian Fisheries Research Institute, Glugor, Penang, Malaysia, under the FAO/Malaysian Inland Fisheries Development Project. After several years of work and many failures, techniques for rearing the various larval stages and methods for culturing young stages to adults have been developed, and at the same time a considerable number of interesting facts about the biology and habits of this prawn have been observed. The results and observations obtained from these experiments and field work are summarized in this paper.
In view of the great interest of the various nations in this young but highly promising field of aquiculture, it is the hope of the writer that this paper may serve to stimulate greater enthusiasm and to promote further studies leading to a rapid development of large scale prawn culture for food and profit.
2.1 General distribution
The giant prawn, Macrobrachium rosenbergii, locally known in Malaya as “Udang Galah” (Fig. 1), is widely distributed in most of the tropical and subtropical areas of the Indo-Pacific Region, including East Pakistan, India, Ceylon, Burma, Thailand, Malaysia, Indonesia, Philippines, Cambodia and Vietnam. It occurs the whole year round and is present in both fresh and brackish waters. It inhabits most of the rivers, especially the lower reaches which are influenced by tides, but also occurs up to at least 200 km from the coast, and is present in lakes, water reservoirs, mining pools, irrigation canals and even some padi-fields which have direct or indirect access to the rivers.
2.2 Food habits
This prawn is omnivorous and eats frequently and greedily. Common items of food include aquatic worms, aquatic insects and insect larvae, small molluscs and crustaceans, flesh and offal of fish and other animals, grain, seeds, nuts, fruits, algae and tender leaves and stems of aquatic plants. When sufficiently hungry it may even become cannibalistic.
Food is located mainly by smell and touch. When searching for food the filaments of the antennae and antennules sweep about actively. When a large piece of food is found, it is picked up and brought to its mouth by its first and second pairs of thoracic legs together. If small pieces of food, such as grains of rice, are found, they are picked up individually and are brought to the mouth one by one by the pincers of the first pair of thoracic legs. Immediately after the grain is taken by the mouth the empty pincer is again employed for picking up another piece, and an actively feeding specimen may frequently be seen holding two pieces of food, one in each chela, while at the same time there is already one piece in its mouth.
(A) Male
(B) Female
Fig. 1 Macrobrachium rosenbergii, adult.
(A) Male. (B) Female
2.3 Moulting and growth
At moulting, the old cuticle is usually cast in less than ten minutes. The prawn stops other activities, bends its body and exerts strong internal pressure. The internal pressure increases, causing a dorsal transverse split in the membranous part between the carapace and the abdomen. The prawn then bends itself almost in the form of an inverted U, and further internal pressure and repeated flexing of the body soon push part of the body smoothly out through the dorsal split. When much of the body has emerged a sudden jerk frees the entire animal, including all its appendages, from its old shell. Longitudinal splits may also occur along the sides of some segments of some of the larger thoracic appendages. Regenerated missing appendages, which are formed under the old shell, are all set free after moulting.
The frequency of moulting depends on the age of the individual and the amount and quality of food taken. Young specimens moult more frequently than old ones: individuals taking ample amounts of good quality food moult sooner than those taking less or poorer food. Every sexually mature female moults shortly before mating (the premating moult).
Growth rate is rather rapid. Cultured in ponds with good water conditions and ample food, the average growth rate, from young prawns (60 days old, counting from time of metamorphosis) to adults, has been found to be as follows:
| Time in pond | Average length (cm) | Average Weight (g) | |
| Tip of rostrum to tip of telson | Tip of antennal scale to tip of telson | ||
| 1st day | 5.5 | 5.0 | 2.0 |
| 1 month | 7.6 | 6.5 | 4.5 |
| 2 months | 11.0 | 9.5 | 10 |
| 3 " | 14.0 | 12.5 | 25 |
| 4 " | 18.0 | 16.5 | 60 |
| 5 " | 21.0 | 19.5 | 100 |
| 6 " | 22.5 | 20.5 | 125 |
The growth rate of young males and females is about the same. After reaching a length of about 18 cm and a weight of 60 g, the growth rate of females decreases, and there is little growth beyond about 22 cm in length and 120 g in weight. The males keep on growing to about 200 g each.
2.4 Mating and egg-laying
2.4.1 Characteristics of mature male and female When mature, male prawns are considerably larger than females. The second thoracic legs are extremely long and rather thick, the head is big, the abdomen compact with very little space between the pleura, and the genital pores are at the bases of the 5th thoracic legs.
Females are in general smaller than the males, the second thoracic legs are shorter and more slender and the head is smaller. There is a spacious brood chamber below the abdomen, formed by the downward prolongation of the abdominal pleura, and the genital pores are at the bases of the third thoracic legs.
2.4.2 Characteristics of sexually ripe female The ripe ovaries can be seen through the carapace as large orange coloured masses occupying a large portion of the dorsal and lateral parts of the cephalothorax. The abdominal pleura, which are ordinarily bent slightly inwards towards the pleopods, become slightly distended and arched outward, so that the brood chamber is enlarged. The basal segments of the first four pairs of pleopods are elongated and are provided with tufts of long ovigerous setae on their inner margins.
2.4.3 Time for mating Sexually mature males are able to mate at any time, while the females are ready to respond only after completing their pre-mating moult. Under Malaysian conditions mating occurs throughout the year.
2.4.4 Mating The mating process may be observed by introducing a mature male and a sexually ripe female (3 to 6 hours after the pre-mating moult) into an aquarium tank with clean freshwater.
It takes only a few minutes for the male and female prawns to get accustomed to each other and to the new situation. Soon after that, the male starts its courtship display, lifting its head, raising its body, waving its feelers and raising and extending its long and powerful chelate-legs in am embracing gesture, accompanied by intermittent jerking movements. This display continues for 10 to 20 min before the female is successfully won over.
The male then holds the female between its long chelate-legs and at the same time actively cleans the ventral portion of her thoracic shell with its other legs. It takes about 10 to 15 min to complete this cleaning act, and then follows the final mating act which lasts only a few seconds. The female is placed ventral side up while the male presses down from above, bringing its genital pores in close contact with the cleaned ventral thoracic region of the female, and with a sudden vigorous vibration of the pleopods and trembling of the body the sperm is ejected and deposited in one gelatinous mass on the female's ventral median thoracic region.
When several mature female prawns are kept in the same tank, the one that has just completed her pre-mating moult is liable to be attacked by the others. However, in the presence of a mature male, she would be promptly and tenderly protected by him. It is possible that as soon as the pre-mating moult is completed the female secretes a substance which strongly attracts the males.
2.4.5 Egg-laying Egg-laying takes place between 6 and 20 h after mating, depending on how soon mating follows the pre-mating moult of the female. Unmated ripe female prawns also lay eggs within 24 h of the pre-mating moult, but the eggs are not fertilized and drop off in two or three days. The laying of one whole batch of eggs is usually completed within 20 min.
During egg laying the tail of the female prawn bends forward to reach the ventral thoracic region. At the same time the pleopods are extended to form a protected egg passage. The eggs are then extruded through the female genital pores into the brood chamber, first on one side then the other. The chamber between the 4th pair of pleopods is filled first, then those between the 3rd, 2nd and 1st pairs, successively. The eggs are held in bundles like grapes by an extremely thin elastic membrane which is believed to be secreted by the ovigerous setae. The egg bundles adhere tightly to the ovigerous setae of the first four pairs of pleopods.
3.1 Eggs, embryonic development, and hatching
3.1.1 Eggs and fecundity The eggs are slightly elliptical, of long axis 0.6 to 0.7 mm, bright orange in colour, and each has a thin membrane.
A typical mature female of about 80 g in weight and 18 cm in length can produce about 60,000 eggs, as many as 100,000 eggs may be produced by a large female.
Mature females kept in the laboratory are able to lay eggs twice within five months. It is quite possible, therefore, that they may be able to lay eggs 3 to 4 times in one year under natural conditions.
3.1.2 Incubation The female prawn carries her brood of eggs and takes care of them until they hatch. During the whole incubation period, which is about 19 days at 26 to 28°C, the pleopods beat back and forth intermittently to provide aeration for the eggs. Dead eggs and foreign material are carefully and cleverly removed from time to time by the sensitive and versatile first pair of thoracic legs. Starting from the 12th day of incubation, the bright orange colour of the eggs gradually becomes lighter, and in its place a light grey colour slowly develops. The colour gradually deepens to slate grey by the 16th to 17th day of incubation, when the larvae inside the eggs are fully developed.
3.1.3 Segmentation and embryonic development Material for study was obtained from female prawns mated and spawned in aquaria. Fertilization of eggs is assumed to take place at the time of extrusion. Groups of about 40 to 50 eggs can easily be removed from the brood chamber of a berried prawn for study. With frequent changes of water and cleaning of the eggs, they can be kept alive in an embryo-dish or petridish for several days.
Newly fertilized eggs are homogenously granulated. After about 2 h the stellate island of protoplasm containing the nucleus is discernable at the center of the egg and becomes clearly visible about 1 h later.
Counting from the time of fertilization, the first nuclear division starts at about 4 h and is completed within one h; the second nuclear division commences at 6 h and is completed at 7½ h; the third division begins at 8 h and eight nuclei are formed by 9 h. Subsequent divisions take place at about 1 to 1½ h intervals, and segmentation is completed in about 24 h.
Segmentation is illustrated in Fig. 2A-F. The first and second nuclear divisions are completed without any corresponding division of the cell. Four cleavage furrows appear when the third nuclear division is almost completed; they start from four subequidistant points on the surface and extend rapidly almost at right angles to each other to form four quadrants, or blastomeres, whose apexes become joined by a median furrow; each of the four quadrants contains two nuclei. The fourth nuclear division is holoblastic. The fifth and subsequent nuclear divisions are superficial. Advanced segmentation stages show distinct hexagonal markings on the surface.
Nuclei of early segmentation stages are located in the deeper part of the egg. Starting from the eight blastomere stage they tend to appear nearer to the surface, and in the advanced stages all of them reach the surface, as in other Decapoda.
During the second day, after the completion of segmentation, the germinal disc appears on the ventral side of the embryo. Gastrulation takes place by the immigration of cells from the posterior part of the germinal disc, which is soon followed by the formation of the blastopore. A V-shaped germinal band is then differentiated from the blastoderm, occupying a large part of the ventral surface, and assuming the position of the developing embryo.
During the third day, the anterior ends of the germinal bands enlarge in size and become circular, representing the prostomial lobes. The rest of the arms of the germinal bands are narrow and are joined posteriorly with the edge of the blastoporal area. The rudiments of embryonic regions are now formed, and the embryo soon develops into the nauplius embryo stage.
The formation of buds of the nauplius appendages starts when the embryo is about 80 h old. The first to appear are the rudiments of the antennules, which appear near the base of the prostomial lobe, and the rudiments of the mandibles near the posterior end of the germinal band. These are followed by the buds of the antennae, on the sides of the germinal band between the antennules and mandibles.
Fig. 2 Macrobrachium rosenbergii, segmentation and embryonic development.
Times refer to period since fertilization.
(A) 7 h - completion of second nuclear division. (B) 8 h 45 min - third
nuclear division nearly completed, appearance of 4 cleavage
furrows. (C) 8 h 55 min - third nuclear division completed, tips
of the 4 cleavage furrows have met at 2 points from which the
median furrow is developing. (D) 9 h - complete formation of 4
quadrants (blastomeres). (E) 14 h - 32 nuclei. (F) 24 h - completion
of segmentation. (G) 6 days - formation of caudal papilla.
(H) 7 days - formation of optic vesicle. (I) 9 days - eye pigment
developed. (J) 14 days - larva fully formed. (K) 19 days - larva
ready to hatch.
By the beginning of the 5th day, when all the rudiments of the nauplius appendages are well formed, post-nauplius segments begin to form, followed by the appearance of rudiments of the other cephalic appendages. At the same time the formation of the caudal papilla commences and becomes very pronounced at the end of the 6th day, with rudiments of thoracic legs and telson formed (Fig. 2G).
During the seventh day, the optic rudiments develop into a pair of large oval masses, forming the optic vescicles. The rudiments of appendages begin to elongate. The forward growth of the caudal papilla becomes conspicuous, and its tip forms the telson (Fig. 2H).
During the 8th and 9th days, the carapace rudiment is formed; the eyes become pigmented, the heart makes its appearance and starts beating, and the gut is formed (Fig. 2I).
When the embryo is 12 days old it comes to lie parallel to the long axis of the egg. The appendages elongate steadily and organs develop and are fully formed by about the 17th day. The larva keeps growing steadily until hatching on the 19th or 20th day (Fig. 2J, K).
3.1.4 Hatching Under laboratory conditions, it takes about 1 h for individual eggs to hatch, about 4 to 6 h for the whole batch.
Hatching is accomplished by the rapidly increasing internal pressure, developed by the increased volume of the larva and aided by the stretching of the body and movements of appendages, causing the egg membrane to burst. The process of hatching starts with a slow but continuous vibration of the mouthparts of the larva, accompanied by some stretching of its rolled-up body, forcing the egg to elongate gradually. Vibration of the mouthparts becomes more and more vigorous, accompanied by churning of the yolk mass, gradually straightening of the spines of the telson and further stretching of the body. About 45 min from the commencement of hatching the thoracic appendages start to vibrate intermittently, and during the next 10 min these periods of activity become more vigorous and more prolonged until the vibration is continuous. The body continues to stretch, and the telson, which is held over the eyes and head, pushes outward. Suddenly the egg shell breaks, and the telson bursts out, followed by the head, and with a forceful flex and stretch of the body the larva springs out of the egg membrane. In less than 5 min the newly hatched larva starts swimming around actively. During the time of hatching the mother prawn vibrates her pleopods rapidly at intervals to disperse the new hatchlings.
3.2 Larvae
3.2.1 General biology of larvae All larval stages are active swimmers and are planktonic in habit. They are attracted by light, but direct sunlight and other strong lights are avoided. They swim tail first, ventral side up, with the head rather lower than the tail at an oblique angle.
Individuals of early larval stages tend to swim close together in large groups, usually close to the surface of the water. Frequently, the thousands of young larvae in each group swim swiftly in a continuous stream, milling and churning up and down repeatedly. The gregarious habit gradually disappears after the larvae are about 10 days old.
All larval stages require brackish water, corresponding to 20 to 40 percent sea water. Specimens reared in pure freshwater all died within 4 to 5 days. Under natural conditions, larvae may hatch in both brackish and fresh water areas, but those that hatch in fresh water would soon be carried by the flow of water to the estuaries, and those that failed to reach brackish waters within 4 to 5 days would be unable to survive.
All larval stages eat continuously as long as suitable food is available. Their natural food consists mainly of zooplankton, including rotifers, cyclops, copepods and other minute crustaceans, very small worms and larval stages of various aquatic invertebrates. In the absence of living food, minute pieces of organic material, especially those of animal origin (fish, prawn, crab, mollusc, etc) are readily eaten. Very small particles of plant material, especially those rich in starch (grain, seeds, fruits, nuts, etc) are also taken. Food particles are caught with the maxillepeds and thoracic legs while the larvae are swimming. Living food and suspended particles of suitable size are preferred. Liquid foods are not taken, and extremely small food particles are ignored. Large and heavy food particles tend to drag the feeding larvae with them to the bottom and cause considerable mortality.
Fig. 3 Macrobrachium rosenbergii, first and second stage larvae. (A) - (K) First stage: (A) Side view. (B) Dorsal view of head. (C) Antennule. (D) Antenna. (E) Maxillule. (F) Right mandible, distal portion. (G) Left mandible, distal portion. (H) Maxilla. (I) Maxilliped 1, most of exopod omitted. (J) Maxilliped 3, with biramous buds of thoracic legs 1 and 2 shown behind. (K) Telson.
(L) - (O) Second stage: (L) Dorsal view. (M) Maxillule (N) Right mandible, distal portion. (O) Thoracic leg 2, with buds of legs 3 and 4 shown behind.
3.2.2 Development of larval stages From hatching until metamorphosis into juveniles, the larvae undergo ll moults, but only eight morphological stages can be recognized distinctly. From the first to the fifth stage, each moult results in a new stage; from the sixth stage to the juvenile stage, two moultings occur between two consecutive morphological stages. For the sake of convenience, these eight stages are described below as the eight larval stages. The growth rate of the larvae is fairly even during the first three larval stages, but then becomes irregular.
First larval stage (1 to 2 days from hatching) (Fig. 3A-K)
Length: 2.0 to 2.2 mm (from tip of rostrum to tip of telson).
Body: transparent, antennular peduncle slightly bluish, eyes light brownish on their outer portion. Chromatophores similar to those of other palaemonid larvae; the 2 pairs on abdominal segment III are very prominent, with dendrites reaching abdominal segment II.
Rostrum: slender, curved slightly downward at tip, reaching to about 2/3 length of basal segment of antennular peduncle. Antereo-ventral margin of carapace produced into small spine.
Eyes: large, sessile.
Antennule: peduncle narrow, long, unsegmented; inner flagellum long, plumose; outer flagellum rectangular, 3 long aesthetes, 1 long seta, 1 short stout plumose seta.
Antenna: peduncle unsegmented; flagellum unsegmented, 1 long and 1 short apical setae; exopod with about 5 annulations in distal half, 9 long plumose setae, 2 short outer setae.
Mandibles: right and left mandibles similar in size and shape; right mandible with 1 large and 2 medium teeth on incisor part, 4 to 5 small spine-like teeth on molar part; left mandible with 2 teeth on incisor part, none on molar part.
Maxillule: very small; palp (endopod) prominent, 2 short spines at apex; proximal lacinia (of masticatory process) about same size as palp, 4 setae at tip; distal lacinia about twice as large as proximal, 2 large and 2 small teeth at distal end.
Maxilla: scale (exopod) with 5 long plumose setae on outer edge, proximal seta largest; endopod with long terminal non-plumose spine, 2 setae on thicker proximal portion; protopod with 3 lobes, proximal with 4 setae, others with 2 setae each.
Maxilliped 1: base almost round, 3 setae on upper margin; endopod finger-shaped, 3 terminal setae; exopod long, 4 long plumose setae at apex.
Maxillipeds 2 and 3: endopod 4-segmented, 1 finely serrated claw and 2 setae at apex; exopod long, 4 long plumose setae at apex.
Fig. 4 Macrobrachium rosenbergii, third, fourth, fifth and sixth stage larvae. (A) - (F) Third stage: (A) Antennule. (B) Antenna. (C) Left mandible, distal portion. (D) Maxilliped 1. (E) Thoracic leg 3 with buds of legs 4 and 5. (F) Telson and uropods.
(G) - (K) Fourth stage: (G) Thoracic leg 2. (H) Thoracic leg 3. (I) Thoracic leg 4 in bud form. (J) Thoracic leg 5. (K) Telson and uropods.
(L) Fifth stage: telson and uropod.
(M) - (R) Sixth stage: (M) Maxilla. (N) Antennule. (O) Maxilliped 1 (P) Pleopods in different early stages of formation. (Q) Pleopods in later stages of formation. (R) Telson and uropod.
Thoracic legs 1 and 2: biramous buds.
Telson: triangular; posterior edge broad, slightly concave, notched in middle, 7 pairs stout plumose setae (2 lateral pairs plumose only on inner edge), many small stout spines.
Second larval stage (3 to 5 days from hatching) (Fig. 3L-0)
Length: 2.3 to 2.4 mm.
Prominent red chromatophore with light brown dendrites on ventral side of eye stalk; pale yellow pigment on frontal portion of eyes.
Antero-ventral margins of carapace produced further forward to form the pterygostomian spines. Supraorbital spine very prominent.
Eyes large, stalked. Antennular peduncle 2-segmented. Antennal flagellum carrying 2 long and 1 short setae at apex. Right mandible with 5 stout teeth on incisor part, innermost curved and serrated on upper margin; molar region with 5 short teeth. Left mandible with 3 long teeth on incisor part and 2 short teeth on molar region. Maxillule with 2 short setae at apex of palp; proximal lacinia with 4 long teeth; distal lacinia with 4 long and 3 short teeth. Exopod of maxilla with 7 long plumose setae.
Maxilliped 1: Endopod of maxilliped 1 shorter, with 3 terminal and 2 lateral setae. Thoracic legs 1 and 2 each with large 5-segmented endopod ending in long curved smooth spine; exopods large, setose. Rudimentary buds of legs 3 and 4 present.
Telson bears additional (8th) pair short non-plumose setae at centre of posterior edge.
Third larval stage (5 to 8 days from hatching) (Fig. 4A-F)
Length: 2.7 to 2.8 mm.
One epigastric spine behind base of rostrum. Peduncle of antennule 3-segmented. Antennal flagellum 2-segmented; exopod with 12 to 13 long plumose setae, annulation confined to apex. Exopod of maxilla with 9 plumose setae. Thoracic leg 3 similar to 1 and 2. Buds of thoracic legs 4 and 5 present.
Articulation between 6th abdominal segment and telson. Lateral and central pairs of telson setae (1st and 8th pairs) not plumose. Uropods present; outer lobe more than twice as long as inner, with 6 long plumose setae on distal portion; inner lobe without setae.
Fourth larval stage (8 to 12 days from hatching) (Fig. 4G-K)
Length: 2.9 to 3 mm.
Prominent chromatophore on ventral side of 4th abdominal segment. Distinct red and blue pigment on thoracic leg 2.
Carapace bears two median dorsal (epigastric) spines behind base of rostrum, both spines with 2 to 3 teeth on front edge.
Antennal exopod with 15 to 16 plumose setae and 1 apical spine; no annulations. Thoracic leg 4 a biramous bud. Leg 5 large, segmented, with very long curved terminal spine; no exopod.
Telson much narrower; posterior width less than twice anterior width and only about half length of lateral. Exopod and endopod of uropod articulate with protopod; exopod bears 9 to 10 long plumose setae, endopod 6 to 7 setae.
Fig. 5 Macrobrachium rosenbergii, seventh and eighth stage larvae. (A) - (F) Seventh stage: (A) Antennule. (B) Maxilliped 1. (C) Maxilliped 2, most of exopod omitted. (D) Thoracic leg 2, chela. (E) Pleopod 1. (F) Pleopod 2.
(G) - (P) Eighth stage: (G) Antennule. (H) Antenna. (I) Maxillule. (J) Right mandible. (K) Left mandible. (L) Maxilla. (M) Maxilliped 2, most of exopod omitted. (N) Rostrum. (O) Thoracic leg 2, chela. (P) Telson, posterior portion.
Fifth larval stage (11 to 17 days from hatching) (Fig. 4L)
Length: 3.2 to 3.3 mm.
Chromatophore on thoracic leg 2 very prominent, with red centre and blue dendrites.
Epigastric spines each with 4 to 5 teeth.
Proximal end of exopod of maxilla bears 2 long backwardly-directed plumose setae. All 5 pairs thoracic legs segmented; 5th pair longest, remains uniramous.
Telson rectangular, twice as long as broad; 3 pairs lateral setae, 5 pairs on posterior margin; outer 4 pairs and innermost pair smooth, other 3 pairs plumose. Exopod of uropod with 13 to 14 long plumose setae, endopod 9 to 10 setae.
Sixth larval stage (15 to 24 days from hatching) (Fig. 4M-R)
Length: 3.4 to 3.5 mm.
Transparent; pale salmon-pink, deeper at head end and paler towards telson. Chromatophore on ventral eye stalk very prominent, with brownish-red centre and red and yellowish dendrites; chromatophore on thoracic leg 2 remains prominent, with red centre, blue dendrites and some green spots; chromatophore on ventral side of abdominal segment 4 greatly enlarged, with deep blue centre and dendrites of red, blue and yellow.
Inner flagellum of antennule elongated, 3 long setae at apex; outer flagellum segmented, 6 to 7 aesthetes in 2 groups. Antennal flagellum slightly longer than scale. Endopod of maxilliped 2-segmented, 3 long and 1 short spines at apex. Pleopod buds on abdominal segments 1 to 5; differences in development from specimen to specimen; 2nd, 3rd and 4th pairs usually more advanced; larger buds biramous.
Telson much elongated; posterior width only about 2/3 anterior width and about 1/5 length; marginal spines and setae smooth, apart from 2 pairs next to central pair. Uropod with 12 to 16 plumose setae on endopod, 16 to 20 on exopod.
Seventh larval stage (22 to 32 days from hatching) (Fig. 5A-F)
Length: 4.0 to 4.5 mm.
Inner flagellum of antennule 3-segmented; outer flagellum split longitudinally: inner part faintly segmented, with 10 to 11 aesthetes in 4 groups; outer part longer, forms flagellum proper. Thoracic legs 1 and 2 chelate. All 5 pairs pleopods biramous, exopod and endopod both with plumose setae.
Telson narrower and longer; 3 pairs short lateral setae, 4 posterior pairs; inner 2 pairs plumose.
Eighth (last) larval stage (30 to 45 days from hatching) (Fig. 5G-P)
Length: 5.0 to 5.8 mm.
Rostrum with 4 to 9 teeth on upper margin, 4 short plumose setae between front epigastric spine and hind rostrum tooth.
Inner flagellum of antennule 5 to 6 segmented; shorter outer flagellum with 14 to 15 aesthetes in 6 groups; longer outer flagellum 6 to 8 segmented. Antennal flagellum many segmented, about 1½ times as long as scale.
Left mandible with 3 large teeth and 5 to 6 slender ones on incisor part, 3 to 4 short teeth on molar area. Right mandible with 2 big blunt teeth and 8 to 10 long slender ones on incisor area, molar region with 2 stout and 4 short teeth. Palp of maxillule with only 1 seta and small protuberance at tip; proximal lacinia with 8 to 10 fine setae at apex, distal lacinia with 7 to 8 long and 3 to 4 short teeth. Scale of maxilla with about 50 plumose marginal setae; distal and median lobes of protopod well developed, finger shaped, with both plumose setae and spines; proximal lobe reduced. Basal endite of maxilliped 1 with many slender spines; endopod 3-segmented; exopod with 10 plumose setae on the outer edge of the enlarged basal half. Endopod of maxilliped 2 finger-shaped, 5-segmented, with 2 stout spines, 1 terminal and 1 subterminal. Thoracic leg 2 the largest.
Telson very much elongated; posterior portion narrow, with 5 pairs spines on posterior edge, the inner 2 pairs plumose.
Fig. 6 Macrobrachium rosenbergii, first juvenile stage. (A) Antennule. (B) Rostrum. (C) Right mandible. (D) Left mandible. (E) Maxillule. (F) Maxilla. (G) Maxilliped l. (H) Maxilliped 2. (I) Maxilliped 3. (J) Thoracic leg 1, with degenerating exopod. (K) Thoracio leg 2, basal portion with degenerating exopod. (L) Thoracic leg 4. (M) Pleopod 1. (N) Pleopod 4. (O) Telson and uropod. (P) Telson, posterior portion.
3.3 Juveniles
3.3.1 General habits Juveniles cease to be permanently pelagic as soon as they metamorphose from the last stage larvae. They settle to the bottom as crawlers or cling to vegetation and submerged objects. They feed readily on tiny worms, small crustaceans, insect larvae and a large variety of small pieces of organic material, both of plant and animal origin. They grow rapidly, moult every 5 to 10 days, and are able to attain a length of about 5 cm in 2 mo.
Under natural conditions, newly transformed juveniles usually remain in brackish water areas for a week or two then start migrating slowly upstream into water of lesser salinity. When they are about 1 mo old they are able to migrate quite fast. After 2 mo they are able to swim against swift currents or cross rapids by crawling. They will climb over bunds or dams 2 to 3 m high, provided there is a little water dripping over the dam. During the rainy season they are capable of migrating through temporary shallow streamlets into ponds, pools, padi-fields and other types of water which are normally inaccessible to them during the dry season. The fact that adults have occasionally been caught in waters over 200 km away from brackish water areas indicates the great distance they are able to cover.
3.3.2 Characteristics of newly transformed juveniles (Fig. 6)
Length: from tip of rostrum to tip of telson, 6.0 to 6.5 mm; from tip of antennal scale to tip of telson, 6.0 to 6.6 mm.
Translucent; light orange-pink in head end, lighter toward abdomen and telson; brown chromatophores at base of eyes and front of carapace; red on sides and hind part of carapace, on sides of first 5 abdominal segments and at bases of uropods; orange and red pigment along ventral side of abdominal segments 2, 3 and 4, joining large conspicuous red and blue chromatophore at ventral side of abdominal segment 4.
Rostrum lancet-shaped; 11 teeth above, 3 to 5 below, fine plumose setae in spaces between teeth.
Inner flagellum of antennule 14 to 16-segmented; longer outer flagellum 13 to 15-segmented; about 16 aesthetes in 6 groups. Antennal flagellum about 3 times length of scale. Incisor and molar parts of mandible distinctly separated, forming a “V” shaped structure on a long base. Incisor part of each mandible with 3 large teeth; molar part of right with 4 short blunt teeth; molar part of left with 1 pair of blunt teeth, 2 to 3 small teeth at outer corner and large molar surface surrounded by many slender teeth. Maxillule similar to that of last larval stage. Maxilla with distal and median lobes of protopod elongated, with many fine apical setae; proximal lobe disappeared. Maxilliped 1 foliaceous: 2 large setose endites; large setose outer lobe at base of exopod. Endopod of maxilliped 2, 5-segmented, the 2 distal segments with spines and setae. Endopod of maxilliped 3, 4-segmented, setae in rows on terminal segment; exopod with 4 long apical plumose setae and shorter lateral setae. Second pair of legs the largest; degenerating exopods on legs 1 to 4 become reduced to knobs at next moult.
Only 2 pairs of spines on posterior edge of telson, inner pair plumose; anterior 2 pairs of spines (previously lateral) now dorsal.
Practical methods for rearing and culturing M. rosenbergii on a large scale are described by Ling (in press).
Fujimura, T., 1966 Notes on the development of a practical mass culture technique of the giant prawn Macrobrachium rosenbergii. Paper presented to the Indo-Pacific Fisheries Council, 12th session, IPFC/C66/WP47
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John, M.C., 1947 Bionomics and life-history of Macrobrachium rosenbergii. Bull.Res.Inst. Univ.Kerala(c), 5(1): 93–102
Ling, S.W., 1962 Studies on the rearing of larvae and juveniles and culturing of adults of Macrobrachium rosenbergii (de Man). Tech.Pap.Indo-Paci.Fish.Coun., (57): 15p.
Ling, S.W., 1964 A general account on the biology of the giant freshwater prawn, Macrobrachium rosenbergii and methods for its rearing and culturing. Paper presented to the Indo-Pacific Fisheries Council, 11th session, 16–31 October, 1964, Contributed paper No. 40
Ling, S.W., 1969 Methods of rearing and culturing Macrobrachium rosenbergii (de Man). FAO Fish.Rep., (57) vol.3:607–19
Ling, S.W. and A.B.O. Merican, 1961 Notes on the life and habits of the adults and larval stages of Macrobrachium rosenbergii. Proc.Indo-Pacif.Fish.Coun., 9(2): 55–60
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Acknowledgements
The author wishes to express his gratitude to Mr. Soong Min Kong, Director of Fisheries, Malaysia, and his senior Fisheries Research Officer for their deep interest and enthusiastic support for this project, to Mr. A. B. O. Merican, Fisheries Research Officer (Inland), and other members of the prawn working team for their close cooperation and zealous participation in this work, and to all FAO colleagues and friends who have contributed valuable advice and assistance, either directly or indirectly, in making the smooth and rapid progress of this work possible.
