Macrobrachium rosenbergii is a commercially important species of palaemonid freshwater prawn. It is native throughout the tropical and subtropical areas of the Indo-Pacific region, from India to Southeast Asia and Northern Australia. While M. rosenbergii is considered a freshwater species, the larval stage of the animal depends on brackish water. Once the individual shrimp has grown beyond the planktonic stage and becomes a juvenile, it lives entirely in fresh water.
In English, it is commonly known as the giant river prawn, giant freshwater prawn, Malaysian prawn, freshwater scampi (India), or cherabin (Australia). Locally, it is known as golda chingri () in Bangladesh and India, udang galah in Indonesia and Malaysia, uwáng or uláng in the Philippines, (กุ้งแม่น้ำ) or (กุ้งก้ามกราม) in Thailand, and Thailand prawn in Southern China and Taiwan (Chinese: Tàiguó xiā 泰國蝦).
It is one of the biggest freshwater prawns in the world, and is widely cultivated in several countries for food. Due to accidental releases, the giant freshwater prawn has also been introduced to parts of Africa, China, Japan, New Zealand, the Americas, and the Caribbean.
Description M. rosenbergii can grow to a length over , with total lengths of for males and for females. Females can be distinguished from males by their wider abdomens and smaller second pereiopods (walking legs), which in this species bear the major chelae (large pincers). The genital openings are found on the body segments containing the fifth pereiopods in males and the third pereiopods in females.
They are predominantly brownish in colour, but can vary. Smaller individuals may be greenish and display faint vertical stripes. The rostrum is very prominent and contains 11 to 14 dorsal teeth and 8 to 11 ventral teeth. The first pair of walking legs is elongated and very thin, ending in delicate claws (chelipeds), which are used as feeding appendages. The second pair of walking legs is much larger and more powerful, especially in males. The movable claws of the second pair of walking legs are distinctively covered in dense bristles (setae) that give them a velvety appearance. The colour of the claws in males varies according to their social dominance.
Morphotypes Three different male morphotypes, which correspond to their social dominance, are widely recognized. The first stage is called "small male" (SM); this smallest stage has short, nearly translucent claws. If conditions allow, small males grow and metamorphose into "orange claws" (OC), which have large orange claws on their second chelipeds, which may have a length of 0.8 to 1.4 times their body size. OC males later may transform into the third and final stage, the "blue claw" (BC) males. These have blue claws, and their second chelipeds may become twice as long as their bodies. Senescent blue claw individuals are sometimes recognized as "old blue claws" (OBC), characterized by a smaller abdominal length compared to the carapace and major cheliped lengths.
Males of M. rosenbergii have a strict hierarchy; the territorial BC males dominate the OCs, which in turn dominate the SMs. The presence of BC males inhibits the growth of SMs and delays the metamorphosis of OCs into BCs; an OC keeps growing until it is larger than the largest BC male in its locale before abruptly transforming into the BC phase. All three male stages are sexually active, and females that have undergone their premating moult cooperate with any male to reproduce. BC males protect the females until their shells have hardened; OCs and SMs show no such behaviour.
Life cycle
In mating, the male deposits spermatophores on the underside of the female's thorax, between the walking legs. The female then extrudes eggs, which pass through the spermatophores. The female carries the fertilised eggs with her until they hatch; the time may vary, but is generally less than 3 weeks. Females lay 10,000–50,000 eggs up to five times per year.
From these eggs hatch zoeae, the first larval stage of crustaceans. They go through several larval stages in brackish water before metamorphosing into post-larvae, at which stage they are long and resemble adults. This metamorphosis usually takes place about 32 to 35 days after hatching. These post-larvae then migrate back into fresh water.
The giant freshwater prawn lives up to 3 years of age.
Relation to humans M. rosenbergii is widely eaten in Southeast Asian countries, its native range. They are also commonly used in indoor shrimping venues. The species is aquacultured throughout the tropics.
In research Professor Amir Sagi and his research group at Ben-Gurion University of the Negev have studied the IAG physiological sexual switch in decapods Ardavan Farhadi et al., 2021. The Regulatory Mechanism of Sexual Development in Decapod Crustaceans. Frontiers in Marine Science, 8, pp. 1-19 (references in pages 13-18; Citations within the text).Kenji Toyota, 2024. Crustacean endocrinology: Sexual differentiation and potential application for aquaculture. General and Comparative Endocrinology, Vol. 356, 15 September 2024, 114578. and their associated gene expression.ZHOU Huan et al., 2024. Protein Interaction of IAG in Cherax Quadricarinatus Based on Nuclear Systaem Yeast Two-Hybrid Technology. Acta Hydrobiologica Sinica, 48, pp. 1095-1101 (references 2 & 14).Miao M. CRISPR/Cas9-Mediated Gene Mutation of EcIAG Leads to Sex Reversal in the Male Ridgetail White Prawn Exopalaemon Carinicauda. Front Endocrinol (Lousanne), 21 November 2023 (references: 1, 17, 20, 22, 24 & 52). their research has also examined genetic functions related to crustacean investigating reproduction as well as genome editing in prawns using application of CRISPR.
The research group has also developed monosex biotechnologies, including the use of temporal RNA interference (RNAi) to produce all male crustacean populations.Tao Wang et al., Molecular Mechanisms of Sex Determination and Differentiation in Decapod Crustaceans for Potential Aquaculture Applications: An overview. Reviews in Aquaculture, 23 May 2024 (references: 4, 5, 11, 26, 50, 62, 64, 180, 231, 238 & also in the recomanded articles at the 1st page.). Monosex crustacean aquaculture technologies have been applied in countries including Vietnam, Thailand, China, Malaysia, Israel.Phansawat, P., Keetanon, A., Rairat, T., Pichitkul, P., Poldetch, P., & Chuchird, N., 2022. Benefits of Male Monosex Culture of Giant Freshwater Prawn (Macrobrachium rosenbergii): Improving Growth Performance, Production Yield, and Profitability. Journal of Fisheries and Environment, 46, pp.157-168. Sagi is also a co-founder of Enzootic Ltd. a biotechnology focused on all-female crustacean culture.
Research has investigated the potential use of prawns as biocontrol agents for invasive and pest species.Yingying Wang et al., Efficacy of Giant River Prawn Macrobrachium rosenbergii in Controlling the Invasive Snail Pomacea canaliculata: Implications for Ecological Farming. Diversity, 15, September 2023, pp. 1-12 (references: 42, 57 and also 2 recomanded articles). The Sagi lab development of monosex prawn that have been studied for use in biological control applications in various parts of the world. The Sagi laboratory has also developed monosex prawn technologies that have been studied for use in biological control applications in various parts of the world. Hoover et al., 2019. Modelled effects of prawn aquaculture on poverty alleviation and schistosomiasis control. Nature Sustainability 2: 611-620.
References
External links How to Know Gender of Macrobrachium rosenbergii. Macrobrachium rosenbergii diet. Prove Macrobrachium rosenbergii can upsize in wild. How to catch Macrobrachium rosenbergii. FAO Fisheries & Aquaculture: Macrobrachium rosenbergii - 2021 Aquaculture of Texas