Giant river prawn
Encyclopedia
Macrobrachium rosenbergii, also known as the giant river prawn, giant freshwater prawn, Malaysian prawn, freshwater scampi (especially in India), or cherabin, is a species of freshwater
shrimp
(not a prawn
or scampo in terms of phylogeny, although colloquially "prawn" can refer to freshwater shrimp or true prawns) native to the Indo-Pacific
region, northern Australia
and Southeast Asia. This species (as well as other Macrobrachium
) is commercially important for its value as a food source.
While M. rosenbergii is considered a freshwater species, the larva
l stage of the animal depends on brackish water. Once the individual shrimp has grown beyond the plankton
ic stage and become a juvenile, it will live entirely in freshwater.
Male M. rosenbergii have a strict hierarchy: the territorial BC males dominate the OCs, which in turn dominate the SMs. The presence of BC males inhibts the growth of SMs and delays the metamorphosis of OCs into BCs; an OC will keep growing until it is larger than the largest BC male in its neighbourhood before transforming. All three male stages are sexually active, and females who have undergone their pre-mating moult will co-operate with any male to reproduce. BC males protect the female until their shell has hardened; OCs and SMs show no such behaviour.
s 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 three weeks. Females lay 10,000–50,000 eggs up to five times per year.
From these eggs hatch zoeae, the first larval stage of crustacean
s. They go through several larval stages before metamorphosing into postlarvae, at which stage they are 0.28–0.39 in (0.7112–0.9906 ) long and resemble adults. This metamorphosis usually takes place about 32 to 35 days after hatching. These postlarvae then migrate back into freshwater.
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
(not a prawn
Prawn
Prawns are decapod crustaceans of the sub-order Dendrobranchiata. There are 540 extant species, in seven families, and a fossil record extending back to the Devonian...
or scampo in terms of phylogeny, although colloquially "prawn" can refer to freshwater shrimp or true prawns) native to the Indo-Pacific
Indo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
region, northern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
and Southeast Asia. This species (as well as other Macrobrachium
Macrobrachium
Macrobrachium is a genus of freshwater shrimp characterised by the extreme enlargement of the second pair of pereiopods, at least in the male...
) is commercially important for its value as a food source.
While M. rosenbergii is considered a freshwater species, the larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
l stage of the animal depends on brackish water. Once the individual shrimp has grown beyond the plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic stage and become a juvenile, it will live entirely in freshwater.
Description
M. rosenbergii can grow to a length of over 30 centimetres (11.8 in).Morphotypes
There are three different morphotypes of males. 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 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 body.Male M. rosenbergii have a strict hierarchy: the territorial BC males dominate the OCs, which in turn dominate the SMs. The presence of BC males inhibts the growth of SMs and delays the metamorphosis of OCs into BCs; an OC will keep growing until it is larger than the largest BC male in its neighbourhood before transforming. All three male stages are sexually active, and females who have undergone their pre-mating moult will co-operate with any male to reproduce. BC males protect the female until their shell has hardened; OCs and SMs show no such behaviour.
Life cycle
In mating, the male deposits spermatophoreSpermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
s 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 three weeks. Females lay 10,000–50,000 eggs up to five times per year.
From these eggs hatch zoeae, the first larval stage of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s. They go through several larval stages before metamorphosing into postlarvae, at which stage they are 0.28–0.39 in (0.7112–0.9906 ) long and resemble adults. This metamorphosis usually takes place about 32 to 35 days after hatching. These postlarvae then migrate back into freshwater.