Giant River Prawn

• The males form three castes of different appearance and behaviour: the dominant blue-clawed males, the orange-clawed males and the small transparent ones, and an individual can change caste over its life.
• Its larvae die in pure fresh water: they need salinity to complete their metamorphosis, something that held back its farming for decades until it was discovered in the 1960s.
• Its males come in three distinct morphotypes that coexist in the same population, and they are not age stages but alternative strategies.
• The blue-claw male is the dominant one: huge, territorial, with extremely long chelae, he defends a territory and monopolises freshly moulted females.
• The orange-claw male is a contender in transition, and the small-claw male practises sneaking: he slips in and fertilises females while the dominant male is off guard.
• A male can change morphotype over the course of his life, and the presence of a dominant male holds back the development of the others.
• It is the most farmed freshwater prawn in the world, with major production in South-East Asia and Latin America.
• Its larvae do not survive in fresh water: they need brackish water, a requirement that means its farming demands hatcheries with controlled salinity.
• Its chelae can exceed the length of the entire body.

Skeleton type

Invertebrate - chitin exoskeleton (crustacean)

Habitat and environment

Tropical rivers, lagoons and estuaries, with larvae that need brackish water

Sources consulted: Wikipedia (es): Macrobrachium rosenbergii