Freshwater makes up about only 2.5 per cent of all the water on Earth. Freshwater ecosystems are not only essential for our own survival but also support rich biodiversity, supporting about 5% of all species on the planet. Today’s species is common in our daily life, but most people may ignore its astonishing biology.
The Oriental river prawn, 𝘔𝘢𝘤𝘳𝘰𝘣𝘳𝘢𝘤𝘩𝘪𝘶𝘮 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 (De Haan, 1849) is a freshwater shrimp from the Palaemonidae family. It possesses a pair of long chelipeds (second pair of legs that bear large chelae or pincers), and black stripes on the side of its carapace (upper section of the exoskeleton which covers the head). It is widely distributed in tropical and subtropical Asian regions. In Hong Kong, a wide range of habitats are favourable for this species, such as lowland streams, ponds and reservoirs. Being an omnivore, it has a rich diet, feeding on organic matter, invertebrates as well as fish. Even though it is a tiny creature (8 cm in length) in our eyes, it has high adaptability to withstand low temperatures (down to 5 degrees). Owing to its high resistance, it can survive longer.
The elongated chelipeds of 𝘔. 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 are big and strong. Apart from hunting, they are used for self-defence, in particular against other individuals as this species is territorial. When an invader intrudes its home, it will wave its chelipeds to intimidate the invader - a prawn version of muscle flexing. Moreover, during the breeding season, 𝘔. 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 will be more aggressive in protecting its homeland to preserve its mate and offspring. Therefore, if you are not invited to visit its home, you should keep a safe distance from it.
Interestingly, 𝘔. 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 has a high tolerance for salinity, allowing it to live in brackish water or in freshwater habitats. Thus, its growing condition is unrestricted. This means that its entire life cycle can be in freshwater, breeding directly and growing in freshwater habitats surrounded by land (landlocked). Alternatively, it can also be amphidromous, meaning that spawning occurs in freshwater while the larvae will migrate to saline water to grow until the juvenile stage. 𝘔𝘢𝘤𝘳𝘰𝘣𝘳𝘢𝘤𝘩𝘪𝘶𝘮 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 is one of the few freshwater prawns to be non-obligatory amphidromous species.
In Hong Kong and many other surrounding regions, 𝘔. 𝘯𝘪𝘱𝘱𝘰𝘯𝘦𝘯𝘴𝘦 is an economically valuable species for aquaculture due to its fast growth rate and strong reproductive ability. We should be grateful that these amazing species provide us with food but we should also remain vigilant that it is not done at the cost of other freshwater species and their overall biodiversity.
Text: Edmond Lee
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