Prawns exhibit diverse habitat preferences, thriving in various aquatic environments beyond just freshwater. While some species are found in freshwater, many adapt to other settings, showcasing a broad range of water conditions.
Understanding What Prawns Are
Prawns are aquatic crustaceans belonging to the order Decapoda, characterized by possessing ten legs and an external skeleton. Their bodies are segmented, typically elongated and cylindrical, and can display a variety of colors such as black, pink, white, or grey. Biologically, prawns are classified within the suborder Dendrobranchiata. Like other crustaceans, they periodically shed their exoskeleton to grow.
Prawn Habitats: A Diverse Range
Prawns occupy a wide array of aquatic environments, including freshwater, saltwater (marine), and brackish water. Many species are predominantly found in freshwater systems, such as rivers, lakes, ponds, and streams.
Some freshwater prawns, however, require brackish water for their larval development, with the juveniles then migrating upstream into freshwater. Saltwater environments are home to numerous prawn species that spend their entire lives in marine conditions. Brackish water, which is a mixture of fresh and salt water often found in estuaries or river mouths, also supports many prawn populations. Many species exhibit life cycles that involve migrations between these different salinity zones for various life stages, including breeding. Prawns possess osmoregulatory capabilities, allowing them to regulate internal salt concentrations and adapt to fluctuating salinities.
Prawns Versus Shrimp: A Clearer Picture
The terms “prawn” and “shrimp” are often used interchangeably, but they represent distinct biological groups. Prawns belong to the suborder Dendrobranchiata, while most shrimp are classified under the suborder Pleocyemata. Anatomical differences include:
- Prawns have branching gills, unlike the plate-like gills found in shrimp.
- Prawns have a generally straighter body, with exoskeleton segments overlapping from front to back. Shrimp typically have a more curved body, where the second segment overlaps both the first and third.
- Prawns commonly have claws on three pairs of legs, with the second pincer being larger. Shrimp usually possess claws on two pairs of legs, with their front pincers being the largest.
- Prawns release fertilized eggs directly into the water, while shrimp carry eggs attached to their underside.
Notable Freshwater Prawns
The Giant River Prawn, Macrobrachium rosenbergii, is an example of a freshwater prawn. This species is native to the Indo-Pacific region, spanning from India through Southeast Asia to Northern Australia. Its considerable size makes it a commercially significant species, widely cultivated in aquaculture for food production. While adult Giant River Prawns inhabit freshwater, their early larval stages require brackish water for development. After developing in these slightly saline conditions, post-larvae migrate upstream to complete their life cycle in freshwater.