Prawns are aquatic crustaceans found globally in diverse habitats, from freshwater rivers to vast oceans. Understanding their dietary habits is important for comprehending their role in aquatic ecosystems, as their feeding behaviors influence nutrient cycling and food web dynamics.
What Prawns Typically Consume
Prawns are omnivorous scavengers, consuming a wide variety of available food sources. Their diet largely consists of detritus—decaying organic matter from dead plants, animals, and microorganisms on the substrate. They also graze on various forms of algae, including microscopic algae, biofilm, green algae, and diatoms. Their digestive systems process food quickly, requiring a near-constant intake of small particles.
Beyond plant-based materials, prawns also consume small invertebrates like worms, tiny crustaceans, mollusks, polychaetes, and other benthic organisms. Prawns are opportunistic feeders, adapting their diet to what is most readily available. In situations of food scarcity or during molting, cannibalism can occur.
How Prawns Find and Eat Food
Prawns use sensory organs and specialized appendages to locate and ingest food. Their antennae play a primary role through chemoreception, detecting chemical cues (smell and taste) in the water from a distance. Chemo-sensory hairs on their pereiopods, or walking legs, also aid in detecting food on the bottom.
Once food is located, prawns use several feeding appendages for manipulation and ingestion. Maxillipeds, specialized mouthparts, help manipulate food and hold larger particles. Mandibles bite, tear, and crush food into smaller pieces. Other structures like the maxillae, paragnaths, and labrum coordinate to maneuver food into the esophagus. Prawns also use their chelated pereiopods to collect food particles from sediment, passing them to the mouthparts.
Variations in Prawn Diet
A prawn’s diet varies based on its life stage, habitat, and food availability. Larval prawns, such as nauplii, initially rely on yolk reserves. As they develop into protozoeal stages, they become nonselective filter-feeders, consuming phytoplankton and small zooplankton. During the mysis stage, they transition to active predation on larger zooplankton, while juveniles and adults adopt a broader omnivorous diet. Protein requirements also change, with post-larval stages needing a high protein diet (40-55%) for rapid growth.
Differences in habitat also influence dietary composition. Freshwater prawns primarily feed on biofilm, algae, and decaying plant matter in rivers and streams. Saltwater species have access to a wider array of food sources, including marine algae, plankton, and the remains of other sea creatures. The specific environment directly impacts available food items. While generally omnivorous, some species exhibit preferences, such as certain Macrobrachium species preferring plant material compared to more carnivorous Penaeus species.