The shrimp nauplius is a nonfeeding, planktonic stage (Rothlisberg, 1998). The three shrimp protozoea stages are nonselective filter-feeders (Rothlisberg, 1998; Narciso and Morais, 2001) that feed mostly on phytoplankton and small zooplankton like rotifers. From mysis through to postlarva (PL), there is a transition to active predation on larger zooplankton (Lovett and Felder, 1990) (Table 1).
Juvenile P. monodon are fairly carnivorous (Tacon, 2002), feeding on seaweed, algae, crustaceans, detritus (bacterial colonies), molluscs and fish parts (Hall, 1962; FAO, 1968b; Marte, 1980; El Hag, 1984; Sultana, 2000). El Hag (1984) found that adults feed on crustaceans, annelids, algae and mud (Table 1).
Digestive system
Penaeid shrimp have a morphologically typical decapod digestive tract (Dall et al., 1990). Detection of feed begins with sight and touch, but shrimp also have numerous chemoreceptors on their appendages (e.g. the mandible, maxillule, maxilla, lateral antennular flagellum, dactyls of maxilliped 3 and periopods, merus of periopods, maxillipeds and the branchial chamber) (Lee and Meyers, 1997). The digestive tract of shrimp is divided into three main parts, the foregut, midgut and hindgut (Ceccaldi, 1997). The foregut (proventriculus, stomach) comprises the oesophagus and the part of the stomach where mastication occurs. The midgut gland or hepatopancreas (Figure 13) secretes digestive enzymes, absorbs digested products and maintains mineral reserves. It also functions in lipid and carbohydrate metabolism, the distribution of stored reserves and the catabolism of some organic compounds (Ceccaldi, 1997).
