AbstractLarvae of two caridean shrimp species,Macrobrachium rosenbergii(De Man) andPalaemon elegansRathke, were fed live and artificial diets.P. eleganslarvae fed exclusively liveArtemia salina(15 nauplii mL−1) developed into first postlarval stage (PL1) within 12 days at a temperature of 25°C and salinity 32.5 g L−1. Their survival and mean total length at this stage were 88.5% and 6.7 mm respectively.M. rosenbergiilarvae fed on 15ArtemiamL−1started to metamorphose into PLl within 24 days at 29–30°C and 12 g L−1. Attempts to completely replace liveArtemiafor rearingP. elegansduring early stages failed, and only a partial replacement was achieved for the larvae of both species.P. eleganslarvae survived (49%) solely on a microgranulated diet (Frippak PL diet) from stage zoea (Z) 4–5 to PL1. Similarly, a microencapsulated diet (Frippak CD3) also sustainedM. rosenbergiilarvae from Z5–6 to PL1 with a 28% survival. Development of the larvae of both species was retarded by 2–3 days and their survivals were lower than those fed on the live diet.The inability of the early larvae of these caridean species to survive on artificial diets is attributed to their undeveloped guts and limited enzymatic capabilities. Trypsin activity in the larvae was determined for all larval stages. It was found that the highest trypsin activity, at stage Z4–5 inP. elegansand at stage Z5–6 inM. rosenbergii, coincides with a rapid increase in the volume of the hepatopancreas and the formation of the filter apparatus. These morphological changes in the gut structure appear to enable the larvae to utilize artificial diets after stage Z5–6. Low larval trypsin activities may be compensated by the easily digestible content of their live prey during early larval stages (Z1–Z4/5) and by longer gastroevacuation time (GET) and almost fully developed