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Summary
The present study describes the ontogenetic changes observed in the histology and in total protease, trypsin, and chymotrypsin activities of the digestive system in the shrimp Pleoticus muelleri (Decapoda, Penaeoidea) under culture conditions. The stomach development follows the typical pattern described for other decapods. The gland filter develops during larval stages, while the astric mill takes the adult shape during postlarval metamorphosis and juvenile stages. During early larval stages, the histological structure of the anterior and lateral caeca is similar to that of the adult midgut gland, with R, F and B cells. During late larval stages, the anterior caeca decline and take a structure similar to that of the mesodeum and the lateral caeca expand to form the adult midgut gland by proliferation of tubules in antero-posterior direction and from the cortical region to the medullar region. Total protease activity was higher in postlarvae 45, no significant differences was found in the others larval and p larval stages. Trypsin activity was lowest in early postlarval stages (PL1 and PL6), coinciding with the metamorphosis; enzyme activity increased in postlarvae 10 followed by a significant decrease in postlarvae 26. Chymotrypsin showed a significantly lower activity in protozoea 3, a peak of activity between postlarvae 1 and 10, and a decrease in the following postlarval stages. The inhibition of trypsin and chymotrypsin activities were confirmed the presence of these serine proteases during developmental stages. The ontogenetic pattern of P. muelleri digestive system morphology is similar to those described of others penaeoids. The recorded variation in enzyme activity during developmental stages may be associated with the unique postlarval life history. This research has implications for artificial diet development in crustacean culture and understanding of dietary shifts during larval development.
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