Croissance larvaire contrôlée de Penaeus japonicus Bate. Enzymes digestives et changements de régimes alimentaires

The larval and postlarval development of the shrimp Penaeus japoniaus has been stu­died on the basis of the evolution of nucleic acids, of proteinic compounds, and of digestive enzymes. Cell multiplication was assayed by tracing the evolution of the amount of desoxyribo­nucleic acid (DNA) ; this multiplication was found to be high during nauplius stages. Evolu­tion in time of ribonucleic acid (RNA) was compared with evolution of dry weight and proteins ; the amount of RNA rises considerably during stage zoe. Thus it is thought that during stages nauplius and mysis, cellular hyperplasy takes place, while cellular hypertrophy would aarac- terize stage zoe. The development of a new stock of digestive enzymes takes place during the zoe sta­ge. The variations of amylasia (A) and proteasia (P) activities as well as their ratio (A/P), tend to show that the diet is predominantly based on glucids at the end of the zoea stage and at the beginning of the mysis one. The shrimps become more carnivorous later on.