Study by evolution of nucleic acid content of prepuberal growth in the shrimp Crangon vulgaris

Growth of the shrimp Crangon vulgaris was studied by following the evolution of its nucleic acid concentration and total content. Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) analysis were effected on homogenates of whole shrimps. Cell multiplication was estimated from evolution of total DNA content, and cell size increment from evolution of fresh weight: DNA ratio. DNA puric bases ratio and RNA monoribonucleotides percentages were constant throughout the investigation period. A decrease in DNA concentration was observed from 50 to 20 M/g dry defatted weight (DDP), when fresh weight increases from 40 to 570 mg. This decrease was more marked in the first half of the period studied (prepuberal phase). The DNA content in the whole shrimp increases with fresh weight without slowing down at sexual maturity. However, at the beginning of the prepuberal phase the cell-multiplication rate seems to be graduated rather than continuous; this is still to be explained. Cell size, calculated from fresh weight: DNA ratio, increases until the shrimp weighs 300 mg; beyond this weight, cell increment proceeds much more slowly. The weight gain of shrimps throughout the growth period studied is mainly attributable to hyperplasia — which occurs constantly — while hypertrophy insures only 21% weight increment in the largest shrimps. As protein content, RNA content is a linear function of shrimp weight. RNA:DNA ratio evolution is similar to that of cell size and protein content. We suggest that cells have attained a physiological balance when shrimps reach a weight of 300 mg.