Protein metabolism, growth and pigmentation patterns during metamorphosis of plaice (Pleuronectes platessa) larvae

Abstract

Protein metabolism, growth and pigmentation patterns were studied during the process of metamorphosis in the plaice Pleuronectes platessa. Based on the morphological and concurrent metabolic observations the process of metamorphosis could be divided into three different phases: (1) premetamorphosis: from hatching to beginning of eye migration, (2) climaxmetamorphosis: eye migration, and (3) postmetamorphosis: the period immediately after completion of eye migration. During premetamorphosis a gradual increase in DW was observed concomitant with constant concentrations of the nucleic acids RNA and DNA of the larvae. An increasing calcium concentration indicated the beginning of skeleton ossification. Growth during this phase was primarily hyperplastic as indicated by an increase in DNA per larva. Protein catabolism dominated, as indicated by an increase in the carbon to nitrogen ratio concomitant with a decrease in nitrogen per unit DW. During climaxmetamorphosis an initial increase in the concentration of RNA was followed by a decrease in RNA, DNA and protein concentrations and the ratio of RNA to DNA. During postmetamorphosis growth of the larvae was again observed to be hyperplastic. Calcium assimilation reached a plateau depicting complete ossification of the skeleton. Lipid catabolism dominated by the end of the metamorphosis process. Pigmentation appeared to develop in two marked phases. During premetamorphosis larval melanophores and xanthophores dominated the pigmentation pattern. The concentration of these chromatophores was markedly reduced at beginning of the eye migration process. During and immediately after eye migration the concentration of chromatophores increased significantly and the melanophores appeared to be of the adult type.