Activity of some of the main enzymes involved in protein digestion and absorption (acid and alkaline proteases, leucine‐aminopeptidase, acid and alkaline phosphatases) as well as those of amylase and lipase, was assessed during larval development of white sea bream Diplodus sargus. All enzyme activity was detected at the moment of mouth opening. The variations observed in the activity profiles of the digestive enzymes were correlated either to developmental events, such as the functional start of the stomach (22 days after hatching), or to changes in the nature of the diet. The early and noticeable development of digestive enzyme activities was linked to a high survival after weaning.

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There has been considerable discussion in recent years on the evolution of the tandemly repeated multigene families, since some organisms show a concerted model whereas others show a birth-and-death model. This controversial subject extends to several species of fish. In this study, three species of the Sparidae family (Pagrus pagrus, P. auriga and Diplodus sargus) and an interspecific hybrid (P. pagrus (♀) × P. auriga (♂)) have been studied at both molecular and cytogenetic level, taking three different multigene families (5S rDNA, 45S rDNA and U2 snDNA). Results obtained with the 5S rDNA in P. pagrus and P. auriga are characterized by a considerable degree of conservation at the two levels; however, an extraordinary variation was observed in D. sargus at the two levels, which has never been found in other fishes studied to date. As a consequence of this, the evolutionary model of the multigene families is discussed considering the results obtained and others from the bibliography. The result obtained in the hybrid allowed the recombination frequency in each multigene family to be estimated.