Effect of the incubation temperature on the embryonic development and hatching time of eggs of the red porgy Pagrus pagrus (Linne, 1758)(Pisces: Sparidae)

Abstract

Assessment of egg quality at early embryonic stages may be useful predictive criterion to evaluate the potential mass juvenile production in red porgy Pagrus pagrus. The objective of the present study is to describe in detail the embryonic developmental stages in the red porgy and the time taken by larvae to hatch at three incubation temperatures. Fertilized eggs obtained from natural spawnings were incubated at 15, 20 and 25°C. Photomicrographs of all the embryonic stages were taken at the three temperatures. Cell divisions after fertilization and organ appearance during the embryonic development were identified. The sequence in cellular divisions and appearance of sensory and motor organs were the same for the three temperatures, although the higher the temperature, the faster the stages of development. Hatching time was also determined by the incubation temperature. At 25°C the completely-formed embryo hatched at approximately 25 h 26 min after fertilization whereas at 20°C and 15°C hatching occurred 37 and 60 h post fertilization. Knowledge of the normal embryonic stages, the sequence of cleavages, the egg diameter, the number of oil drops, the timing of organ formation and the hatching rate is a basic requirement for assessing the eggs batches quality during seed mass production.