Effect of Low Environmental Temperature on Embryonic Development and Egg Hatching of Diplectanum aequans (Monogenea, Diplectanidae) Infecting European Sea Bass, Dicentrarchus labrax.

The effect of low incubation temperature on the embryonic development and larval hatching of the monogenean Diplectanum aequans, a gill parasite of sea bass Dicentrarchus Iabrax, was studied. Groups of eggs of D. aequans were incubated at 5°C for different time periods (from 24 h to 28 days) before incubation at room temperature (18°C). Percentages of hatched larvae, aborted larvae and undeveloped embryos were estimated in comparison with the control group. Results show that eggs of the parasite are able to survive at 5°C, with a percentage that decreases as the incubation time at 5°C increases, reducing the rate of larval hatching.