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 l arval hatching of the monogenean Diplectanum aequans, a gill parasite of se a bass Dicentrarchus labrax, was studied. Groups of eggs of D. aequans were incubated at 5 degreesC for different time periods (from 24 h to 28 days) before incubation at room temperature (18 degreesC). Percentages of hatched larvae, aborted larvae and undeveloped embryos were estimated in compariso n with the control group. Results show that eggs of the parasite are able t o survive at 5 degreesC, with a percentage that decreases as the incubation time at 5 degreesC increases, reducing the rate of larval hatching.