Effects of temperature, salinity, desiccation and chemical treatments on egg embryonation and hatching success of Benedenia seriolae (Monogenea: Capsalidae), a parasite of farmed Seriola spp.

The effects of temperature and salinity on the embryonation period and hatching success of eggs of Benedenia seriolae were investigated. Temperature strongly influenced embryonation period; eggs first hatched 5 days after laying at 28 °C and 16 days after laying at 14 °C. The relationship between temperature and embryonation period is described by quadratic regression equations for time to first and last hatching. Hatching success was >70% for B. seriolae eggs incubated at temperatures from 14 to 28 °C. However, no B. seriolae eggs embryonated and hatched at 30 °C and <2% of eggs hatched when incubated at 24 °C after transfer to 30 °C for 48 h. Embryonation period was similar for eggs incubated in sea water at 25, 30 and 35‰ salinity, but increased for eggs incubated at higher or lower salinities. When incubated at salinities ranging from 25 to 45‰, more than 70% of B. seriolae eggs embryonated and hatched. Hatching success was lower at 20 and 50‰ salinity and few or no eggs hatched at 10 and 15‰. Hatching of B. seriolae eggs can be prevented by desiccation for 3 min, by immersion in water at 50 °C for 30 s or by treatment with 25% ethanol for 3 min.