Killing effects of various treatments on eggs of the skin-parasitic monogeneans Neobenedenia girellae and Benedenia seriolae

The effects of heat (40, 50 and 60 °C), drying, freshwater, benzalkonium chloride (100 ppm) and chlorine (60 and 120 ppm available chlorine concentrations) treatments on the hatching abilities of Neobenedenia girellae and Benedenia seriolae eggs were studied. The eyeing and hatching rates of N. girellae and B. seriolae eggs heated at 50 and 60 °C for 1, 5 and 10 min; dried for 1 and 24 h; and treated with 120 ppm available chlorine concentration for 24 h were 0%. The eyeing and hatching rates of the eggs of both parasite species treated with freshwater, 100 ppm benzalkonium chloride and 60 ppm available chlorine concentration for 24 h were lower than those of controls (P < .05), but hatching was not prevented completely except in N. girellae eggs treated with 60 ppm available chlorine concentration for 24 h. In contrast, N. girellae eggs treated with 40 °C for 10, 30 and 60 min were not affected, although the hatching rates of B. seriolae eggs of these treatments were lower than those of the controls (P < .05). In addition, the eggs of these parasite species were not affected by freshwater, 100 ppm benzalkonium chloride, or 60 and 120 ppm available chlorine concentrations for 1 h. The results of this study may be useful for preventing horizontal infection with these parasites from used equipment and tanks in fish-rearing facilities.