Abstract
Diurnal rhythms in egg laying and hatching of the skin fluke Neobenedenia girellae were investigated under different light conditions. Egg production was monitored every 2 h for 3 days under two light conditions (darkness and natural light) using Seriola dumerili infected with multiple N. girellae as well as black molly Poecilia sphenops that had been transplanted by a single mature fluke. In any cases, oviposition was continuously observed with no obvious diurnal rhythm. The maximum egg production was approximately 60 eggs/h/worm for both multiple- and single-infection. Such high fecundity emphasizes the importance of the prompt eradication of mature flukes from culture sites to prevent parasite multiplication. The hatching rhythm was monitored under natural light condition and controlled light condition with LED lamp (24L, 12L:12D, 24D). An obvious hatching rhythm with a monomodal peak in the morning was detected under natural light condition. This rhythm was different from that previously reported for Benedenia seriolae whose hatching has bimodal peaks in the early morning and evening. Under controlled light conditions, no such pattern was observed and the overall hatching was considerably less than that under natural light condition.
