中国鲎2龄稚鲎不同光照周期下摄食节律变化及消化道排空率研究OA

To investigate the effects of photoperiod on the feeding rhythms and gastrointestinal evacuation dynamics of second-instar juvenile Tachypleus tridentatus,this study examined diel feeding rhythms in second-instar juvenile T.tridentatus using eight observation time points over 24h under three photoperiod regimes:natural photoperiod,constant light,and constant darkness.Feeding rhythms were assessed via gastrointestinal satiety indices,and evacuation dyna-mics were tracked for 24h after satiation.The results showed that there were no significant differences in average satie-ty among time points within any photoperiod at 3h or 6h post-feeding.Under natural photoperiod at 3h,satiety was significantly higher at night than during the day,whereas no clear diel differences were observed under continuous light or darkness.By contrast,at 6h post-feeding,satiety indices were consistently higher at night than during the day under all three photoperiods.Feeding peaks under the natural photoperiod at 3h post-feeding occurred during the night-time period(21:00-06:00),while no distinct diel feeding rhythm was detected under continuous light or darkness.However,at 6h post-feeding,clear feeding rhythms emerged under both continuous light and continuous darkness,with feeding peaks occurring at 21:00-09:00,and 21:00-06:00,respectively.Most juveniles achieved substantial food intake within 3h,with only marginal increases observed by 6h.Gastrointestinal evacuation exhibited a biphasic pattern characterized by an initial rapid phase followed by a slower phase.First-time feeding juveniles reached 50%evacua-tion at 14.7h and 80%at 27.1h after satiation,whereas non-first-time feeding juveniles reached the same benchmarks at 8.8h and 16.3h,respectively.These findings demonstrate that second-instar juvenile T.tridentatus exhibit a pronounced diel feeding rhythm,only weakly influenced by photoperiod.Based on these results,it is recommended that juvenile rearing be conducted under a natural photoperiod with at least one feeding event after dusk and moderately extended during the early feeding stage.This study provides a scientific basis for optimizing feeding strategies in the artificial culture of juvenile T.tridentatus.