| 1 | Changes in embryonic development,juvenile growth and physiological adaptation of the cuttlefish Sepia pharaonis in response to photoperiod manipulation显示文摘Photoperiod is a key environmental indicator for re gulating embryonic development,individual growth and physiological processes in aquatic animals.In this study,differences in embryonic development and performance of newly hatched cuttlefish juvenile exposed to five different cycles of light:dark(L:D):constant light,18 L:6D,12 L:12D,6 L:18D cycles,and constant darkness were evaluated.Prolonged exposure to light induced an accelerated rate of embryonic development,particularly after the red-bead stage.Principal component analysis(PCA)revealed that red-bead stage,heartbeat,endoskeleton formation,pigment appear,and six increments of cuttlebone were the main factors contributing to the embryonic development.Meaning that the duration time of these five stages were significantly different when exposed to photoperiod regimes,which may determine the duration of the incubation period of the embryos.Long term light has also affected the incubation parameters with an increased rate in hatching and shortened the incubation and hatching periods in the 12-24-h day length range.However,constant light and darkness environment appeared to have a greater effect on the stress of embryonic development,mainly reflected in the yolk shed ratio and the inking rate in the egg capsule.Moreover,the increase in the day length has contributed to improve the growth and survival of juveniles in the 12-18-h day length range;however,juveniles exposed to constant light and darkness experienced worse re sults in terms of growth,tissue glycogen content,dige stive enzymes of the digestive glands,and metabolic enzymes of the muscles.These finding suggest that prolonged light exposure accelerates the process of embryonic development,maximum feeding time is not necessarily a condition of optimal growth,and inappropriate light cycles can disturb the body’s endogenous controls.Therefore,the optimal photoperiod for the embryos development and juvenile growth of Sepia pharaonis were 12 h and 12-18 h of day length,respectively.These results are useful for increasing the production of this species during embryo incubation and juveniles rearing in aquaculture practice. | Maowang JIANG Huan CHEN Shuangnan ZHOU Qingxi HAN Ruibing PENG Xiamin JIANG | 2022 | Journal of Oceanology and Limnology2022，40，5： | 0 |
| 2 | Effects of Different Weaning Protocols on Survival,Growth and Nutritional Composition of Pharaoh Cuttlefish(Sepia pharaonis)Juvenile显示文摘The aim of this study was to determine the optimal weaning protocols for rearing juvenile cuttlefish Sepia pharaonis,as well as to understand the feeding habits of cuttlefish and develop effective aqua-cultural practices.The effects of four experimental weaning protocols(i.e.,food type,cuttlefish size,food ration(bw d^−1)and feeding frequency(meals d^−1))on the growth,survival and muscle proximate composition of cuttlefish juvenile were studied in quintuplicate.The weaning period lasted 2 weeks.The results showed that cuttlefish fed with frozen white shrimp(Exopalaemon carinicauda)displayed a significantly higher survival,growth parameters,ingestion rate,food conversion rate,and muscle protein content when compared with the other prepared frozen foods.The larger individuals revealed better growth performance than smaller individuals,especially in terms of survival and specific growth rate,indicating that larger individuals were more receptive to frozen prey.Furthermore,size grading should be conducted to ensure better growth during weaning.As food rations increased,the survival,growth and muscle protein content of juveniles were promoted,whereas the most appropriate food ration for cuttlefish juvenile was 35%bw d^−1.Similarly,higher feeding frequency could stimulate the appetite of animals reared on weaning,and enhance survival,growth,and protein deposition compared to low feeding frequency.These results suggest that the optimal feeding protocols of juvenile weaning is as follows:the ideal prepared food is frozen shrimp,the weight of juveniles should be 4.0 g(32 days old)or more,the food ration should be 35%(bw d^−1),and the optimum feeding frequency is 4 meals day^-1.This study offers a promising starting point to successfully breed this candidate aquaculture species. | JIANG Maowang HAN Ziru SHENG Peng PENG Ruibing HAN Qingxi JIANG Xiamin | 2020 | Journal of Ocean University of China2020，19，6： | 0 |
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