Identification and Expression Profile of a Neuropeptide LFRFamide-Like Gene During Different Stages of Gonadal Development in the Cephalopod Sepia pharaonis

Neuropeptides are widely distributed in vertebrates and invertebrates,regulating a variety of physiological activities in the organisms,such as metabolism,feeding and reproduction.In this study,to explore the function of neuropeptide LFRFamide in Sepia pharaonis,the full-length cDNA of LFRFamide-like gene(named SpLFRFL,MG869822.1)was identified with rapid amplification of cDNA ends(RACE)method.The sequence of SpLFRFL was 860 bp in length and encoded 188 amino acids containing 4 different mature peptides:1 copy of PHTPFRFamide,NSLFRFamide,TIFRFamide,and 3 copies of GNLFRFamide.Multiple alignment and phylogenetic analysis results showed that SpLFRFL shared high identity with LFRFamides of Sepia officinalis and Sepiella japonica and had the closest relationship with them.Through quantitative Real-time PCR(qRT-PCR),it was found that the SpLFRFL gene was highly expressed in the optic lobe and brain at three different stages during gonad development in both genders.Moreover,the four mature peptides at a concentration of 0.01μmol L^(−1) could inhibit the protein synthesis in the Chinese hamster ovary cell strain-K1(CHOK1)induced by SpGnRH.These data suggest that SpLFRFL might be involved in the development and reproduction of S.pharaonis.The results can contribute to future studies on neuropeptide evolution and function and benefit the cuttlefish farming.

Physiological and Molecular Analyses of Low-Salinity Stress Response in the Cuttlefish(Sepia pharaonis)Juveniles

As a stenohaline species,the survival of Sepia pharaonis can be affected by salinity significantly.This study aimed to explore the function of decreasing salinity on the survival of Sepia pharaonis,which can provide an advanced production guide on the culture of S.pharaonis in the rainy season.Salinity was gradually decreased from 29 to 22 within 48 h to acclimate S.pharaonis to a low-salinity environment.After ten days of breeding under low-salinity of 22,the death rate was high.In this process,changes in tissue and cell structures in the larval liver,biochemical indicators,and osmoregulation-related gene expression were examined.In-terestingly,hepatocytes in the low-salinity group were irregular,had dissolved tissue inclusions,and contained vacuolized cells.There-fore,low salinity caused severe damages at a cellular level that can elevate the mortality rate.A gradual decline in salinity limited the full adaptation of S.pharaonis.Biochemical indicators and osmoregulation-related gene expression changed similarly.For instance,the trend of malondialdehyde(MAD)as a product of lipid peroxidation reflected the degree of damage to the body by free radicals.The antioxidant system of S.pharaonis could cope with oxidative stress caused by the change in salinity to a certain extent.Osmo-regulation-related genes’expression also showed an optimistic result,that is,S.pharaonis responded positively to the change in sali-nity by adjusting the expression of osmoregulation-related genes.Conversely,the increase in mortality at day 10 also proved the weak adaptation capability of S.pharaonis.This study indicated that S.pharaonis can adapt to a low-salinity environment with a li-mited extent.