Mating behaviors in ovoviviparous black rockfish(Sebastes schlegelii):molecular function of prostaglandin E2 as both a hormone and pheromone

Prostaglandins(PGs)are profound hormones in teleost sexual behavior,especially in mating.PGs act as pheromones that affect the olfactory sensory neurons of males,inducing the initiation of a series of mating behaviors.However,the molecular mechanism by which PGs trigger mating behavior in ovoviviparous teleosts is still unclear.In the present study,we employed the ovoviviparous black rockfish(Sebastes schlegelii),an economically important marine species whose reproductive production is limited by incomplete fertilization,as a model species.The results showed that when the dose of PGE2 was higher than 10 nmol/L,a significant(P<0.05)increase in mating behaviors was observed.Dual-fluorescence in situ hybridization indicated that PGE2 could fire specific neurons in different brain regions and receptor cells in the olfactory sac.After combining with specific neurons in the central nervous system(CNS),a series of genes related to reproduction are activated.The intracerebroventricular administration of PGE_(2) significantly increased lhb levels(P<0.05)in both sexes.Moreover,steroidogenesis in gonads was also affected,inducing an increase(P<0.05)in E_(2) levels in males and T levels in females.PGE_(2) levels were also increased significantly(P<0.05)in both sexes.The present study revealed that PGE2 can activate mating behavior in black rockfish in both hormone and pheromone pathways,leading to variations in sex steroid levels and activation of reproductive behaviors.Our results provide not only novel insight into the onset of mating behaviors in ovoviviparous teleosts but also solutions for the incomplete fertilization caused by natural mating in cage aquaculture.

Molecular characterization and expression patterns of nuclear androgen receptors in the ovoviviparous black rockfish Sebastes schlegelii

nARs are ligand-activated transcription factors associated with gonadal development and reproductive regulation.In this study,two nuclear androgen receptor genes(ara and arb)were cloned from an ovoviviparous teleost,black rockfish(Sebastes schlegelii).The phylogenetic analysis of nARs showed that nARαand nARβclustered into teleost nARαand nARβ,respectively,but differed from the nARs of tetrapods.Four module domains of the nuclear receptor superfamily are present in the black rockfish nARs,an N-terminal domain(NTD),a DNA-binding domain(DBD),a hinge region(HR)and a ligand-binding domain(LBD).Among the four domains,only the DBD and LBD of nARαand nARβare relatively conserved.Tissue distribution analysis revealed that ara was mainly expressed in the gonad,muscle,intestine and kidney in males and in female,while arb was mainly detected in the gonad,followed by the intestine,kidney and head kidney.During the gonadal development process,the expression levels of ara and arb were significantly decreased from the regenerating to late stages of spermatogenesis and significantly increased in the degeneration stage in the testis(P<0.05).In the ovary,the expression levels of ara and arb were not significantly different in different stages.In situ hybridization revealed that in black rockfish,both ara and arb transcripts were localized to the Sertoli cells of the testis in black rockfish.In general,the present study is the first to characterize and analyse the expression of nuclear androgen receptors,including ara and arb,in black rockfish.