Qinba Mountain Onychostoma Macrolepis’s Morphology, Histology Characteristics And Its Circadian Clock Genes Expression

Onychostoma macrolepis,a kind of precious wild endangered species,is Chinese native fish with high species diversity,dominanting the Shaanxi Qinba Mountains fish population.O.macrolepis have unique living habit,which known as “wintering in cave springs”,a kind of hibernation.It is in the period of hibernations from October to next March that O.macrolepis lives in the dark cave springs while the other months are in the period of non-hibernation,which means that O.macrolepis lives in the dark cave environment for nearly a half of year.In the present study,the O.macrolepis’ s adaptability to hibernation were investigated based on the results from traditional morphometry,histology and qRT-PCR.The study was carried out in March(later period of hibernation),June(breeding period),October(early period of hibernation)and the next January(mid period of hibernation).The results are as follows:(1)The growth and development of 1,2,3-year-old breeding O.macrolepis showed nonlinear growth;As troglophile cave fish,the relative values of Body height,Eye diameter and Caudal peduncle height decreased during the hibernation.(2)The histological structures of the heart,liver,spleen,kidney,intestine,testis and ovary of adult O.macrolepis showed differences between the hibernation and breeding season,but no significant changes were found in the gills.(3)The identity of 6 circadian clock genes of adult O.macrolepis were all close to zebrafish.They were detected to be expressed in all tissues.The expression level was significantly different in the hibernation and breeding periods.(4)The homologous isoforms of cipc and cry1 showed different expression levels in the same organ at the same period.The discrepancy trend changed with the month.And in March,June and October,the expression level of two homologous isdoforms showed opposite comparative results.Therefore,the present study indicate that O.macrolepis’ morphology,histology characteristics and its circadian clock genes expression level showed significant changes between hibernation and breeding period.