Study On Early Development Of Retina Of Eleutheronema Tetradactylum And Its Adaptation To Different Light Cycle Environments

In order to understand the early development of Eleutheronema tetradactylum(Fourfinger Threadfin)retina and the adaptability of the retina to different light cycles,In this paper,the morphological and histological methods were used to study the changes of retinal morphological structure during the early development of Fourfinger Threadfin,the histological method and transmission scanning electron microscope were used to study the retina of Fourfinger Threadfin in different light cycles,the bioinformatics analysis were used to study the nucleic acid sequence and amino acid sequence of RH1,LWS,RH2 and SWS2 of Fourfinger Threadfin and the molecular biology method were used to study the expression levels of RH1,LWS,RH2 and SWS2 in different light cycles.The main results are as follows: 1 ? Histological observation on the development of retina of Eleutheronema tetradactylum larvaeWe studied the retina structure,differentiation,forming process and visual characteristics of Fourfinger Threadfin in the early stage by paraffin serial sections,H.E staining and microscopic measurement.The main results are as follows: the retina of newly hatched larvae was not yet differentiated.Retinal pigment epithelium,outer nuclear layer,inner nuclear layer,ganglion cell layer of this species at 2 days after hatching could be clearly defined.Horizontal cells,bipolar cells and amacrine cells in inner nuclear layer of this species at 3 days after hatching had differentiated.At 4 days after hatching,the retina structure of this species was well developed.The ratio of nuclei of photoreceptor layer to ganglion cell increased from 9 days after hatching to 14 days after hatching.It indicated that convergence degree of retina was elevated and it was transition period of changes in visual characteristics.And it was adapted to ecological shift of this species.In early stage,there were only one or two layers of horizontal cells and sensitization system of this species was underdeveloped.The visual acuity of larvae in the early stage was comparatively high and vision played a very significant role in behavior and feeding and adapted to live in an adequate light environment.After they swam to shallow muddy bottoms,both the acuity and the light sensitivity were weak,therefore,vision does not had an important effect on behavior and feeding.2?Effects of different light cycles on organization structure of retina of Fourfinger ThreadfinIn this study,the changes of morphological structure and ultrastructure of the retina of Fourfinger Threadfin in different light cycles were studied by ordinary optical microscope and transmission electron microscopy.This study selected three different light cycles: 0 hour light and 24 hours dark?12 hours light and 12 hours dark?24 hours light and 0 hour dark.Fourfinger Threadfin were reared at the conditions of light intensity of(500±100)lux,water temperature 25? and salinity of 5 for 60 days.Paraffin sections and ultrathin sections of retina on the thirtieth day and the sixtieth day were made.The main results are as follows: There was no significant difference in morphological structure of the retina in different light cycles under the ordinary optical microscope.Under the transmission electron microscopy,Outer and inner segment of cones and rods in the light cycle of 0 hour light and 24 hours dark had integral and clear structure.Membrane structure of outer segment of cones and rods in the light cycle of 12 hours light and 12 hours dark on the sixtieth day were disorder and discrete lamellar structure.Under the condition of 24 hours light and 0 hour dark,membrane structure of outer segment of cones and rods were bent and outer segment were swollen on the thirtieth day and membrane structure of outer segment and ridges of mitochondrial of cones and rods were rupture.The results show that uninterrupted light will cause damage to the retina of Fourfinger Threadfin.3?Effects of different light cycles on the expression of opsin of Fourfinger Threadfin and bioinformatics analysis of opsinIn this study,the nucleic acid sequence and amino acid sequence of RH1,LWS,RH2 and SWS2 of Fourfinger Threadfin were studied by bioinformatics analysis and the expression levels of RH1,LWS,RH2 and SWS2 in different light cycles were studied by fluorescence Quantitative PCR.The results show that the open reading frame of RH1,LWS,RH2 and SWS2 opsin contained 1059 bp,1074bp,1059 bp and 1056 bp,respectively,which encoded 352,357,352,351 amino acids.And all had 7tm transmembrane domain.Fourfinger Threadfin were reared under the conditions of light intensity of(500±100)lux,water temperature 25? and salinity of 5 for 60 days.retina on the thirtieth day and the sixtieth day were frozen with liquid nitrogen and then used for fluorescence Quantitative PCR.The main results are as follows: On the thirtieth day,the expression levels of the four opsins under the conditions of 24 hours light and 0 hour dark were significantly higher than those under the conditions of 12 hours light and 12 hours dark and the conditions of 0 hour light and 24 hours dark.The significantly increased expression of opsin under the continuous light was an adaptive change.With the prolonging of rearing,the expression levels of RH1,RH2,SWS2 and LWS genes showed different changes.From the overall trend,the expression levels of RH1,RH2,SWS2 and LWS under the conditions of 12 hours light and 12 hours dark and the conditions of 0 hour light and 24 hours dark were increased.But the the expression levels were decreased under the conditions of 24 hours light and 0 hour dark.The reason may be that the change was to maintain normal circadian rhythms.