| Reproduction is an important part of the life cycle in fish.In this paper,in order to understand the reproduction rules and strategies,and enrich the reproduction biology information of Eleutheronema tetradactylum,it provides necessary theoretical reference for the protection,development,utilization and the improvement of artificial breeding techniques of E.tetradactylum.We conducted a preliminary study on the testis development,ovary development,spermatogenesis,oogenesis,sex reversal of E.tetradactylum from the aspects of morphology,histology and cytology,and the main results are as follows:1.Studies on the developing testes and spermatogenesis in Eleutheronema tetradactylumIn this study,in order to understand the process of the testis development and spermatogenesis in E.tetradactylum,paraffin tissue sections were used to observe the developmental process of testes via haematoxylin-eosin(HE)staining and transmission electron microscopy(TEM)in order to understand the organizational structure of the testes as well as the histological and ultrastructural changes associated with spermatogenesis during primary sexual maturity in cultured fourfinger threadfin individuals.The results showed that the testes were a pair of extended flat zonal organs that were gray in color and fused at the posterior end into a Y-shape.The organs were located on the dorsal side of the abdominal cavity,attached to the ventral surface of the mesonephros and swim bladder.The developmental process of the testes was divided into six stages defined by histological characteristics.The testes develop to stage I(spermatogonia proliferates),followed by stage II(spermatocyte growth),stage III(spermatocytes mature),and stage IV(sperm begin to appear)at about three months of age,four months of age,five to seven months of age,and seven to nine months of age,respectively.At a minimum of 10 months of age,the testes develop to stage V(complete maturation of sperm)and reach the first stage of sexual maturity.The post-reproductive testes in stage VI(degradation and absorption)were observable after the breeding season.Spermatogenesis went through six phases,namely primary spermatogonia,secondary spermatogonia,primary spermatocyte,secondary spermatocyte,spermatocyte,and sperm in succession.The diameter of cells and nuclei decreased step by step,and the ratio of nucleus to cytoplasm changed regularly.During spermatogenesis,chromosomes in the nucleus were gradually condensed,electron density was increased,and mitochondria were enlarged and aggregated with an inner cristae structure that was gradually enriched.Sperm was composed of a head,middle,and tail.The axial filament of the flagella followed a typical “9+2” structure.2.Studies on the developing ovary and oogenesis in Eleutheronema tetradactylumIn this study,in order to understand the process of the ovary development and oogenesis in E.tetradactylum,tissue section with H-E staining technique was used to observe the changes of tissue structure in ovary development and the structure of oocytes in different phases during oogenesis.The results showed that it was a membrane-type ovary,close to the abdominal surface of the middle kidney,and the two ovaries were separated at the front end and fused at the back end,presenting a "Y" shape.The oogenesis process can be divided into five phases,from the oogonium with diameter of 6.60?40.86 ?m developed into the mature eggs with the diameter of 348.02?462.84 ?m gradually.Fewer follicular cells began to appear around the oocytes in medium phase II,monolayer follicular cells were formed in the later phase II,monolayer thecal cells was formed at medium phase III.The yolk nucleus began to appear at the middle phase II and disappeared at the early phase III.The yolk vesicle appeared near the nucleus and cytoplasmic margin at the early phase III.The yolk granules began to appear between the yolk vesicles at the late phase III,and filled the yolk vesicles at the early phase IV,and formed the yolk lamellae at the late phase IV.During the process of ovary development,each stage has different phase of oocytes.At stage V,the oocytes diameter showed a bimodal distribution,with peaks in the range of 50.00 ? 100.00 ?m and 300.00 ? 350.00 ?m,respectively.According to the above characteristics,the development pattern of the ovary is asynchronous development-batch spawning type.3.Studies on the sex reversal in Eleutheronema tetradactylumIn this study,in order to understand the breeding strategy of the E.tetradactylum,morphological and sex ratio statistics of the population in circulating culture were carried out,and their gonads were observed with morphological and histological methods.The results showed that,under the conditions of culture salinity is 10.8?13.0 and water temperature is 28.0?30.7 ?,three kinds of male,female and hermaphrodite were detected in the 228 samples at the age of 7 months,which were 85.53 %,5.70 % and 8.77 %,respectively.And there was no significant difference in body weight,total length,body length and body height of each species.The correlation fitting curve equation between the body weight and total length,body length,body height of the hermaphrodite were y = 0.6568x2-12.431 + 56.718(R2= 0.9164),y =0.0147x3.0755(R2=0.8698)and y = 2.0054x2.6029(R2=0.8333),respectively.Anatomic observation showed that the two dorsolateral sides of the androgynous gonads are testis with white,and the two ventrolateral sides were ovaries,which were yellowish and reddish.Histology showed that mature sperm had formed on the testis side,which was the stage IV or V feature of typical testis,and the ovary side had an ovarian cavity,oogonium and early 2 phase oocytes mainly,which was the stage II feature of typical ovary.And this is typical feature of protandrous hermaphrodites.The process of sex reversal can be divided into three stages: early,middle and late.The main feature of tissue structure change is that the testis structure gradually degenerates and disappears,while the ovary structure gradually forms and develops into stage II ovary.The apoptotic cell signal of the testis is detected during the whole sex reversal process. |
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