The Research In Occurrence And Differentiation Of Gonads In Odontobuits Potamophila

The Odontobutis potamophila is subordinated to Perciformes, Odontobutidae. Itis an important freshwater commercial fish in China. As far as we known, the biology,embryonic development and organ development of the Odontobutis potamophila hadbeen well-studied. By observing the occurrence and differentiation of the fish gonads,we could preliminary know the morphological characteristics of early gonadaldevelopment stage. This paper provided theoretical basis for the for nurserying andartificial breeding Odontobutis potamophila. The main results are as follows:1,The occurrence of the Odontobutis potamophila gonadsParaffin-embedded section method and H.E. staining were used to study thereproductive system development. The gonad of newly hatched larvae,3days larval,6days larval,9days larval,12days juvenile,15days juvenile,18days juvenile,21days juvenile and35days juvenile Odontobutis potamophila were observed. Themain results are listed as follows: The occurrence of gonads of the Odontobutispotamophila were divided into four stages. The first stage was the newly hatchedlarvae. Average body of this stage was5.18mm, the related indications of the gonadswere not observed; the second stage was3d-12d after hatching larvae. The averagebody length was from5.56mm to7.76mm, two organization protrusions appeared inthe both side of renal tubular body cavity mold base. Primordial germ cells wereobserved to move into the prominence. The germ cell was oval-shaped, larger thanaverage germ cell. The diameter of the cell was approximately6.93μm, and theaverage nuclear diameter was1.09μm. Basophilic of cytoplasm was weak, andcoloring of nucleus was light; the third stage was12d-21d juvenile, the average bodylength was from7.76mm to9.34mm. Organization protrusions increased and thegenital ridge was emerged. The primordial germ cells PGC were about15-20in thegenital ridge, cell volume increased, and nucleus were obvious, which formed longand slender ribbon of gonadal with the genital ridge; the fourth stage was21d-35djuvenile, the average body length was from9.34mm to11.27mm, the number of the primordial germ cells were increased at this stage. Primordial germ cells developedinto germ cells, nucleus diameter was approximately4.15μm, larger and moreobvious than primordial germ cells. Gonadal primordial was significantly enlarged,and primitive gonad was basically formed.2,The ovaries differentiation of the Odontobutis potamophilaThe result of conventional paraffin sections and transmission electronmicroscopy sections showed that obvious cracks could be found in the original groupof gonadal germ cells50days after hatching, the wracks could be observed extent tothe abdominal wall on both side of the body cavity, and the ovarian cavity formed.Ovarian differentiation has been initially completed in65days, and ovarian parietalwas constituted by a thin outer layer, connective tissue, and germinal epithelium. Thespawning board had not yet formed. Ovarian cavity oogonia would develop intooocytes, which had the diameter of9.51μm and irregular arrangement. Nucleus ofoocyte became larger and obvious basophilic. Nucleus bit in the middle. Nucleardiameter was about5.14μm. Cytoplasm coloring became lighter.The connective tissues become thinner as continuous development of the ovariesincreases. The Part I oocytes was mainly observed in80-day-old ovarian slices.Oocytes were round, oval, polygonal or irregular shapes which were girdle-shapeddistributed in spawning board. Cytoplasm staining was shallow. The nucleusaccounted to about two-thirds of whole cell. Chromatin was observed intertwined andloosely distributed in nuclear that were mostly close to the nuclear membrane.1-3basophilic round deviation nucleoli could be found. A single layer of follicularmembrane could be observed round the cells which could not be stained by H.E. andtransparent by electron microscopy. The most important feature of Part I oocytes werefrequent mitosis. Mitochondria near the nuclear membrane and rough endoplasmicreticulum could be observed concentrated close to the oocyte nucleus periphery fromthe electron microscopy sections.At95days,ovarian made further differentiation, which get into small growthstages of primary oocyte growth phase. The period of oocyte was the early primaryoocytes without yolk nuclear of Part II. Oocytes tightly packed on the spawning board,cell volume increased, the shape of oocytes was irregular. Nucleus was clear, nuclearchromosomes gradually dissolved and presented to be filamentous remnants. Nucleoliincreased which was generally located in the nuclear membrane. The nuclear membrane outer edge still existed a large number of mitochondria and roughendoplasmic reticulum. Membrane outsourcing by a layer of follicular membranegradually thickened.The main features of O.potamophila ovarian differentiation was the earlyformation of a group development the oogonia group as well as the formation ofovarian cavity. Ovarian differentiation period started before testis, and ovary cavityformation is an important anatomy signs in the process of ovarian differentiation3,The testicular differentiation of the Odontobutis potamophilaParaffin sections of the testis showed that: at65days, the testis close to theperitoneum in mesentery; many primordial germ cells developed into spermatogonia.The gonads began to grow rapidly from then.Cross section of80-day-old testis slices was triangular shaped, which showedthat many large spermatogonial cells were round or slightly irregular. Nucleus wasabout5.03μm, larger than average cells. Nuclear membrane was clear with uniformnucleoplasm. Basophilic of cytoplasm was weak.2-5nucleoli could be found innucleus, often dyssymmetry. Cytoplasm staining was light; membrane was transparent.Spermatogonia form a maze-like arrangement; sseminiferous tubule formed andclusters of spermatogonia could be found.95-day-old, testis volume increased slightly, and spermatogonial cells went intoactive mitosis stage. Primary spermatocytes could be found in the testes which wasround or oval. Cells were slightly smaller than sperma togonia which was about6.15μm. Nucleus occupied a larger proportion, nuclear membrane was clear, nucleoliwas smaller, multiple, and often dyssymmetry. The nucleocytoplasmic was few andsparse-mesh-like, and light staining. Clusters of spermatogonia and primaryspermatocytes gradually formed the prototype of irregular shaped lobular, differentlobular was separated by mediation tissue.The O.potamophila testis differentiation was later than ovarian. Its principalcharacteristics included the anatomical and cellular level of differentiation, that wasthe formation of vas deferens and lobular and the emergence of the primaryspermatocytes.