Spermatogenesis Of Different Ploid (Oncorhynchus Mykiss) Rainbow Trout

Because of the tasty meat and rich nutrition, rainbow trout had become one of three recommended cultural fish by the world food and farming organization, and aslo the important cold-water cultivated fish in china. Since polyploid induction technique has become widespread, especially in rainbow trout artifical-induced polyploidy fish had been successfully produced. Female triploid rainbow trout had a much stronger growth advantage and population yields owning to the agenesis of gonad compared with the diploid conterparts. Recently, artifical-induced triploid sterile lines had become commercial used. In accordance with the production of triploid fish, tetraploid rainbow trout had been successful induced.Our experiments were carried out used the different polidy rainbow trout (diploid, triploid, tetraploid) as materials, and comparative studies about the the structure of spermary and spermatogenesis of them followed the methods of histology, scanning electron microscope, transmission electron microscope. And further discussed the phenomenon of abortion, ploidy of spermatozoon, mechanisms of spermiogenesis of triploid rainbow trout during the process of spermiogenesis.The results showed that :1. Rainbow trout was typically ampulla type spermary, spermary was consisted of two parts which was outer membrance and substance part, septum was streched out from outer membrance and divided the spermary into round or long circular pars ampullaris (testicular lobules), and this pars ampullaris was full of the inside of spermary irregularly. Septum had blood vessel which could transfer nutrition and hormone through blood circulation to promote the genesis of sperm. Every testicular lobule could form spermatogonial cysts in which sperm was produced. As the maturation of sperm, spermatogonial cysts was rupture and sperm was released and converged with the lumen of lobule, at last got into the spermatic duct. Triploid male rainbow trout had fewer sperm than diploid conterparts, and the interval of lobule was filled with bulks of light-stained connective tissues, zone of necrosis emerged in lobule and was dark-stained, cells of necrosis adherenced together and were mostly abortive spermatid.2. Spermatogenesis of different ploidy rainbow trout (diploid, triploid, tetraploid) had all undergone spermatogonium, primary spermatocyte, secondary, spermatocyte, spermatid, and finally transformed into sperm. Ultrastructural organization of spermatogenic cells of different ploidy rainbow trout was the same on the whole besides the differences of volume.3. Abortion of reproductive cell of triploid rainbow trout during spermatogenesis was existed all the time, and showed various kinds of abnormity, such as the liquefaction of spermatocyte, abnormality meiosis, many spermatid tend to be disintegrate, unable to from normal sperm etc. And this phenomenon was especially obvious during the stage of spermatid metamorphosis.4. Heads of diploid rainbow trout were uniform at the size, and the volume was 3.36±0.19μm3. While,sperm of triploid rainbow trout had three types of big,middle and small, the small type of sperm accounted 29.4% of total sperm and resembled diploid rainbow trout at the volume (3.51±0.17μm3); middle type sperm with the volume (5.22±0.21μm3) of 1.56 times of haploid sperm accounted 58.8% of total sperm; big type sperm with the volume (6.87±0.19μm3) of 2.08 times of haploid sperm accounted 11.8% of total sperm. We could infer from this, the sperm of triploid rainbow trout existed three types of n type, 1.5n type and 2n type. Teraploid rainbow trout could finish spermatogenesis smoothly, the size of sperm was uniform and diameter of nucleus of head was 2.82±0.17μm.5. Based on triploid rainbow trout had n type, 1.5n type and 2n type. Sperm, we could specula- te that most spermatocyte of triploid rainbow trout could finish meiosis and form 1.5n type sperm; parts of spermatocyte undergo disparity division, forming sixty bivalent and sixty univalent, that is n type and 2n type sperm. another parts of spermatocyte happened derangement of synapsis, could not finish meiosis and ultimitaly leaded to cellular necrosis.6. Sertoli cell plays as a role of supporting, fixing and conveying nutrition for reproductive cell in spermary of triploid rainbow trout, and similarly had the function of secretion. Sertoli cells surounded the abortive reproductive cells were hypertrophy, and cytoplasm of them had many lysosomes which could phagocytize abortive spermatogenic cells.