Postnatal Development Of The Male Reproductive System In Microtus Oeconomus

Microtus oeconomus attaches to Rodentia, Cricetidae, Microtinae, Microtus,and distributes in the northern part of Eurasia widely. It mainly distributes in Qinghai,Sichuan, Gansu, Ningxia and Xinjiang in China, occuping to the alpine meadow belt.The root vole habitats for the species in Qinghai haibei alpine meadow ecosystemPotentilla fruticose, herbivore and non-hibernating. According to the ecosystem trophicstructure analysis, root voles with producers (herbs) are associated with the livestockforage competition. It mainly affects crops, plantations and meadow, and is a majoragricultural endangered area of the rodents in northwest China.Based on different developmental stages of the male-vole, the morphology oftesticles, epididymis and vas deferens was studied in detail by histological methodsduring postnatal development. The effort is aimed at further identifying gonad featuresof different stages in root voles and providing scientific basis for the reproductiveecology. The results are as follows:1. Throughout postnatal development, the height of seminiferous epithelium in the rootvole testis increased obviously in 40～45d. Similarly, duct cavity diameter of theprominent changes also are concentrated in 35～50d, and the seminiferous tubulediameter changes in 35～45d obviously. Thus we can speculate that the root vole sexualmaturity is about 45 days.2. Seminiferous epithelium developed as fast as the increase of age. One day after birth,sertoli cell and spermatogonia were detected in the basal compartment. Seminiferousepithelium of 1-2 layers supported a number of sertoli cells. On the 7th days, the layerof spermatogenic epithelium was 2 mostly and spermatogonia volume increased. 11days after birth, the tubule cavity was further expanded. In addition to sertoli cell andspermatogonia, it was able to see the primary spermatocytes sparse distribution inseminiferous epithelium. The shape of sertoli cell was more diverse and spermatogenicepithelium layer was 2-3. 14 days after birth, spermatogenic epithelium distributedsertoli cell, spermatogonia and primary spermatocytes, seeing the secondaryspermatocytes and spermatids sparsely. The number of sertoli cells decreased, spermatogonia and primary spermatocytes number increased, especially in the primaryspermatocytes markedly increased. Different mitosis can be seen in primaryspermatocytes. Spermatogenic epithelium added more layers. Born after 21 days old,spermatogenic epithelium were distributed to sertoli cells, spermatogonia, primaryspermatocytes, secondary spermatocytes and spermatids. There were a large number ofsperm cells and more layers about spermatogenic epithelium. For 35 days, sertoli cellswere distributed scarcely in spermatogenic epithelium.Primary spermatocytes andsperm cells were principal. In particular, we can see all separatist stage of the primaryspermatocytes clearly, occasionally sperm. During this period spermatogenic epitheliumhas developed, but very little sperm formation. There weren't sperm fertilizationcapacity basically during this period, so it was not reached sexual maturity. It wasadolescence. 45 days after birth, a considerable number of sperm were produced inadluminal compartment. There were sertoli cells, spermatogonia, primaryspermatocytes, secondary spermatocytes, spermatids and sperm in spermatogenicepithelium, and primary spermatocytes, spermatids and sperm chiefly. Spermatogenicepithelium was more than 5 layers. Meanwhile, a large numble of sperm were producedin epididymis duct cavity, columnar epithelial cells arranged in order and mesenchymaldeveloped. These characteristics suggeste that root voles of this period has enteredsexual maturity. For 50 days, the duct cavity diameter increased and cavity surfacedistributed more sperm. Spermatogenic epithelium cells had various distribution.55～70days after birth group, a large number of sperm were distributed in adluminalcompartment, but more sperm with osteoporosis.Spermatogenic epithelium cells haddifferent distribution, sertoli cells scarcely, spermatocytes and spermatids principally.Spermatogenic epithelium had more layers. Adult group, there were a large number ofsperm in adluminal compartment and they were working closely with bundles.Spermatocytes and spermatids distributed more widely in Seminiferous epithelium.Spermatogenic epithelium was nearly 10 floors. These proved that Microtus oeconomushas entered the sexual maturity after the 45th day.3.We can see clearly the epididymis tube in epididymis of Root Voles at one day afterbirth.Cavity Surface ruled, nor details were available, for a layer of the wall of columnarepithelial cells, as a thick tube surrounded by the smooth muscle.Born 7 days old, thelayers of columnar epithelial cell increased. For 11 days old, the cavity relativelynarrowd, and columnar epithelial cells in the wall of the distribution messed.Born 14-day-old group, the lumen increased significantly, wall thinning, the cavity was acidicsubstances produced. Smooth muscle layers reduced and its distribution was sparse.Stereocilium produced on the free surface of cell. Born 21 days old, possession weekedmessy smooth muscle cells, further increasing the lumen. The cavity surface ruled, andthe cavity more acidic substances in. For 30 days old, pseudostratified ciliated columnarepithelium existed in epithelium, with a large number of stereocilium distribution in thefree surface, Week of muscle cells thinning, a cavity still had acidic substances. Born 35days, the lumen increased and cavity part dyed deeper, pseudostratified ciliatedcolumnar epithelium ruled, Week of muscle cells became thin, and fatty substanceproduced. For 40 days, possession of a small number of epididymis cavity might bedistributed sperm. Born 45 days, in epididymis cavity there were a large number ofsperm, columnar epithelial cells with a very neat, and mesenchyme developed.This alsodemonstrated that the root voles at this stage was to enter sexual maturity.Born50-day-old group, massive sperm found in the center of epididymis lumen, closing wallbecame thin, epithelial cells and muscle closely linked. From 55 to 70 days group, thenumber of sperm was further increasing and the wall of epididymis was changingthinner.Week of muscle cell layers were reduced and the wall of epididymis wasconnected with it. Adult group, a rare muscle cells possess, mesenchyme was scarce,and a large number of sperm was in.All these showed the synchronicity of developmentbetween epididymis and testis.4. There are three obvious growth stages in the development of testis mass and volumein Microtus oeconomus:1～11d, 14～35d, 40～50d. Along with the increasing of age,development of testis index gradually increased and then moved to stability.It can beconcluded that there were more changes during these periods in Microtus oeconomus.5. Microtus oeconomus with Microtus mandarinus, mice were compared, thedevelopment of mesenchymal cells are prior to epididymis in this three species.Thisindicates the development of epididymis was affected with androgen secreted byinterstitial cells, and the identity of the development of the male gonad in threemice.There were few specific morphological differences in the testis and epididymis of thedevelopment cycle in three mice. And there were only obvious differences in the testisand epididymis.The seminiferous tubule diameter of three mice is: mice＞root vole＞Microtus mandarinus, and the difference among them is more apparent. Overall, therewere obvious growth changes about the male gonad with the growth of three mice.At the beginning, the three mice all experienced incomplete development of germinalepithelium, and the stage in which there were only sertoli cells, spermatogoniumspermatogenic cells.Then a small amount of primary spermatocytes produced.Thefollowing various spermatogenic cells could be found in the epithelium.Subsequently,sperm produced. Along with the growth of age, a large number of sperm existed, andthree mice all entered their sexual maturity.Meanwhile, the development of testis andepididymis was basically synchro in three mouse. However, the stage of sexual maturityand concrete characteristic were different in three mice because of the diffenence oftheir growth environment. In Microtus mandarinus, mature sperm appeared at 45days, a large number of sperm matured in eminiferous tubule and epididymis at 60days.Microtus mandarinus entered adolescence at about 45 days, reached sexualmaturity at about 60 days.ICR mice entered sexual maturity from 30 days.In Microtusoeconomus, sperm could be seen in the 35-day-old, but those of 40 days is not veryclear, 45 days were large. And there are also a large number of sperm found inepididymis at 45 days.Therefore, Microtus oeconomus should enter adolescence at 35days or so, and reach sexual maturity about 45 days.In summary, the development cycle of Microtus oeconomus should be divided intofour periods as following: 0～14d—early development, 14～35d—adolescence, 35～50d—sexual maturity, 50 days after entering into the adult phase.