| The red-eared turtle(Trachemys scripta elegans) is one of the top 100 invasive specie s worldwide. It has been confirmed that Trachemys scripta elegans can successfully re produce in Taiwan, Hainan, Guangdong, in China, and elsewhere. Its fecundity and sur vival greatly exceed those of our native turtles. Trachemys scripta elegans is favored b y many turtle farmers because it is lively, colorful, very easy to feed and easy to sell. In 2009, farms in China produced more than fifty million turtles. Annual imports from abroad are around eight million turtles. Of the total of nearly 60 million turtles, most are sold in the domestic market but some are exported, primarily to Southeast Asia.Due to such large scale farming, the inevitability of widespread escapes during transp ortation and in the management oversight process, and the more serious practice of rel easing Trachemys scripta elegans by well-intentioned people will lead to the increasin g establishment of feral populations. The discarding of former pets, or release based on religious principles further complicates law enforcement efforts due to confusion ofTrachemys scripta elegans with protected native species. Feral populations will be harmful to the natural ecosystems of our country. There is little indication that a cha nge in policy will put a stop to this dangerous trend.At present, research on the methods of effective control of Trachemys scripta elegans is almost non-existent here and overseas. Preventative measures must be undertaken urgently. Based on the huge success of sterilization control techniques on insect and rodent pests, we propose that sterile control technology be used to control the alien species Trachemys scripta elegans. Considered from the points of view of ecology and biology, sterile control technology is a fundamental measure of choice. Through reference to and filtering a large amount of information on chemosterilant, and based on preliminary experiments, we have studied the efficacy of tris(2-methyl-1-aziridinyl)pho-sphine oxide(MAPO) on the reproductive function of male Trachemys scripta elegans by detecting the viscera coefficient, testicular volume, paraffin tissue section and Motic Images Advanced 3.2 software. Our preliminary exploration of its action mechanism has been by use of ELISA to detect hormonal changes, antioxidant enzymes and marker enzymes. We have researched the reversibility of chemosterilization by the late detecting viscera coefficient of Trachemys scripta elegans’ s testis and epididymis, paraffin tissue section and hormone assay. These will provide the scientific basis for preventing the establishment of the alien species Trachemys scripta elegans.The main research results are as follows: 1. The sterility effect of male Trachemys scripta elegans caused by MAPOWe selected healthy, adult male Trachemys scripta elegans(BW: 738.9 + 101.2g, n=160) which were randomly divided into 4 groups: control group, and low, medium, and high dose group, each group consisting of 40 individuals. We used intraperitoneal injection of 2 ml MAPO at a concentration of 0.1 g/L, 3 g/L, 10 g/L of saline solution, for the low, middle, and high dose group, respectively. These were administered to each turtle five times in the 15-day course. The control group turtles were injected with the same quantity of 0.65% saline solution at the same schedule. These respective treatments were carried out for 15 d. The results show that the Trachemys scripta elegans of the low and middle dose groups remained agile, healthy, and lively, their food intake and body weight basically the same as the control group’s. Their survival rate was 100%. But the food intake of the high dose group declined and the survival rate was 0%. Results indicate that the five serial injections at a dosage of 8mg/Kg or less did not affect the health of the male red-eared turtles.Compared with the control group, no significant differences were found in each treatment group’s viscera coefficient of kidney, liver, heart and epididymal function. No significant differences were found in the low dose group’s viscera coefficient(0.17 ± 0.07) and volume(4.63 ± 0.52) m L of testis compared with the control group. The viscera coefficient of testis(0.06 ± 0.02、0.08 ± 0.03) in the middle and high dose groups was significantly lower than the control group’s(0.15 ± 0.07). Testicular volume(1.83 ± 0.18、2.01 ± 0.54) in middle and high dose groups was also significantly lower than the control group’s(4.22 ± 0.73), about 50% as much. After histopathology observation, epididymis and kidney of each treatment group had no lesions, although the liver in the high dose group showed slight vacuolization. The structure of the seminiferous epithelium in the control group was orderly, from outside to inside, spermatogonias, primary spermatocytes and secondary spermatocytes in turn were present. The spermatogenic epithelium in the low dose groupwere arrayed loosely, secondary spermatocytes and spermatids were shed into the lumen. Theseminiferous epithelium thickness of the low dose group(71.60 ± 21.61 μm) showed no significant difference compared with the control group. But spermatogenic epithelium was markedly thinned in the middle and high dose group, nearly completely degraded. The thickness of the seminiferous epithelium in the middle and high dose group was 9.67±8.67μm and 4.30±2.29μm, about one-tenth and twentieth compared with the control group, the difference between the middle and high dose group and control group was very significant, only sertoli cells close to the basement membrane and leydig cells were well developed in themiddle and high dose group. This indicates that MAPO has reproductive toxicity to the maleTrachemys scripta elegans, and the testis is the effector of MAPO. It can penetrate the blood-testis barrier, damaging germ cell levels, hindering sperm production, thereby causing infertility. 2. The primary research of the sterility mechanism of MAPO on male Trachemys scriptaelegansCompared with the control group, gonadotropins(FSH, LH, PRL) and sex hormones(T, E) content in the testis of each treatment group showed no significant difference, indicating that MAPO has no obvious influence on the hypothalamus- pituitary- gonadal axis adjustment system of Trachemys scripta elegans. Testicular marker enzymes in addition to the ACP(5.37±0.15 U/L) in the lower dose groups was significantly different from that of the control group(4.96 ± 0.12 U/L), other testicular marker enzyme had no significant difference. The antioxidant enzymes SOD(106.90 ± 4.89 U/L) and GSH-Px(32.85 ± 4.01 U/L) were also not significanlty different in comparison with the control group(102.08 ± 3.57 U/L, 33.32 ± 4.27 U/L). The middle and high dose groups’ testis marker enzyme LDH(4.71 ± 0.10 U/L, 4.64 ± 0.12 U/L), ALP(142.87 ± 1.99, 140.55 ± 3.66 U/L) was significantly lower than the control group, LDHx(4.19 ± 0.13, 4.16 ± 0.06 U/L) was very significantly lower than the control group(4.98 ± 0.11 U/L), antioxidant enzymes SOD(88.65 ± 3.02 U/L, 90.15 ± 3.04 U/L) was significantly lower than the control group(102.08 ± 3.57 U/L), as was GSH-Px(21.89 ± 2.39 U/L,20.66 ± 2.09 U/L)(33.32 ± 4.27 U/L). These findings indicate that MAPO can destroy testicular structure, causing germ cell antioxidant system disorders, which reduces activity of the testicles’ signature enzymes. 3. The Infertility reversibility of male Trachemys scripta elegans caused by MAPOFollowing recovery for 30 d, compared with the control group, no significant differences were found in low dose group’s viscera coefficient(0.18 ± 0.02) and volume(1.14 ± 0.13) m L of testis. The testis viscera coefficient of the middle dose group(0.07 ± 0.02) was significantly lower than the control group(0.17 ± 0.04), and testicular volume(0.58±0.05) m L was significantly lower than the control group(1.52 ± 0.51 m L). There are various levels of germ cells in the seminiferous tubules of the control group and low dose group, arranged in order from the basement to the cavity spermatogonia, primary spermatocytes, secondary spermatocytes, sperm cells, sperm, and a larger number of sperm in the lumen. The seminiferous tubules are cavitated in the middle dose group, sertoli cells confined to the vicinity the basement membrane.After recovery for 122 d, compared with the control group, no significant differences were found in the low dose group’s viscera coefficient(0.14 ± 0.02) and volume(1.51 ± 0.20) m L of testis, and the epididymis viscera coefficient(0.06 ± 0.01 mm) of the low dose group showed no significant difference from the control group.The testis viscera coefficient in the middle dose group(0.08 ± 0.01) was significantly lower than the control group(0.17 ± 0.02), the testicular volume(0.66 ± 0.07 m L) was significantly lower than the control group(2.34 ± 0.73 m L), as was the epididymis viscera coefficient(0.03 ± 0.00)(0.07 ± 0.01). After histopathological observation, the structural integrity of the seminiferous tubules is unabridged in the control group and low dose group, resulting in a significant number of sperm. The seminiferous tubules continued to be cavitated in the middle dose group, there are only Sertoli cells close to the basement membrane, and no sperm. A large number of sperm were present in the epididymis in the control group. The epididymis is empty in the middle dose group, without sperm. This finding after 122 d indicates that the sterile individual did not recover.In conclusion, MAPO has obvious reproductive toxicity for male Trachemys scripta elegans. It can penetrate the blood- testis barrier, damaging germ cells at every level, hindering sperm production, and causing irreversible reproductive disorder to male Trachemys scripta elegans. Here we introduce this fertility prevention technology so as to limit the establishment of new populations of Trachemys scripta elegans, after having researched the reproductive toxicity of MAPO on a reptile. This lays a scientific foundation for further developing and utilizing this fertility prevention technology to control Trachemys scripta elegans and expand the application range of the fertility prevention technology to halt the spread of a detrimental organism. |
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