Study On Monocrotophos' Toxicity To The Embryo Development Of Hemicentrotus Pulcherrimus

Recently, more and more papers report on the hermaphrodite of marine animals, abnormity of reproduction organ, embryo development and sex behaviors, and the decrease of reproduction quantity. But few papers report on the organphosphorus pesticides'effect on the early embryo development of marine creature. In this paper, a kind of common marine animal in the offing of Qingdao, Hemicentrotus pulcherrimus is used for investigating the effects of monocrotophos. The toxic effects of monocrophos on the sea urchin are studied on morphological, developmental and histological levels as an attempt to offer some fundamental data to establish a fast, efficient and practical biological technology for monitoring and testing in vitro. The results are as follow:1. It demonstrated that the early embryo development from fertilized egg to 2-arm plutei took 36h in our lab. The periods of Hemicentrotus pulcherrimus embryo's early development are as follow (pf: post fertilization): pf15min-pf1h30min: 2-cell stage; pf1h30min-pf2h15min: 4-cell stage; pf2h15min-pf3h: 8-cell stage; pf3h-pf10h: multi-cell stage; pf10h-pf12h: blastula stage; pf12h-pf18h: gastrula stage; pf18h-pf30h: prism stage; pf30-pf36h: 2-arm stage.2. Monocrotophos with the concentrations of 0.01, 0.10, 1.00, and 10.00 mg·L^-1 can seriously decrease the sperm's fertilization rate and quality, but have no obvious effect on the egg's fertilization rate. Sperms and eggs were exposed to monocrotophos separately, and then fertilized them with normal eggs and sperms artificially. It was found that a delay occurred on the later stage of embryo development even under the lowest concentration of 0.01 mg·L^-1 monocrotophos. The delay occurred from the blastrula stage, and prolonged with the increasing concentration of monocrotophos. Simultaneously many larvae became abnormal and even dead, and the rate of abnormality and mortality became higher with the increasing concentration of monocrotophos. Therefore, the toxicity effects of monocrotophos on embryo development are dosage-related.3. We exposed embryos to monocrophos separately during pf15min-pf12h, pf12h-pf18h and pf18-pf36h. We figured out the sensitive stage of embryos to the toxicity of monocrotophos is pf12h-pf18h, with the phenomenon of the most abnormal individuals and the longest embryo development. Monocrotophos with the concentration of 1.00 mg·L^-1 can obviously postpone the elongation of archenteron, and embryos can not develop normally even after removing monocrotophos. When it came into the 2-arm stage, the growth of arm was also effected, and the effect is dosage-related too. Therefore, pf12h-pf18h is the most sensitive stage for embryos to monocrophos'toxicity.4. The ultrastructure and development of Hemicentrotus pulcherrimus testis was observed by using electronic microscope. The results demonstrated that 1.00 mg·L^-1 monocrotophos caused the damage of testis, such as the dissolution of acrosome and nuclear membrane, slight dropsy and rupture of sperm membrane, dissolution of extima and cirstae of mitochondria. The ultrastructure changes of the three cells were related to concentration. Furthermore, 10.00mg·L^-1 monocrophos caused the reduction of mature sperm, aggregation of immature sperm at different developmental stage; dissolution of nuclear and cell membrane, serious dropsy of sperm membrane and the abnormality of the cell metabolism. Besides, many vacuoles occurred in yolk, finally leading to the dissolution of yolk.In conclusion, monocrotophos has toxic effect on both Hemicentrotus pulcherrimus gametes and embryos. The rate and quality of fertilization decrease significantly when sperm exposed to monocrotophos before fertilization. The embryo development was postponed from the blastrula stage as the elongation of archenteron was postponed and the growth of larvae's arm was interrupted. All the above phenomena caused by monocrotophos are concentration related. With the characteristics of gametes and embryo model's sensitivity to monocrotophos'toxicity, short early embryo development and transparence of embryo and larvae, Hemicentrotus pulcherrimus gametes and embryos are first proposed to be used as models to study organphosphorus pesticide's embryo toxicity.