Toxic Effect And Mechanismon Study Of 4-Nonylphenol On Poecilia Reticulata

4-nonylphenol is a kind of multipurpose non-ionic surface active agent, belonging to thealkylphenol compound. NP can enter into the soil, food and the tap water through biologicalaccumulation and thus does harm to the health of animals and human being. It has been welldocumented that NP is a kind of estrogen synonyms and can enter into animals and human bodiesby biological chains, and further more affect their reproductive system, inernal secretion,immunity and cardiovascular functions. The growth of fish is under the regulation of endocrinesystem and the hormone plays a vital role in sex differentiation and germ cells growth. Therefore,extraneous estrogen synonym will disturb the normal development of fish.Poec ilia ret icul ata is a ovoviviparity fish with different sexes that are easy tosutdifferentiate by appearance, and its breeding cycle is short. Further more, guppy is sensitive tokinds of pollutants and thus can be suitable for toxicology research. Little information is availableon the effects of long-term, chronic exposure of guppy to nonyl phenol on its reproductive system.The toxic effect of NP on the guppy was determined utilizing a whole-generation (90 days)exposure in the present study, based on which the dose-effect relationship was worked out.(1) Nonyl phenol, showed an effect of endocrine disturbance. More female were induced inthe treatment of NP which could be evidenced by the longer copulation organ compared with thecontrol and solvent control. The results of growth index and liver index indicated that NP had ansignificant negative influence on the growth of the guppy exposed in low concentrations. Theeffect of NP on male was stronger than that of female. The sexual gland index derived from 25,125 and 250 ug/L were less than that in the control. The liver indexes calculated from 125 and 250ug/L treatment were significantly higher than that from the control which could be associated tothe synthesis of VTG in the liver.（2）Nonyl phenol had an influence on guppy’s reproductive ability. Male guppies showeddimmed body color, slowed hovering speed and reduced frequency of S- and C-type dances when 1 day old guppies were exposed to NP for 90d and continued for another 60 days. The treatmentsof NP had significant effects on breeding females, spawning times, the number of offspring andthe survival of offspring. The results abovementioned indicated that NP could disturb the normalreproduction of guppy and do harm to the fitness of its offspring.（3）The results from histopathology observations indicated serious damages in guppy testis.The micrograghs shows that the spermatocyte and Senoli cells in the testes have been seriouslydamaged as a result of exposure to monocrotophos and exhibited a time-dependentefect．Furthermore，the chromatin of sperm atocyte has been noticeably extravasated．We havealso found that a number of cysts with partly lysed basement membrane appear with the prolongof the exposure time length，some of which were even fused with other cysts．Moreover，thespermato genetic stage proves not the same in one cyst．In testes，the cysts containing all thediferent sperm atogenetic stages are fourld to have decreased in number with the irregularlyarrangement．Compared with the control group，the testes of the exposed fish now contain lesssperm atogenetic cysts but wi th more mature spermatozeugmata and free spermatozoa．Thus，theresults indicate a tendency of transform ation from the originally existing spermatogenetic stageinto spermatozeugmata，with no replenishment of the early stages．Mean while，some cavities havebeen detected in the centre of testes at the end of exposure．Most of the efferent duct membraneslysed and the hypertrophied Sertoli cells increased，leading to the partly disintegration of some ofsperm atozeugmata and more free sperm atozoa in the testes．Thus．the above results help todisclose that the monocrotophos have impaired the sperm atogenesis and decreased the numberand density of sperm of male guppy，and eventually resulting in the unhappy reduction of theiroffspring．...