Morphological Study And Toxic Effects Of Pb²⁺ On Polychaete Perinereis Aibuhitensis

The present study analyzes the relationship of morphological parameters and thetoxic effects of Pb2+on polychaete Perinereis aibuhitensis. The part of morphologicalmainly study the normal state and epitoky, which also known as heteronereis, in P.aibuhitensis, morphological parameters, such as body length, head length, body width,weight and somites number are measured. SPSS16.0was applied to model the fittinganalysis for the relationship of different parameters. The part of toxic effects to assessadverse biological effects caused by Pb2+in artificial seawater under controlledlaboratory conditions. The results are as follows:Morphological study on the normal body and epitoky of P. aibuhitensis indicatedthat:1) the weight of P. aibuhitensis in its normal state presents a cubic functionalrelationship along with body width and body length;2) the weight of heteronereispresents a cubic functional relationship along with somites number and body length inits reproductive area, and presents a cubic functional relationship along with the bodylength and body width in its non-reproductive area;3) the length of heteronereis isshortened, which approximately half of the length in its normal state with the samenumber of somites number, and the reproductive area appears to be composed ofsexual somites;4) the length-width ratio in normal state is about23, while the ratio inheteronereis is only about8. According to this study, the standard of adult worm is140mm in length,6mm in width; while the standard of heteronereis is80mm in length,10mm in width. What’s more, the body of heteronereis apparently divided into creepzone and swimming zone, and it can swim freely, meanwhile, their eyes get biggerand the color of dorsal body is changed from red to brown. These morphologicalparameters and the changes of the body can provide relevant evidences for theartificial breeding and reproduction of P. aibuhitensis.Acute and chronic toxic effects of Pb2+on polychaete P. aibuhitensis:morphological changes and responses of the antioxidant system indicated that:1) in 96h acute toxicity experiments (125mg/L,250mg/L,500mg/L,750mg/L,1000mg/L and1250mg/L), the morphological changes showed a positivetime/dose-dependent phenomenon. Color changed from brownish to gray on day1.Proboscis looked valgus and swollen on day2. Sequently, unnatural breaking in theposterior region and exposed guts can be found on day3and4. Rupture in epidermisand cuticle, bleeding and green fluorescence in appearance as well as swollen anteriorparts were observed both on day1in higher concentration of Pb2+treatment (750mg/L,1000mg/L,1250mg/L) and on day2in lower concentration of Pb2+treatment(250mg/L). LC50value of Pb2+, which was calculated based on the mortality data ofadult P. aibuhitensis, was686.41mg/L.2) the responses of enzymatic andnon-enzymatic antioxidants in tissues, including catalase (CAT), peroxidase (POD),superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), malondialdehyde(MDA) and the content of total soluble protein (TSP), were investigated on day1,4,7and10after Pb2+exposure under chronic toxicity tests (0mg/L,3.13mg/L,12.50mg/L,25.00mg/L and50.00mg/L). Results showed that: when exposed to higherPb2+concentrations (25mg/L and50mg/L), the activity of CAT kept in the roughlysame level on day1,7and10, which were significantly higher than that on day4.Compared with the control, POD activity under the stress of Pb2+was induced on day1and little difference was observed on day7. On day1, the activity of SOD washighly increased with the comparison of the control, and the treatment groupsremained in a similar state on day7and10. Various concentrations of Pb2+and theduration of exposure time reveal a phenomenon that toxic effects could stimulateGSH-PX activity and the content of MDA. The content of TSP showed a risingtendency over exposure time when the worms were exposed to25.00mg/L Pb2+. Ourresults suggested that the activation of antioxidants in P. aibuhitensis depended on theconcentration of Pb2+and the duration of exposure time. The conclusions as follows:POD and SOD were induced at the first day of the exposure, then significantlydecreased and recovered to the control level, until10days, these two indicatorspresents a disorder state. The vitiation of these two indicators can indicated P.aibuhitensis can activate its antioxidants to defense toxicity effect firstly when under the adverse environment, subsequently, recovered to the control level to adapt theadverse conditions gradually, and with the exposure time extended, the worm couldnot deal with adverse factors, reflected in the activities of these two antioxidantsdisordered. Thus, we think POD and SOD can be used to indicate oxidative stress ofPb2+in P. aibuhitensis.