2,4-DCP对若蚓期、成蚓期赤子爱胜蚓毒性效应研究

Toxic Effect of 2,4-DCP on Eisenia fetida at Growth Stage and Adult Stage

广泛使用的2,4-二氯酚(2,4-DCP)是一种常见的难降解有机物,在土壤中有一定的残留。为研究其急性毒性效应,分别以生长阶段为若蚓期、成蚓期的赤子爱胜蚓(Eisenia fetida)为受试生物,采用滤纸接触法和两室趋避试验探讨不同暴露剂量2,4-DCP对蚯蚓的急性毒性响应。结果表明,滤纸法测得若蚓期蚯蚓24 h、48 h和72 h-LC 50分别为80.71、76.20、73.64μg·cm^(-2),而成蚓期蚯蚓的分别为82.88、77.63、74.65μg·cm^(-2),略高于若蚓期;蚯蚓的中毒现象表现为部分环节肿大并渗血、躯体颜色变透明、躯体萎缩与断节等。两室趋避试验表明,当土壤中2,4-DCP浓度为10 mg·kg^(-1)时,清洁土壤中蚯蚓占比高于总数的80%,即表现出明显的趋避行为。蚯蚓组织切片显微观察结果表明,70.74μg·cm^(-2)浓度暴露下蚯蚓表皮结构受损,黄色细胞破裂,而88.42μg·cm^(-2)浓度暴露下蚯蚓表皮严重溃烂坏死,纵肌细胞间隙扩大,黄色细胞和肠上皮细胞发生破裂、变性并与肠壁分离;滤纸法暴露24 h时,蚯蚓体内蛋白质含量、SOD活性和CAT活性随2,4-DCP暴露剂量呈现先上升后降低趋势,表现出较明显的低剂量刺激和高剂量抑制效应;低浓度2,4-DCP胁迫下,若蚓体内的蛋白质含量、SOD活性和CAT活性显著高于成蚓;长时间高浓度暴露下的若蚓体内SOD活性、CAT活性几乎均低于成蚓。蚯蚓在若蚓期、成蚓期这2个生长阶段对2,4-DCP表现出不同的应激效应,其耐受能力也存在差异。

The widely used 2,4-dichlorophenol(2,4-DCP)is a common refractory organic material and has some residuals in the soil.To investigate its acute toxic effect,Eisenia fetida,which was at the growth and adult stages of development,was taken as the test organism,and the acute toxic response of earthworms to 2,4-DCP at different doses of exposure was investigated by means of the filter paper contact method and the two-compartment avoidance test.The results showed that the LC 50 measured by filter paper method was 80.71,76.20,73.64μg·cm^(-2) respectively at 24,48 and 72 h at growth stage,and 82.88,77.63,74.65μg·cm^(-2) respectively at adult stage,which was slightly higher than that at growth stage.In the earthworm poisoning phenomenon,some of the links are swollen and bleeding,the color of the body becoming transparent,the body shrink,and the broken segments.In the two-compartment avoidance test,when the concentration of 2,4-DCP in the soil was 10 mg·kg^(-1),the earthworm comprised more than 80%of the total number in the clean soil that exhibited signifcant avoidance behavior.In 70.74μg·cm^(-2) concentration group,earthworm epidermis structure damaged,chloragogenous tissue ruptured,while in 88.42μg·cm^(-2) concentration group,earthworm epidermis was severely ulcerated and necrotic,the cellular lacunae widened in the longitudinal muscles,and the chloragogenous tissue and intestinal epithelial cells ruptured,degenerated,and separated from the intestinal walls.In earthworms,protein content,SOD activity,and CAT activity initially increased and then decreased with 2,4-DCP exposure dose during 24 h exposure by the filter paper method,showing a significant low-dose stimulation and high-dose inhibition effect.The protein content,SOD activity,and CAT activity of growing earthworms under low-concentration 2,4-DCP stress were significantly greater than those of adults.Under long-term exposure to high concentrations,the activity of SOD and CAT in the growing-stage earthworm body is almost less than that of adult earthworms.Earthworms have been shown to have different response to stress of 2,4-DCP in the growth and adult stages,and their tolerance is also different.