土壤镉污染对赤子爱胜蚓(Eisenia fetida)和加州腔蚓(Metaphire californica)体表角质层的影响

The Impact of Soil Cadmium on the Ultrastructural Cuticle of Two Earthworms Species Eisenia fetida and Metaphire californica

利用镉(Cd)污染土壤(0.15、7.28、13.53、16.45 mg?kg^(-1))在室内培养赤子爱胜蚓(Eisenia fetida)和采集野外原位污染(0.84、2.17、5.16、6.38、9.83 mg?kg^(-1))土壤中的加州腔蚓(Metaphire californica),使用JEM^(-1)230型透射电镜观察不同质量分数Cd污染土壤对赤子爱胜蚓与加州腔蚓体表角质层超显微结构的影响,分析其与土壤中Cd的关系,探寻其在Cd污染条件下的变化规律,并对蚯蚓体壁在防御重金属毒性中的作用进行初步研究,旨在揭示Cd长期污染条件下蚯蚓的生态适应性,为正确地开展土壤污染生态风险评价提供科学依据。研究结果表明,在Cd低污染条件下赤子爱胜蚓(Cd<7.28mg?kg^(-1))和加州腔蚓(Cd<5.16 mg?kg^(-1))上角质层突起(微绒毛)排列较为整齐有序,在Cd高污染条件下其上角质层突起变得稀疏无序,并且污染严重时会出现颗粒化或缺失现象。赤子爱胜蚓和加州腔蚓的角质层均随着土壤Cd质量分数及蚯蚓体内Cd的质量分数的升高呈现出先增厚后变薄的变化规律,且在各处理条件下都能正常生存。由此可知,在Cd污染土壤中,不同种的蚯蚓可以通过调节角质层厚度来适应受污染的土壤环境。

n this study Eisenia fetida was cultivated and exposed to cadmium （Cd） contaminated soils with mass fraction of 0.15, 7.28, 13.53, 16.45 mg？kg-1 and Metaphire californica was sampled from historic cadmium （Cd） contaminated areas with mass fraction of 0.84, 2.17, 5.16, 6.38, 9.83 mg？kg-1 in Huanan Province. The toxic effect of cadmium （Cd） on the ultrastructural cuticle of two earthworms species was studied with transmission electron microscope （TEM）. The relationship was analyzed between the variety of earthworm’s ultrastructural cuticle and the mass fraction of Cd in soil, in order to study the variation of the earthworm’s ultrastructural cuticle in Cd-contaminated soil, and the influence of heavy metal on earthworm cuticle. The aim of this study was to reveal the ecological adaptability of earthworms in long-term pollution soils and of Cd, and to provide the scientific basis for evaluating ecological risk of polluted-soil correctly. The results showed that the up-cuticle protuberances （microvilli） in earthworms appeared orderly under low soil Cd pollution（Cd〈7.28 mg？kg-1） for Eisenia fetida and Cd〈5.16 mg？kg-1 for Metaphire californica. They became sparse and disordered and even disappeared, with the increase of Cd pollution in soil. Meanwhile, the cuticle thickness increased with soil Cd pollution both in Eisenia fetida and Metaphire californica. However, it indicated decreased tendency with relative high soil Cd pollution, and there were no deaths in the Cd contaminated soils. The change of ultrastructural cuticle would be one mechanism of earthworms to adapt to Cd contaminated soil.