Any of numerous aquatic or terrestrial mollusks of the class Gastropoda, typically having a spirally coiled shell, broad retractile foot, and distinct head.
蜗牛：腹足科众多水生或陆栖软体动物中的一种，通常带有一螺旋似的厚壳，足宽且向内旋，脑袋清晰。
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Few species, low biomass and lack of blue green algae, Gastropoda, Lamellibranchia and Crustacea are most notable characteristics distinguished from general neutral and alkaline lakes.