检索表 1a 有脊椎骨·····················································2 1b没有脊椎骨、鳞、鳍等结构 ····················3 2a身体银白色·················································甲 2b身体金黄色·················································乙 3a身体没有外骨骼··········································丙 3b身体有外骨骼,足分节······························丁 |