海绵(sponge)
多孔动物门约5,000种固着生活，多数为海生，独栖或群居的无脊椎动物的统称，分布自浅水至深水（超过9,000公尺）水域。简单的海绵呈中空圆柱状，顶端有一大型开口，水和废物经此开口排出。薄而穿孔的外表皮层覆盖着多孔的骨骼，是由互相连结的碳酸钙、矽或海绵硬蛋白（存在於80%的海绵种类中，为似蛋白质的物质）所组成。海绵的体型直径大小可自2.5公分至数公尺长，可能为手指般大小、树般大小或为没有形状的一团物体。海绵缺乏器官和特化的组织，具鞭毛的细胞将水自孔送入中央空腔，个别的细胞消化食物（细菌、其他微生物和有机物残骸）、排泄废物和吸收氧气。海绵可行无性和有性生殖。幼体可自由游泳，但所有成体皆固着生活。海绵自古代就被采收使用在吸水、沐浴和洗刷上。由於过度采收和更新的科技，今日所贩卖的多为人工合成海绵。
English version：
sponge
Any of some 5,000 species (phylum Porifera) of permanently affixed (sessile), mostly marine, solitary or colonial invertebrates, found from shallow to deep (more than 30,000 ft, or 9,000 m) waters. Simple sponges are hollow cylinders with a large opening at the top through which water and wastes are expelled. A thin, perforated outer epidermal layer covers a porous skeleton, which is composed of interlocking spicules of calcium carbonate, silica, or spongin (found in 80% of all sponges), a proteinaceous material. The body, ranging in diameter or length from 1 in. (2.5 cm) to several yards, may be fingerlike, treelike, or a shapeless mass. Sponges lack organs and specialized tissue; flagellated cells move water into the central cavity through the perforations, and individual cells digest food (bacteria, other microorganisms, and organic debris), excrete waste, and absorb oxygen. Sponges can reproduce asexually or sexually. Larval forms are free-swimming but all adults are sessile. Since antiquity, sponges have been harvested for use in holding water, bathing, and scrubbing; because of overharvesting and newer technologies, most sponges sold today are synthetic.
