Both sea stars and sea cucumbers are belong to the phylum Echinodermata (the Latin name means "spiny-skinned"). Their body consists of five equal segments, each containing a duplicate set of various internal organs.
海星和海参都属于棘皮动物。据说它们幼体时两侧对称，长大后辐射对称。
Juvenile knobbly sea stars，one with six arms 多节海星大部分有五个胳膊，受损后可以再生。不过生物界总有例外，右边的居然有六个胳膊。
Adult knobbly sea star
Sand sifting sea star
It can dig into the sand quickly 这种海星可以很快把自己埋到沙子里
Sand sifting sea star move and dig by these numerous tube feet 海星依靠腹面众多的管足行动的
Sandfish sea cucumber
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