Fish are aquatic vertebrate animals that are typically ectothermic ( previously cold-blooded ) , covered with scales , and equipped with two sets of paired fins and several unpaired fins .
魚是水生脊椎動物,典型特征是屬冷血動物,全身有鱗片,有一對魚鰭或幾個不成對的魚翅。
Mobile ectothermic animals can control their body temperatures by selecting specific thermal conditions in the environment , but embryos-trapped within an immobile egg and lacking locomotor structures-have been assumed to lack that ability .