体表には鱗が変化した棘が、350~400本程あります。普段は棘を体に沿って寝かせていますが、

外敵に遭遇したり刺激を受けたりすると、体を膨らませて身を守ります。

The body surface of Harisenbon is covered many spines that are modified scales, but the actual number of spines is about 350 to 400. Normally, they lay their spines close to the bodies, but when they encounter enemies or are provoked, they inflate their bodies to protect themselves.