Ma'anar ƙamus na kalmar "costal groove" tana nufin tsagi ko furrow wanda ke gudana tare da saman ciki na haƙarƙarin wasu dabbobi, musamman kifi da masu amphibians. Ƙarƙashin farashi yana ba da tashar karewa don tasoshin jini na intercostal da jijiyoyi waɗanda ke gudana tare da ƙananan haƙarƙari, suna taimakawa wajen hana lalacewa ga waɗannan sifofin yayin motsi. A cikin kifaye, ana danganta tsagi mai tsada da tsarin layi na gefe, wanda ke taimaka wa kifin don gano rawar jiki da canje-canje a cikin ruwa.