The darkened and distensible throat pouch of the adult male probably is the best available indicator of sexual maturity.
Its powerful voice is due to the distensible resonator which it possesses in its laryngeal pouch, described above.
Certain genera possess also sacs formed by distensible folds of the skin in the cheeks.
Inflate the œsophagus with a blowpipe and note how distensible is its lower end near the breast.
In some the bones are joined by distensible ligaments and the fish can swallow other fishes larger than itself.
Upon this flexible anterior part there are four short but distensible tentacles.
Hyla bistincta differs from other members of the group in having vocal slits and a distensible vocal sac.