Diodon nicthemerus is similar in appearance and size to the three-bar porcupinefish (Dicotylichthys punctulatus), with both species reaching around 40 cm (15.7 inches) in total length, although patterning and morphology can differentiate the two. It is nocturnal, occasionally forms small groups, and feeds on benthic zoneinvertebrates. It possesses slender yellow spines used for defence against predators and has the ability to inflate its body so its sharp spines protrude when alarmed.[3]