A study of the skull and the musculature of the oral and pharyngeal region of four adult Carapidae species (Encheliophis boraboreruis, E. homei. E. gracilis and Carapus acus) has been undertaken to compare it with the diet related characters. The cephalic organization of E. boraborensis and E. gracilis seems related to diet (mainly fishes and shrimps for the first one and holothurian tissues for the other): these species are respectively commensal and parasitic. Although the feeding characters of E. homei and C. acus are closely similar to those of E. boraborensis, there are sparse observations of holothurian tissues in their stomach contents. It is suggested that these fishes are commensal when they are adults and have parasitic tendency when they are juveniles
