Cephalic specializations in relation to a second set of jaws in muraenids

Abstract

The Muraenidae, one of the largest clades within the anguilliform fishes, exhibit an innovative feeding mechanism that allows them to transport large prey items from the oral jaw all the way back towards the esophagus, using highly specialised pharyngeal jaws. This study was conducted to show the degree to what trade-offs in muraenids may have arisen in the oral feeding apparatus, in relation to this pharyngeal transport system. Hence, the head musculoskeletal features of Anarchias allardicei (Uropterygiinae: Muraenidae) and Gymnothorax prasinus (Muraeninae: Muraenidae) were compared with that of a closely-related out-group with a hydraulic based prey transport, Ariosoma gilberti (Bathymyrinae: Congridae) by providing a detailed description of the cranial osteology and myology of A. allardicei and G. prasinus. The result showed that this innovative feeding mechanism may be linked to many cephalic modifications such as, stout and robust neurocranial elements, elongated lower jaw as result of the posterior position of the quadrato-mandibular articulation, enlarged teeth of oral jaws and premaxillo-ethmovomeral complex, reduction in the moveable cranial bones and their muscular connections, hypertrophied adductor mandibulae muscle complex, presence of the quadrato-maxillary and preoperculo-angular ligaments, connection of the quadrate to the A2 tendon of the adductor mandibulae complex and caudoventral orientation of the fibers of the large A3 section of the adductor mandibulae complex.