Meeting Abstract
Lanternfish (Myctophidae) are a common and diverse group of small to medium sized deep-sea fish. They are an integral part of the vertical migration of deep-sea fish towards the surface each night, which in turn is vital for connecting the deep-sea with surface waters. This migration is where they consume a lot of their food, which generally consists of dominant meso-zooplankton groups such as copepods and amphipods. Past work suggests there may be little diet specialization in this group, although this may change in different locations and seasons. We sought out to study the pharyngeal jaws of lanternfishes to help us understand the evolution and morphological diversity of this group. Pharyngeal jaws are a second set of jaws located in the pharynx that aid with food processing. We CT-scanned almost a 100 lanternfish species and used software to isolate the pharyngeal jaw apparatus. Then we placed landmarks for geometric morphometrics, and made linear measurements. We found one clade of myctophids with highly modified pharyngeal jaws, adapted for processing hard-shelled prey. In this clade, the upper jaws are hypertrophied with molariform teeth, and the lower jaws are greatly reduced. This morphology suggests that the left and right upper jaws can push together and crush prey between them – a novel mechanism of jaw action for fishes. Relatives of this clade also have modified jaws with a similar potential for occlusion between left and right upper jaws. We further explore the diversity and evolution of pharyngeal jaw morphology in this group by studying pharyngeal jaw morphology across the entire family using modern comparative tools. This study highlights where in the Myctophid family these adaptations evolved and provides insight into the evolution of myctophid morphology and ecology.
