Meeting Abstract
Lanternfishes are a diverse family of fishes with 246 described species that live in open ocean waters worldwide. These fishes are estimated to account for over 60% of deep-sea fish biomass and are crucial food sources for many larger fishes, cetaceans, and squids. Many lanterfishes live deeper in the water column during the day, but migrate closer to the surface at night to consume zooplankton. Despite the clear ecological and evolutionary importance of lanternfishes for open ocean environments, we generally know little about this group due to the difficulties of observing them alive. In order to develop our ecomorphological knowledge of lanternfishes, we have used µCT to study their cranial morphology, with a special focus on pharyngeal jaws. Pharyngeal jaws are common to all teleosts and are a second set of jaws formed by modifying the posterior-most set of gill arches into tooth-bearing bones that can help process and transport food. We demonstrate that one clade of lanternfishes (Gonichthys spp. and Centrobranchus spp.) have highly modified pharyngeal jaws, where the upper tooth plates have enlarged molariform teeth and appear to occlude in a lateral-medial fashion, as opposed to the normal arrangement where upper and lower tooth plates occlude in a dorso-ventral fashion. The modified upper pharyngeals are hypertrophied and crush prey between the left and right upper tooth plates using enlarged musculature and a novel muscle attachment. Unlike other lanternfishes, the clade of species with modified jaws specializes in consuming planktonic shelled gastropods. This discovery represents a unique and novel instance of durophagy by a small-bodied, open-ocean, and zooplanktivorous group of fishes.
