Meeting Abstract
Frogfishes (Antennariidae) are a family of anglerfishes (Lophiiformes) that are capable of jet propulsion, a type of locomotion that involves shooting a jet of water out the gill openings to propel forward. Using the gill ventilation system, these organisms can avoid stereotypical locomotor movements that may be visual cues to predators and prey. Jetting is primarily accomplished by adduction of the opercular bones and branchiostegals, which compresses the gill chamber. Frogfishes have abnormally large branchiostegals for both jetting and gill ventilation. Our study aims to map the evolution of the size of branchiostegals among frogfishes to determine which rays are shaped by demands of jet propulsion and to determine the timing of movements of structures during jet propulsion. We grouped six branchiostegal rays into three groups of two, numbered anteriorly to posteriorly, and predicted rays 1-2 are used for inhalation, 3-4 are used for jet propulsion, and 5-6 are used for exhalation. CT scans and dissections were used to measure the rays, and phylogenetic generalized least squares models were used for comparisons. We found that branchiostegals within the same group were the same size (relative to head size), but there was a significant size difference among branchiostegals in different groups. Therefore, we concluded that each group of branchiostegals is evolving independently from the others. Additionally, we used video analysis to show that jet propulsion is dominated by compression, providing a long jetting phase, facilitated by branchiostegals three and four.
