Meeting Abstract

P2.86  Wednesday, Jan. 5  The Great Mouth Migration: A Tale of Two Arizona Fish KA’APU-LYONS, C.A.*; GIBB, A.C.; Northern Arizona University; Northern Arizona University Cassie.Lyons@nau.edu

We examine feeding behavior in two native Arizona fishes: razorback sucker (Xyraunchen texanus) and roundtail chub (Gila robusta). As adults, the jaws of these two species are dissimilar, which suggests they exploit different food resources. However, as larvae, the jaws are morphologically similar, which suggests that they may demonstrate similar feeding behaviors during early life history stages. Our studies indicate that both X. texanus and G. robusta possess forward-facing, terminal mouths as larva and will readily feed in the water column. During larval and juvenile development, G. robusta’s jaws remain in a terminal orientation; however, the jaws of X. texanus migrate toward the ventral surface to achieve the sub-terminal adult phenotype. X. texanus spent more time on the tank bottom as mouth migration progressed, thus this shift in behavior facilitates the benthic feeding habit demonstrated by adults of this species. We quantified behavior using high-speed video and considered three stages of jaw migration: early larval stage (both species possess a terminal mouth), late larval stage (X. texanus mouth is mid-migration), and juvenile stage (X. texanus mouth is sub-terminal). Our preliminary analysis suggests that maximum gape angle increases through development in both species. The angle of the premaxilla relative to the mid-coronal plane at rest (time 0) appears to be similar in the two species and, somewhat surprisingly, does not change during development in either species. However, at more advanced developmental stages, the upper jaw of X. texanus undergoes a greater range of movement, relative to G. robusta. These data support the hypothesis that these two species are similar to one another during the early larval stages, but feeding kinematics diverge as they enter into older, more adult-like, developmental stages.