DOI: 10.5061/dryad.3j9kd51t1
title: Suction feeding turned on its head: a functional novelty facilitates lower jaw protrusion

description: Functional novelties play important roles in creating new ways for
 organisms to access resources. In fishes, jaw protrusion has been
 attributed to the massive diversity of suction-based feeding systems,
 facilitating the dominant mode of prey capture in this group. Nearly all
 fishes that feed by suction use upper jaw protrusion, achieved by rotation
 of the mandible at its base, which then transmits forward motion to
 independently mobile upper jaw bones. In this study, by contrast, we
 explore an unusual form of lower jaw protrusion in the freshwater
 invertivore, Nannocharax fasciatus, enabled by a novel intramandibular
 joint (IMJ). We combine morphological, kinematic, and biomechanical data
 to show that the added mobility created by the IMJ influences the pattern
 of suction-based prey capture movements and contributes to lower jaw
 protrusion (increasing it by 25%, based on biomechanical modeling).
 Interestingly, the upper jaw bones are fused in N. fasciatus and rotate
 about a single fixed joint, like the lower jaws of most other suction
 feeding fishes. We suggest that this vertical inversion of the jaw
 protrusion mechanism for ventrally directed suction-feeding on benthic
 prey is a likely exaptation, as the IMJ is used for biting in related
 taxa. This work highlights the ability of novelties to facilitate
 ecological specialization by enabling new functional capabilities.
description: # Suction feeding turned on its head: a functional novelty facilitates
 lower jaw protrusion
 [https://doi.org/10.5061/dryad.3j9kd51t1](https://doi.org/10.5061/dryad.3j9kd51t1) Data and R code associated with the following paper, published in Integrative and Comparative Biology: “Suction feeding turned on its head: a functional novelty facilitates lower jaw protrusion” Authors: Christopher M. Martinez (UC Irvine) Rizelle Mae M. Mazon (UC Irvine) Melanie L.J. Stiassny (American Museum of Natural History) Contact (Correspondence author): [c.martinez@uci.edu](mailto:c.martinez@uci.edu) (C.M.M) ## **Description of the data and file structure** The information below describes the contents of data files and code associated with this study: 1.     **video_info.txt**: table of length equal to the number of feeding motions, with the following columns: a.     *number*: integer specifying different feeding motions b.     *video*: file name of video associated with the feeding motion c.     *species_specimen*: the species and specimen number for each individual fish d.     *individual*: integer specifying individual fish identity e.     *max_gape_shape*: the frame (out of 20 total) at which the fish reached peak gape f.      *strike_duration_ms*: the total duration of the feeding movement in milliseconds g.     *scale_pixels_cm:* a scaling factor for landmark data in pixels per centimeter h.     *SL_mm:* standard length of the fish in millimeters i.      *t_peak_gape_ms:* the time to peak gape in milliseconds 2.     **jaw_bone_lengths.txt**: table of length equal to number of specimens with the following columns: a.     *specimen*: label with genus, species, and specimen identification number b.     *articular_mm*: length of the articular in millimeters c.     *dentary_mm*: length of the dentary in millimeters d.     *upper_jaw_joint_to_QMJ_mm*: distance from upper jaw joint to QMJ in millimeters e.     *articular_scaled*: articular length expressed as a proportion of column d f.      *dentary_scaled*: dentary length expressed as a proportion of column d g.     *Standard_length_mm*: standard length of the fish in millimeters 3.     **prey_acceleration.txt**: table with the following columns: a.     *video*: file name of video associated with the feeding motion b.     *species_specimen*: the species and specimen number for each individual fish c.     *specimen_num*: integer specifying individual fish identity d.     *video_num*: integer specifying video the data came from e.     *distance_cm:* Euclidean distance traveled by prey from the previous to current frame in centimeters f.      *distance_m:* Euclidean distance traveled by prey from the previous to current frame in meters g.     *time_ms:* elapsed time from initial frame that prey tracking begun in milliseconds h.     *time_s:* elapsed time from initial frame that prey tracking begun in seconds i.      prey_velocity_m_sec: velocity of prey movement from previous to current frame in meters per second 4.     **landmark_data.zip**: folder containing shape files for all feeding motions in this study. Each file contains cranial shape data taken from a single video frame. There are 2,180 total files. Collections of 20 files comprise a single feeding motion. Each file contains the x and y coordinates of cranial landmarks for the shape in question, with landmark labels provided. The file names contain the following information: Genus_species_specimen_video_frame (e.g., Nannocharax_fasciatus_01_002_0010). These data files are accessed by the R code in the file “Nannocharax_Martinez_et_al.R” and are needed to run that script. 5.     **sample_video.zip**: folder with the following contents: a.     *Nannocharax_fasciatus_05_040.avi:* sample high speed video (2,000 frames per second) b.     *Nannocharax_fasciatus_05_040_ruler.avi:* ruler file associated with the sample video c.     *Nannocharax_fasciatus_05_040_frames:* folder with 20 frames selected from sample video for motion analysis d.     *Nannocharax_fasciatus_05_040_landmarks:* folder with landmark data, which can be viewed in the Stereomorph package in R (see code file titled “motion_digitizing.R”). The file names contain the following information: Genus_species_specimen_video_frame (e.g., Nannocharax_fasciatus_05_040_0014). e.     *Motion_LMs.txt*: text file with list of landmarks needed to open landmarks in StereoMorph ## **Code/Software** 1.     **Nannocharax_Martinez_et_al.R**: code for preparing, plotting, and analyzing data from this study. 2.     **motion_digitizing.R:** code for viewing the digitized landmarks associated with 20 frames extracted from the sample video provided (*Nannocharax_fasciatus_05_040*)