DOI: 10.5061/dryad.np5hqc028
title: Data from: Biphasic burrowing in Atlantic hagfish (Myxine limosa)

description: Myxine limosa is a burrowing species of hagfish that occurs in the western
 north Atlantic in areas with muddy substrate and at depths generally
 greater than 100 meters. Burrowing of M. limosa has been observed from
 submersibles, but little is known about the behavior of these animals
 within the substrate or the biomechanical mechanisms involved. Here we
 investigated burrowing in M. limosa by observing individuals as they
 burrowed through transparent gelatin. A photoelastic setup using crossed
 polarizers allowed us to visualize stress development in the gelatin as
 the hagfish moved through it. We found that M. limosa created U-shaped
 burrows in gelatin using a stereotyped, two-phase burrowing behavior. In
 the first (“Thrash”) phase, hagfish drove their head and their anterior
 body into the substrate using vigorous sinusoidal swimming movements, with
 their head moving side-to-side. In the second (“Wriggle”) phase, swimming
 movements ceased, with propulsion coming exclusively from the anterior,
 submerged portion of body. The Wriggle phase involved side-to-side head
 movements and movements of the submerged part of the body that resembled
 the “internal concertina” strategy used by caecilians and uropeltid
 snakes. The entire burrowing process took on average 7.6 minutes to
 complete and ended with the hagfish’s head protruding from the substrate
 and the rest of its body generally concealed. Understanding the burrowing
 activities of hagfishes could lead to improved understanding of sediment
 turnover in marine benthic habitats, new insights into the reproductive
 behavior of hagfishes, or even inspiration for the design of burrowing
 robots.
description: # Biphasic burrowing in Atlantic hagfish (Myxine limosa)
 [https://doi.org/10.5061/dryad.np5hqc028](https://doi.org/10.5061/dryad.np5hqc028) Data for paper on burrowing biomechanics of Atlantic hagfish (Myxine limosa) ## Description of the data and file structure **Worksheet: Tables 1 & 2** Trial Name – Name for each burrowing video used in the study (includes the date recorded) Chamber – indicates which of the three sizes of chambers were used during this recording (small, medium, large). Polarizing – Some trials were conducted using a photoelastic setup (crossed polarizers on either side of the chamber, with illumination from behind). This column indicates if polarizing films were used. Time when tail stops (H:MM:SS) – Time on recording when the Hagfish stopped tail thrashing while burrowing (when the Hagfish transitioned from phase 1 to phase 2). Phase1Duration (H:MM:SS) – Duration of the Phase 1 calculated as (Time when tail stops) – (Burrow Start Time). Phase 1 Duration (s) – Phase 1 duration converted to seconds. Phase 2 Interval (H:MM:SS) Duration of phase 2 of the burrow calculated as (Burrow End Time) – (Time when tail stops). Phase 2 Interval (s) – Phase 2 interval converted to seconds. Burrow Start Time (H:MM:SS) – Time on the recording when the Hagfish began burrowing. Burrow End Time (H:MM:SS) – Time on the recording when the Hagfish stopped burrowing or broke through the gelatin. Burrow Duration (H:MM:SS) – Total time in burrow calculated as (Burrow End Time) – (Burrow Start Time). Burrow Duration (s) – Burrow duration converted to seconds. HF Length (px) – Body Length of the Hagfish in pixels. HF Length (cm) – HF Length converted to cm using the Calibration. Calibration (px/cm) – The Calibration was obtained on ImageJ by measuring the width of the chamber in pixels which was already measured for each chamber in cm. The calibration was used to convert measurements in px to cm. Hole Depth (px) – Distance in pixels of the primer hole the hagfish began its burrow into. Hole Depth (cm) – Hole Depth (px) converted to cm using the Hole Depth Calibration. BurrowDistance (px) – Distance in pixels of the total burrow distance measured by Image J. BurrowDistance (cm) – Burrow Distance (px) converted to cm using Calibration. RelBurrowDistance – Burrow Distance as a fraction of body length calculated by dividing the Burrow Distance (cm) by the Hagfish Length (cm). TransitionDepth (px) – Distance between the lowest point of the Hagfish and the top of the gelatin (in pixels) at the Time when tail stops (when the hagfish transitions from phase 1 to phase 2). TransitionDepth (cm) – Transition Depth (px) converted to cm using the Calibration. RelativeTransDepth – Transition Depth as a fraction of body length calculated by dividing the Transition Depth (cm) by the Hagfish Length (cm). TransitionLegnth (px) - Length of the Hagfish body (in pixels) in the gelatin at the Time when tail stops (when the hagfish transitions from phase 1 to phase 2). TransitionLength (cm) – Transition Length (px) converted to cm using the calibration. TransitionL-HoleL (cm) – represents the adjusted transition length after factoring in the hole length. Phase1 V NotAdj – This variable represents the velocity of the hagfish during phase 1 by using the transition length as the distance and phase 1 duration as the time. Adj Phase1Velocity (cm/min) – This variable represents the adjusted velocity of the hagfish during phase 1 by using the TransitionL-HoleL as the distance and phase 1 duration as the time. Phase2Length (cm) – This distance represents the distance burrowed by the hagfish during phase 2. Phase2Velocity (cm/min) – This variable represents the velocity of burrowing by the hagfish during phase 2 of the burrow. Overal Velocity NoAdj (cm/mi) – This variable represents the velocity of the whole burrowing event calculated by dividing the Burrow Distance (cm) by the Burrow Duration (min). RelativeTransLength – Transition length as a fraction of the body length. It is calculated by dividing the Transition length (cm) by the HF Length (cm). MaxDepth_px – Distance, measured in pixels, between the lowest point of the hagfish burrow and the top of the gelatin. MaxDepth (cm) – Max Depth (px) converted to cm by using the calibration. RelativeDepth – Max depth as a fraction of the Hagfish body length by dividing Max Length (cm) by the HF Length (cm). TailExposure (px) - Length of the tail, measured in pixels, above the gelatin at time equal to Burrow End. TailExposure (cm) – TailExposire (px) converted to cm by using the calibration. RelTailExposure – Tail Exposure as a fraction of body length by dividing Tail Exposure (cm) by HF Length (cm). HorizDistance (px) – Distance, measured in pixels, between the left most point of the Hagfish and the right most point of the Hagfish at the end of the burrow. HorizDistance (cm) – HorizDistance (px) converted to cm by using the calibration. RelHorizDistance – HorizDistance measured as a fraction of body length by dividing the HorizDistance (cm) by the HF Length (cm). **Explanation of blank cells from Oct_26_2021 trial:** During the recording of this trial, footage stopped (due to a battery malfunction) while the hagfish was burrowing horizontally along the bottom of the chamber. Because the whole burrow was not recorded, we were not able to obtain Burrow Duration (and all variables which are calculated using Burrow Duration), Burrow Distance (and all variables calculated using Burrow Distance), Tail Exposure, and Horizontal Distance. However, the first half of the Burrow was fully recorded and as a result the rest of the relevant variables were able to be measured. **N.B. re: Phase 1 and Phase 2 nomenclature:** In the manuscript, we changed the name of the two phases from Phase 1 and Phase 2 to Thrash and Wriggle phases, respectively, based on a reviewer suggestion. **Worksheet: Fig 6** These are data from the detailed analysis of progress into a burrow of one hagfish that was ideally positioned to measure this. Obs – denotes the observation number (each observation came from analyzing a single frame of video) Frame – is the video frame number Time – is the time elapsed since the first frame calculated using the frame rate (60 fps) Length (px) – distance (in pixels) between the tip of the tail and a fixed location on the burrow chamber (middle of the silver dot with the thin horizontal line, indicated in the L panel of Fig. 6) Length (cm) – distance converted to cm using the calibration (15.141 px/cm) Progress (cm) – cumulative progress into burrow calculated as the difference between the initial exposed tail length and the exposed tail length at the time of measurement Velocity (px/s) – velocity measured as the slope of the length(px) and time columns Velocity (cm/s) - velocity measured as the slope of the progress(cm) and time columns Velocity (cm/min) - velocity converted to cm/min by measuring value in cm/sec by 60. Calibration – calibration value obtained by measuring a known distance (chamber width) in pixels using ImageJ. **Worksheet: Pausing Data** Data for measuring the frequency and duration of pauses during burrowing bouts for all trials. Trial name – self explanatory, contains date trial was completed Duration before burrow starts  Time when tail stops  Pause 1 Start – time when the first pause began Pause 1 Stop – time when the first pause ended Pause 1 Duration – calculated by subtracting Pause 1 Stop from Pause 1 Start Pause 2, 3, 4 columns – same as above (max number of pauses observed was 4) Number of pauses – self explanatory Total Pause Time – sum of all the Pause Durations. **Worksheet: Fig S1** Data from four photoelastic burrowing trials in which the proportion of the body engaged in concertina movements was measured. Total BL(pixels) – length of hagfish measured from tip of tail to tip of head in pixels Time – timestamp of where measurements were made (9 measurements made for each analyzed trials) BL in gel (px) -  length of the body immersed in the gelatin in pixels BL concertina (px) – length of the body engaged in concertina in pixels BL % in gel – proportion of the body immersed in the gelatin as a percentage of total body length BLconc% - proportion of the body engaged in concertina as a percentage of total body length ## Code/Software Code for midline analysis is available at: [https://github.com/CDonatelli/HagfishBurrowing](https://github.com/CDonatelli/HagfishBurrowing)