DOI: 10.5061/dryad.sqv9s4n99
title: Anatomical insights into fish terrestrial locomotion: a study of barred mudskipper (Periophthalmus argentilineatus) fins based on μCT 3D reconstructions

description: Mudskippers are a group of extant ray-finned fishes with an amphibious
 lifestyle and serve as exemplars for understanding the evolution of
 amphibious capabilities in teleosts. A comprehensive anatomical profile of
 both the soft and hard tissues within their propulsive fins is essential
 for advancing our understanding of terrestrial locomotor adaptations in
 fish. Despite the ecological significance of mudskippers, detailed data on
 their musculoskeletal anatomy remains limited. In the present research, we
 utilized contrast-enhanced high-resolution micro-computed tomography (μCT)
 imaging to investigate the barred mudskipper, Periophthalmus
 argentilineatus. This technique enabled detailed reconstruction and
 quantification of the morphological details of the pectoral, pelvic, and
 caudal fins of this terrestrial mudskipper, facilitating comparison with
 its aquatic relatives. Our findings reveal that P.
 argentilineatus has undergone complex musculoskeletal adaptations for
 terrestrial movement, including an increase in muscle complexity and
 muscle volume, as well as the development of specialized structures like
 aponeuroses for pectoral fin extension. Skeletal modifications are also
 evident, with features such as a reinforced shoulder-pelvic joint and
 thickened fin rays. These evolutionary modifications suggest
 biomechanically advanced fins capable of overcoming the gravitational
 challenges of terrestrial habitats, indicating a strong selective
 advantage for these features in land-based environments. The
 unique musculoskeletal modifications in the fins of mudskippers like P.
 argentilineatus, compared to their aquatic counterparts, mark a critical
 evolutionary shift toward terrestrial adaptations. This study not only
 sheds light on the specific anatomical changes facilitating this
 transition but also offers broader insights into the early evolutionary
 mechanisms of terrestrial locomotion, potentially mirroring the
 transformative journey from aquatic to terrestrial life in the lineage
 leading to tetrapods.
description: Specimens were
 collected from Okinawa Island, Japan, complemented by a zebrafish acquired
 from a local pet shop. Following humane euthanization with
 2-phenoxyethanol, they were preserved first in 10% formalin and then
 stored in ethanol to maintain their integrity for scanning. Before
 micro-CT scanning, each specimen was stained with an iodine-based solution
 to enhance soft tissue contrast, thereby improving scan visibility.
 High-resolution micro-CT scans were then performed using a Zeiss Xradia
 Versa 510 at the Okinawa Institute of Science and Technology, ensuring
 detailed visualization of each specimen's anatomical
 structure.<br> To visualize the fins' skeletal and
 muscular structures and their locomotion functions, we developed an
 animated video. This entailed exporting segmented bone and muscle models
 in *.stl format from segmentation software into Blender for 3D animation.
 We programmed the animation sequence with Python in Blender's API,
 showcasing the muscle groups, movements, and transitions, complemented by
 manual camera animation to enhance feature visibility. Additionally,
 legends and labels were integrated into the animation using Python
 scripting and vector math for accurate placement. The animation was
 finalized and rendered clear with ffmpeg, providing a vivid representation
 of our findings. The final video was rendered and compiled using the
 ffmpeg program.
description: # Anatomical insights into fish terrestrial locomotion: a study of barred
 mudskipper (*Periophthalmus argentilineatus*) fins based on μCT 3D
 reconstructions This dataset comprises high-resolution micro-CT image
 series from five unique raw datasets representing distinct fish species:
 three aquatic gobies, a zebrafish, and one mudskipper, *Periophthalmus
 argentilineatus*. Designed to showcase the complete anatomical structures
 of these species, the dataset focuses on external and internal
 morphologies. Manual segmentation was applied to the fins (pectoral,
 pelvic, and caudal). The resulting visualizations can be found in the
 manuscript. ### Description of data and file structure Data were obtained
 via microCT (Zeiss Xradia Versa 510) and are stored in DICOM format. Each
 species' dataset has been compressed into an RAR archive, labeled
 with the species name and its size (total length in millimeters).
 Open-source DICOM viewers can be used to access this data. Additionally,
 the dataset includes an animated video (in mp4 format) showcasing the
 segmented models. This video is compatible with standard video software,
 including a VLC media player. ### Sharing/Access information This dataset
 is unique and exclusively available through this submission.