Modification of pectoral fins occurs during the larva-to-juvenile transition in the mudskipper (Periophthalmus modestus)

Eri Okamoto,Mikiko Tanaka,Atsushi Ishimatsu,Hieu Van Mai

doi:10.1186/s40851-018-0105-z

Eri Okamoto, Mikiko Tanaka + Show 2 more

Open Access

https://doi.org/10.1186/s40851-018-0105-z

Copy DOI

Abstract

BackgroundMudskippers are amphibious fishes that use their pectoral fins to move on land. Their pectoral fins are specifically modified for terrestrial locomotion. Studies of the anatomy and kinematics of adult mudskippers suggest that modifications of the pectoral fins, such as their protrusion and elongation of the proximal radials, may provide greater control and flexibility in pectoral fin–based locomotion. However, it is unknown when and how the unique features of these pectoral fins form during the development of mudskippers, which begin life as a planktonic organism.ResultsHere we examined the developmental process of the pectoral fins of the mudskipper Periophthalmus modestus to address these questions. We also observed other developmental characteristics to provide clarified descriptions, including indicative morphological changes that occur during metamorphosis.ConclusionOur results show that the localized cell division of the proximal part of the endoskeletal disc—the primordium of the proximal radials—and subsequent cell division along the proximal-distal axis, which is restricted to the distal part of the disc during the larva-to-juvenile transition (metamorphosis), lead to the elongation of the proximal radials.

Highlights

Mudskippers are amphibious fishes that use their pectoral fins to move on land
Our results show that the localized cell division of the proximal part of the endoskeletal disc, which is the primordium of the proximal radials, and subsequent cell divisions of chondrogenic cells along the proximal-distal axis only in its distal region during the larva-to-juvenile transition lead to the elongation of the proximal radials
Remodeling of the endoskeletal disc In this study, we found that the shape of the endoskeletal disc transforms from elliptical (Fig. 7e) to fanshaped (Fig. 7f ) during metamorphosis from larvae (7.9 mm TL) to juveniles (13.6 mm TL) in the mudskipper Ps. modestus, which corresponds to the larvato-juvenile transition

Summary

Introduction

Mudskippers are amphibious fishes that use their pectoral fins to move on land. Their pectoral fins are modified for terrestrial locomotion. Studies of the anatomy and kinematics of adult mudskippers suggest that modifications of the pectoral fins, such as their protrusion and elongation of the proximal radials, may provide greater control and flexibility in pectoral fin–based locomotion. It is unknown when and how the unique features of these pectoral fins form during the development of mudskippers, which begin life as a planktonic organism. Endoskeletal elements of the pectoral fins of Periophthalmus exhibit unique morphological characteristics [2, 3]; the proximal radials are more elongated and protrude farther from the body wall than in other gobies [2] This unique skeletal pattern allows the creation of two movable hinge joints at the boundaries between the

Methods

Results

Discussion

Conclusion