Skeletal stiffening in an amphibious fish out of water is a response to increased body weight

• DOI: 10.1242/jeb.161638
• Publication Date: 2017-10-18T21:25:23Z
• Authors: Andy J. Turko; Dietmar Kültz; Douglas Fudge; Roger P. Croll; Frank M. Smith; Matthew R. Stoyek; Patricia A. Wright
• Keywords: Tetrapod (structure); Stiffening

Terrestrial animals must support their bodies against gravity, while aquatic are effectively weightless because of buoyant from water. Given this evolutionary history minimal gravitational loading fishes in water, it has been hypothesized that weight-responsive musculoskeletal systems evolved during the tetrapod invasion land and thus absent fishes. Amphibious fishes, however, experience increased effective weight when out water - these responsive to loading? Contrary tetrapod-origin hypothesis, we found terrestrial acclimation reversibly gill arch stiffness (∼60% increase) amphibious fish Kryptolebias marmoratus loaded normally by but not under simulated microgravity. Quantitative proteomics analysis revealed change mechanical properties occurred via abundance proteins responsible for bone mineralization other as well tetrapods. Type X collagen, associated with endochondral growth, almost ninefold after acclimation. Collagen isoforms known promote extracellular matrix cross-linking cause tissue stiffening, such types IX XII also abundance. Finally, more densely packed collagen fibrils both arches filaments were observed microscopically terrestrially acclimated fish. Our results demonstrate system can be fine-tuned response changes body using biochemical pathways similar those mammals, suggesting sensing is an ancestral vertebrate trait rather than a innovation.