Life out of water: Genomic and physiological mechanisms underlying skin phenotypic plasticity
Bibliographic record
Abstract
Abstract The Devonian radiation of vertebrates from aquatic into terrestrial habitats required behavioral, physiological, and morphological adaptations. Changes to skin structure and function were likely crucial, but adaptations were needed to resolve contrasting demands of maintaining a mechanical and physiological barrier while also facilitating ion and gas transport. Little is known of the mechanisms that underlie skin plasticity and adaptation between water and air. We performed experiments using two isogenic lineages of an amphibious killifish ( Kryptolebias marmoratus from brackish and freshwater habitats) and used transcriptional and morphological data to reveal mechanisms recruited to resolve the dual challenges of skin providing both a barrier and an exchange interface during terrestrial acclimation. Transcriptional regulators of skin morphogenesis were quickly activated upon emersion. Regulation of cell-cell adhesion complexes, coupled with pathways homologous with those that regulate stratum corneum formation, was consistent with barrier function and mechanical reinforcement. Cutaneous respiration was associated with regulation of angiogenesis pathways and with blood vessel architecture that facilitated extremely short diffusion distances and direct delivery to ionocyotes. Evolutionary analyses revealed directional selection operating on proteins involved in barrier and respiratory functions, reinforcing the importance of these mechanisms for enabling the amphibious lifestyle of K. marmoratus . Fish from brackish niches were more resilient to emersion and also differed from freshwater fish in ionoregulatory responses to emersion. We conclude that plasticity of barrier, respiratory, and ionoregulatory functions in skin evolved to support the amphibious lifestyle of K. marmoratus ; similar processes may have facilitated the terrestrial radiation of ancient fishes. Significance statement The transition of vertebrate life from water to land coincided with solving multiple physiological challenges including avoiding drying out while also exchanging gases and ions with the environment. Though changes in the skin were likely important, little is known of the mechanisms that underlie skin flexibility and adaptation between water and air. We performed air exposure experiments with an amphibious killifish; gene expression profiling, microscopy, and evolutionary analysis of proteins revealed cell structures, proteins, and molecular pathways that support skin flexibility and adaptations during air exposure, and ion regulation contributed to differences in killifish abilities to adjust to air. Amphibious killifish are useful models to help us understand changes that enable water to air transitions in contemporary and ancient fishes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".