Convergent latitudinal erosion of circadian systems in a rapidly diversifying order of fishes
Bibliographic record
Abstract
Biological clocks allow organisms to anticipate cyclical environmental changes, yet in high-latitude or deep-sea habitats, the diel cues that entrain these rhythms are often seasonally diminished or absent. Fishes of the order Perciformes have rapidly diversified across these arrhythmic ecosystems, raising the question of whether changes to circadian rhythms and biological clock genetic architecture are a component of their evolutionary success. Here, we used a comparative genomic approach to investigate patterns of core biological clock gene loss across 96 perciform and five outgroup species. We found widespread and lineage-specific loss in core clock genes, particularly in the convergently evolving polar and deep-sea suborders Notothenioidei and Cottoidei. This trend of clock gene loss was significantly amplified with higher-latitude species. To determine if these genomic signatures reflect a functional loss of rhythmicity, we performed metabolic phenotyping on three notothenioid species. We found a consistent lack of circadian metabolic oscillations during the late austral fall across all notothenioids, including the sub-Antarctic sister lineage to the cryonotothenioid adaptive radiation, Eleginops maclovinus. Experimental data across Perciformes, combined with suborder-wide patterns of gene loss, suggest that a release from circadian constraints occurred early in their diversification, potentially facilitating the repeated expansion of these fishes into polar and deep-sea habitats.
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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 | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".