Physiological tradeoffs may underlie the evolution of hypoxia tolerance and exercise performance in sunfish (Centrarchidae)
Bibliographic record
Abstract
Tradeoffs between hypoxia tolerance and aerobic exercise performance appear to exist in some fish taxa, even though both of these traits are often associated with a high O2 transport capacity. We examined the physiological basis for this potential tradeoff in four species of sunfish from the family Centrarchidae. Hypoxia tolerance was greatest in rock bass, intermediate in pumpkinseed and bluegill and lowest in largemouth bass, based on measurements of critical O2 tension (Pcrit) and O2 tension at loss of equilibrium (PO2 at LOE). Consistent with there being a tradeoff between hypoxia tolerance and aerobic exercise capacity, the least hypoxia-tolerant species had the highest critical swimming speed (Ucrit) during normoxia and suffered the greatest decrease in Ucrit in hypoxia. There was also a positive correlation between Ucrit in normoxia and PO2 at LOE, which remained significant after accounting for phylogeny using phylogenetically independent contrasts. Several sub-organismal traits appeared to contribute to both hypoxia tolerance and aerobic exercise capacity (reflected by traits that were highest in both rock bass and largemouth bass), such as the gas-exchange surface area of the gills, the pH sensitivity of haemoglobin-O2 affinity, and the activities of lactate dehydrogenase and the gluconeogenic enzyme phosphoenolpyruvate carboxykinase in the liver. Some other sub-organismal traits were uniquely associated with either hypoxia tolerance (low sensitivity of haemoglobin-O2 affinity to organic phosphates, high pyruvate kinase and lactate dehydrogenase activities in the heart) or aerobic exercise capacity (capillarity and fibre size of the axial swimming muscle). Therefore, the cumulative influence of a variety of respiratory and metabolic traits can result in physiological tradeoffs associated with the evolution of hypoxia tolerance and aerobic exercise performance in fish.
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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 | 0.000 | 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".