Changes in ventilation, metabolism, and behaviour, but not bradycardia, contribute to hypoxia survival in two species of Amazonian armoured catfish
Bibliographic record
Abstract
Amazonian armoured catfishes exhibit substantial cardiac hypoxia tolerance, but little is known concerning organismal cardiorespiratory, metabolic, and behavioural responses to low oxygen levels. This study assessed the general mechanisms used by two species of armoured catfish, Glyptoperichthyes gibbceps and Liposarcus pardalis, to survive the frequent periods of hypoxia encountered in the Amazon River. The gill ventilation rate (fv) and heart rate (fh) were studied under controlled hypoxia in aquaria and under natural hypoxia in a simulated pond. Glyptoperichthyes gibbceps were fitted with radiotelemetry tags and held in field cages to study their habits of depth selection and air breathing. When denied aerial respiration under hypoxia in aquaria, G. gibbceps increased fv, but neither they nor L. pardalis exhibited alterations in fh. An increase in fvwas initially observed in G. gibbceps during pond hypoxia before aerial respiration was initiated and fvdeclined. Glyptoperichthyes gibbceps were hyperglycaemic under normoxia, and extremely large increases in plasma glucose and lactate concentrations were observed under hypoxia. Field studies confirmed their nocturnal behaviour and showed that air breathing increased at night, regardless of dissolved oxygen concentration. Our results show that armoured catfishes preferentially up-regulate fvand anaerobic metabolism and exhibit no bradycardia during hypoxia.
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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) | 0.001 | 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".