Closer to the Heart: Cardiac Muscle Aerobic Capacity Correlates With Intraspecific Variation in Sprint Performance Rather Than Androgen Levels in the Neotropical Lizard <i>Tropidurus catalanensis</i>
Bibliographic record
Abstract
Assessments of the interplay between physiology and whole-organism performance are fundamental to understand how individuals function in different ecological contexts. Here, we investigated the relationship between locomotor performance, androgen levels, and metabolic capacity of muscle tissues in the lizard Tropidurus catalanensis. We hypothesized that faster individuals would exhibit higher circulating androgen concentrations and greater metabolic capacity in skeletal and cardiac muscles, regardless of body size. We measured morphological variables, maximum sprint speed (v), plasma testosterone concentration, and the maximum activity of the enzymes lactate dehydrogenase (LDH) and citrate synthase (CS) in the gastrocnemius, iliofibularis, and cardiac muscles of adult males. We found that intraspecific variations in v were not explained by body size, plasma testosterone concentration, nor by the activity of LDH or CS in skeletal muscles. The absence of an effect of testosterone on locomotion suggests that androgen concentrations may change in response to other factors, such as environmental stressors or reproductive state. Our results indicated that the fastest lizards also had the highest CS activity in the heart. This relationship suggests that cardiac oxidative capacity plays an important role in clearing metabolites in the postexercise recovery phase. We also found a positive relationship between CS and LDH in all tissues, suggesting a functional complementarity between glycolytic and aerobic pathways that should be relevant in situations that require rapid alternation between bursts of speed and endurance, such as predator evasion or thermoregulation. Ultimately, our results highlight the importance of integrating performance and physiological traits to understand interactions between animals and their environment.
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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 | 0.000 |
| 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".