Hemoglobin enhances oxygen uptake in larval zebrafish (<i>Danio rerio</i>) but only under conditions of extreme hypoxia
Bibliographic record
Abstract
The role of hemoglobin (Hb) in O(2) uptake by zebrafish larvae ranging in age from 5 to 42 days postfertilization was assessed under conditions of normoxia, moderate hypoxia and extreme hypoxia. This was achieved by exposing larvae with and without functional Hb to continuously declining oxygen levels (P(O(2))) in closed-system respirometers. Exposure to 5% CO for 2-4 h was used to render Hb effectively non-functional in terms of its ability to transport O(2). Routine metabolic rate (rM(O(2))), critical dissolved oxygen level (P(c)) and residual oxygen level (P(r)) were determined and used, respectively, as indicators of response in normoxia, moderate hypoxia and extreme hypoxia. rM(O(2)) was defined as the average rate of O(2) uptake before O(2) became limiting (i.e. at high P(O(2))s). P(c) is the P(O(2)) at which rM(O(2)) first becomes O(2)-limited and P(r) is the P(O(2)) below which larvae are no longer able to extract O(2) from the ambient medium. CO poisoning had no significant impact on rM(O(2)) or P(c) at any age, indicating that the lack of functional Hb does not impair routine O(2) usage in normoxia or at moderate levels of hypoxia [down to at least 25-50 torr (1 torr approximately 0.133 kPa), depending on age]. P(r), however, was significantly lower overall for control larvae (6.7+/-1.1 torr; mean +/- 95%CI) than for CO-poisoned larvae (11.2+/-2.1 torr). It would appear that the presence of functional Hb allows zebrafish larvae to extract O(2) from water down to lower P(O(2))s under conditions of extreme hypoxia. This is the first documented (as opposed to inferred) benefit of Hb in developing zebrafish. However, given the relatively small magnitude of the effect it is unclear if this benefit on its own is sufficient to balance the costs associated with Hb production and maintenance.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".