Elucidating the function of the enigmatic fish pseudobranch using transcriptomics. Novel expression of the Na+/H+-exchanger 5.
Bibliographic record
Abstract
In fishes, the fish pseudobranch is the paired, small hemibranchs of mandibular arch-derived gill tissue. Each pseudobranch receives oxygenated arterial blood and the efferent blood travels to the eyes. In the Nile tilapia (Oreochromis niloticus), the pseudobranch is fully embedded without any freely exposed gill filaments to the water which precludes the typical gill function of gas exchange. The pseudobranch parenchyma cells are rich in mitochondria and have a tubular system similar to gill ionocytes indicating a high metabolic capacity. Despite being identified over 200 years ago, the pseudobranch has remained enigmatic. One hypothesis regarding its function is that it acidifies the blood to aid in oxygen unloading (Root shift) to aid eye oxygen delivery; however, supporting physiological data is lacking. In the present study we used RNAseq to characterize the gene repertoire of the pseudobranch by contrasting expression with gill tissue. We identified 2621 higher and 2502 lower expressed genes (|FC| > 2 p<0.05; PBr:Gill). This notably included higher pseudobranch expression of genes involved in the pentose phosphate shunt, and lactate metabolism as well as ion transport gene isoform differences (eg Na+/K+-ATPase α1a is higher in gill and α1b in pseudobranch). Transporters involved in Na+ uptake (nhe2, ncc2) were higher in gill too. However, the nhe5 was very highly expressed in pseudobranch and using immunohistochemistry Nhe5 was localized to the pillar cells (specialized endothelial cells) of the pseudobranch but not the gills. Together, these results suggest that in tilapia the pseudobranch may be involved in blood acidification.
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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".