Mucus secretion and transport in amphioxus larvae: organization and ultrastructure of the food trapping system, and implications for head evolution
Bibliographic record
Abstract
Abstract A low‐to‐medium power transmission electron microscopy survey of the larval head of amphioxus was used to re‐examine the position and constituent cell types of the mucus‐secreting organs involved in feeding. Previously unreported features include cells with fibril‐filled paraciliary processes in the recessed (pit) portion of the preoral organ, which probably assist in generating the mucus string produced by this structure, and the cell responsible for driving the current through the club‐shaped gland, which appears to depend on a mechanism analogous to Archimedes’ screw. Pharyngeal structures are dramatically repositioned during larval growth and metamorphosis. Mapping these changes shows that they are most easily explained if the positioning of the mouth is not directly controlled by the mechanism used to pattern the rest of the ventral pharynx. This accords with the predictions of the dorsoventral inversion hypothesis, which requires that an originally dorsal mouth in the inverted chordate ancestor be secondarily shifted to the ventral surface. It is argued here, on this basis, that the repositioning of the larval mouth in amphioxus, from the left side to the ventral midline, represents a partial recapitulation of past evolutionary events.
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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) | 0.000 | 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 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".