Inflated protoconchs and internally dissolved, coiled protoconchs of nudibranch larvae: different developmental trajectories achieve the same morphological result
Bibliographic record
Abstract
Abstract. Light and scanning electron microscopy were used to examine protoconch form in eight species of planktotrophic heterobranch larvae, including four nudibranch species with a coiled (type 1) protoconch, two nudibranch species with an inflated (type 2) protoconch, and two cephalaspid species with a coiled protoconch. The coiled protoconchs of the cephalaspids and nudibranchs have a similar form at hatching, and shell growth up to metamorphic competence is hyperstrophic. Shell added to coiled protoconchs during the larval stage overgrows all but the left wall of the initial protoconch that exists at hatching. The entire protoconch of cephalaspids, including overgrown areas, is retained through metamorphosis. However, during later larval development in nudibranchs with a coiled protoconch, overgrown shell is completely removed by dissolution. As a result, regardless of whether nudibranch larvae hatch with an inflated or coiled protoconch type, the protoconch is a large, hollow cup at metamorphic competence. The protoconch of nudibranchs is shed at metamorphosis and absence of a post‐metamorphic shell is correlated with absence of visceral coiling in this gastropod group. Internal dissolution of the coiled protoconch in nudibranchs allows the left digestive gland to uncoil prior to metamorphic shell loss. Retention of overgrown protoconch whorls in cephalaspids allows the attachment plaque of the pedal muscle to migrate onto the parietal lip of the post‐metamorphic shell. Release from this constraint in nudibranchs, in which the larval pedal muscles and the entire protoconch are lost at metamorphosis, may have permitted internal protoconch dissolution and precocious uncoiling of the visceral mass, as well as evolutionary emergence of the inflated larval shell type.
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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".