Bibliographic record
Abstract
Asking the right questions about evolution of development, larval morphology, and life history requires knowledge of ancestral state. Two hypotheses dominate current opinion about the ancestral life cycle of bilaterians: the "larva-first" and the "intercalation" hypotheses. Until recently, the larva-first hypothesis was preeminent. This proposes that the original indirect life cycle of bilaterians included a planktotrophic larva followed by a benthic adult. Phylogenetic evidence suggests that a planktotrophic larva is plesiomorphic for echinoderms. A preponderance of developmental studies on echinoderms may have fostered a tendency to extrapolate conclusions about echinoderm development to other clades, particularly the concept that larval and juvenile/adult bodies are mostly separate entities. However, some of the recent reconstructions of bilaterian phylogeny suggest that nonfeeding larvae may have been ancestral for bilaterians, and these may have been intercalated into a life cycle that was originally direct. I review comparative data on molluscan development that suggests the trochophore-like stage is little more than a gastrula with transient structures (prototroch and apical sensory organ) to allow a temporary planktonic phase during development. Most lineage founder cells of molluscan embryos generate progeny that develop through the veliger stage into structures of the juvenile, which becomes benthic when the prototroch and apical sensory organ are lost. In light of this, the model of separate larval and juvenile bodies with the latter developing from nests of multipotent cells within the larva is inappropriate for molluscs. The intercalation hypothesis may be a better model for interpreting development of molluscs and other lophotrochozoans.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".