Epithelia, an Evolutionary Novelty of Metazoans
Why this work is in the frame
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Bibliographic record
Abstract
At the point in animal evolution when cells began to adhere to each other they presumably initially functioned as colonies. The formation of an epithelium that enclosed and controlled an internal milieu would have been the first event to distinguish an individual animal from a colony. To better understand when the first epithelium arose and what its characteristics were, we evaluate the morphological, functional, and molecular characters of epithelia in sponges, considered here the extant representatives of the first metazoans. In particular, we show new claudin-like sequences from sponges align most closely with sequences from Drosophila that have a barrier function in septate junctions. We also show that type IV collagen, the main component of the basement membrane (BM), is present in calcareous sponges, and we confirm the presence of type IV-like collagen (spongin short chain collagen) in other sponges. Though in sponges as in other metazoans the epithelium has grades of specialization with varying complexity of junctions and the BM, the main character of a functional epithelium, the ability to seal and control the ionic composition of the internal milieu, is a property of even the simplest sponge epithelium, and therefore the first metazoans likely also had epithelia with these characteristics, which we consider a "true" epithelium.
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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 it