Coronal organ of ascidians and the evolutionary significance of secondary sensory cells in chordates
Bibliographic record
Abstract
A new mechanoreceptor organ, the coronal organ, in the oral siphon of some ascidians belonging to the order Pleurogona has recently been described. In contrast to the known mechanoreceptor organs of ascidian atrium that consist of sensory neurons sending their own axons to the cerebral ganglion, coronal sensory cells are secondary mechanoreceptors, i.e., axonless cells forming afferent and efferent synapses with neurites of neurons located in the ganglion. Moreover, coronal cells exhibit an apical apparatus composed of a cilium accompanied or flanked by rod-like microvilli (stereovilli). Because of the resemblance of these cells to vertebrate hair cells, their ectodermal origin and location in a linear array bordering the bases of the oral tentacles and velum, the coronal organ has been proposed as a homologue to the vertebrate acousticolateralis system. Here we describe the morphology of the coronal organs of six ascidians belonging to the suborders Phlebobranchia and Aplousobranchia (order Enterogona). The sensory cells are ciliated, lack typical stereovilli, and at their bases form synapses with neurites. In two species, the sensory cells are accompanied by large cells involved in synthesis and secretion of protein. We hypothesize that the coronal organ with its secondary sensory cells represents a plesiomorphic feature of ascidians. We compare the coronal organ with other chordate sensory organs formed of secondary sensory cells, i.e., the ventral lip receptors of appendicularians, the oral secondary sensory cells of cephalochordates, and the acousticolateralis system of vertebrates, and we discuss their homologies at different levels of organization.
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How this classification was reachedexpand
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 | 0.002 |
| 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 teacher head, 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".