ATP and glutamate coordinate contractions in the freshwater sponge <i>Ephydatia muelleri</i>
Bibliographic record
Abstract
Abstract Sponges (phylum Porifera ) are an early diverging animal lineage that lacks both conventional nervous and muscular systems, and yet they are able to produce coordinated whole-body contractions in response to disturbances. Little is known about the underlying signaling mechanisms in coordinating such responses. Previous studies demonstrated that sponges respond specifically to neuroactive chemicals such as L-glutamate and γ-amino-butyric acid (GABA), which trigger and prevent contractions respectively. Genes for purinergic P2X-like receptors are present in several sponge genomes, leading us to ask whether ATP works with glutamate to coordinate contractions in sponges as it does in other animal nervous systems. Using pharmacological approaches on the freshwater sponge Ephydatia muelleri , we show that ATP is involved in coordinating contractions. Bath applications of ATP cause a rapid, sustained expansion of the excurrent canals in a dose-dependent manner. Complete contractions occur when ATP is added in the presence of apyrase, an enzyme that hydrolyzes ATP. Applying ADP, the first metabolic product of ATP hydrolysis, triggers complete contractions, whereas AMP, the subsequent metabolite, does not trigger a response. Blocking ATP from binding and activating P2X receptors with pyridoxalphosphate-6-azophenyl-2’,4’-disulfonic acid (PPADS) prevents both glutamate- and ATP-triggered contractions, suggesting that ATP works downstream of glutamate. Bioinformatic analysis revealed two P2X receptor sequences, one which groups with other vertebrate P2X receptors. Altogether, our results confirm that purinergic signaling by ATP is involved in coordinating contractions in the freshwater sponge suggesting a role of ATP-mediated signaling that predates the evolution of the nervous system and multicellularity in animals. Summary statement Nerveless sponges coordinate a sneeze-like reflex using glutamate and ATP signaling to expel water from the body.
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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".