Characterization of mechanisms for Ca2+ and HCO3–/CO32– acquisition for shell formation in embryos of the freshwater common pond snail <i>Lymnaea stagnalis</i>
Bibliographic record
Abstract
The freshwater common pond snail Lymnaea stagnalis produces embryos that complete direct development, hatching as shell-bearing individuals within 10 days despite relatively low ambient calcium and carbonate availability. This development is impaired by removal of ambient total calcium but not by removal of bicarbonate and/or carbonate. In this study we utilized pharmacological agents to target possible acquisition pathways for both Ca(2+) and accumulation of carbonate in post-metamorphic, shell-laying embryos. Using whole egg mass flux measurements and ion-specific microelectrode analytical techniques, we have demonstrated that carbonic anhydrase-catalyzed hydration of CO(2) is central in the acquisition of both shell-forming ions because it provides the hydrogen ions for an electrogenic vacuolar-type H(+)-ATPase that fuels the uptake of Ca(2+) via voltage-dependent Ca(2+) channels and possibly an electrogenic Ca(2+)/1H(+) exchanger. Additionally, CO(2) hydration provides an endogenous source of HCO(3)(-). Thus, hydration of endogenous CO(2) forms HCO(3)(-) for calcification while hydrogen ions are excreted, contributing to continued Ca(2+) uptake, as well as creating favorable alkaline internal conditions for calcification. The connections between Ca(2+) and HCO(3)(-) acquisition mechanisms that we describe here provide new insight into this efficient, embryonic calcification in freshwater.
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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) | 0.000 | 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 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".