Through the Looking-Glass: Shell Morphology, Anatomy and Mating Behavior of Reversed Pomacea Canaliculata (Caenogastropoda, Ampullariidae)
Bibliographic record
Abstract
Snails exhibit a primary left-right asymmetry that appears during the first cleavages of the eggs, and a secondary asymmetry, related to the coiling of the shell. Most species are constituted by either dextral or sinistral morphs (enantiomorphs) while individuals with reversed primary asymmetry are extremely rare. Freshwater snails of the family Ampullariidae are normally dextral enantiomorphs with planispiral, hyperstrophic or orthostrophic shells. Pomacea canaliculata, a well-studied species because of its invasive status, shows dextral primary asymmetry and orthostrophic growth that results in clock-wise shells. Despite the great number of studies focused on P. canaliculata, only two specimens with reversed asymmetry have been hitherto reported. Here we report the finding of two live snails and three empty shells of P. canaliculate with anti-clockwise coiling that appeared in two populations from the southern Pampas, Argentina. Both anti-clockwise live snails were males that attempted to copulate with clock-wise females in the laboratory but failed to inseminate them. The apex of anti-clockwise shells and the anatomy of the snails revealed that the reversal of coiling was due to an orthostrophic development of sinistral enantiomorphs. Morphological analysis performed through geometric morphometrics did not find other differences with clock-wise snails other than coiling direction. We conclude that these anti-clockwise snails are probably engendered, as in other snails species, when the mother is a recessive homozygote for reversing alleles that show delayed maternal inheritance. The chances of establishment of populations with dimorphic asymmetry are very low because of the reproductive disadvantages of anti-clockwise individuals.
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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 | 0.000 |
| 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 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".