Evolution of gamete attraction molecules: evidence for purifying selection in speract and its receptor, in the pantropical sea urchin <i>Diadema</i>
Bibliographic record
Abstract
Many free-spawning marine invertebrates, such as sea urchins, lack any courtship or assortative mating behavior. Mate recognition in such cases occur at the gametic level, and molecules present on the sperm and egg are major determinants of species-specific fertilization. These molecules must also coevolve in relation to each other in order to preserve functional integrity. When sea urchins release their gametes in seawater, diffusible molecules from the egg, termed sperm-activating peptides, activate and attract the sperm to swim toward the egg, initiating a series of interactions between the gametes. Although the compositions and diversity of such sperm-activating peptides have been characterized in a variety of sea urchins, little is known about the evolution of their genes. Here we characterize the genes encoding the sperm-activating peptide of the egg (speract) and its receptor on the sperm, and examine their evolutionary dynamics in the sea urchin genus Diadema, in the interest of determining whether they are involved in reproductive isolation between the species. We found evidence of purifying selection on several codon sites in both molecules and of selectively neutral evolution in others. The diffusible speract peptide that activates sperm is invariant across species, indicating that Diadema egg peptides do not discriminate between con- and hetero-specific sperm at this stage of the process. Speract and its receptor do not contribute to reproductive isolation in Diadema.
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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 | 0.001 | 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".