Parental care drives the evolution of male reproductive accessory glands across ray-finned fishes
Bibliographic record
Abstract
Reproductive accessory glands are organs involved in reproduction that do not directly produce or release gametes but can play crucial roles in securing reproductive success. In fishes, the 2 leading hypotheses about why accessory glands evolved are (1) in response to sperm competition, or (2) to facilitate parental care activities. Here, we investigate the evolutionary history of accessory glands and test these hypotheses by estimating quantitative differences in evolutionary rates. We found that accessory glands are present in 116 of the 607 sampled species of ray-finned fishes, representing 26/267 families. We estimated that accessory glands have arisen independently ~20 times and that these glands were gained 5.8 times faster in lineages with male parental care, compared to those without male care, supporting the hypothesis that they evolved to facilitate care. In contrast, group spawning, used as a proxy for sperm competition risk, seemed to select against the evolution of accessory glands, as lineages exhibiting group spawning gained accessory glands 3.9 times slower than those with pair spawning (though this failed to reach statistical significance). This study provides new insights into the evolutionary history of accessory glands in fishes and highlights the importance of parental care in shaping reproductive anatomy.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".