Convergent Evolutionary Dead‐End and Breakdown of Hard Chorion in Parental‐Egg‐Care Fish Reproductive Strategies
Bibliographic record
Abstract
Fish exhibit a diverse array of reproductive strategies adapted to various ecological niches. Parental egg-care, including live-bearing, mouth-brooding, and male egg protection by brood pouches, represents an effective strategy for ensuring larval survival and has emerged independently in multiple lineages. Despite the recognised evolutionary bias that favours a strategy transition from non-carer to egg-carer, the genetic mechanisms underlying this bias and the commonalities among parental egg-care species remain elusive. This study explores the relationship between egg-care and the chorion hardening system crucial for protecting eggs in non-care species. By analysing whole genome sequences of 240 species of Acanthopterygii across 25 orders, we discovered that multiple genes associated with chorion hardening have become pseudogenes in various egg-care species, indicating a collapse of the chorion hardening system in these fish. These findings suggest that the evolutionary bias in fish reproductive strategies not only aims to enhance survival efficiency but also imposes a constraint on egg-care species, preventing them from reverting to a reproductive strategy relying on a hardened chorion. In particular, alveolin, previously characterised as a single mutant resulting in significantly fragile chorion in medaka, suggests a strong correlation between egg-care strategy and gene loss. Our results suggest an evolutionary dead-end because gene loss may impose an evolutionary constraint at the behavioural level. The observed association between gene loss and reproductive strategies provides insights into suitable reproductive environments for each species and may facilitate non-invasive estimation of reproductive strategies in species with unknown breeding strategies.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".