Reduced fecundity in non‐parasitic lampreys may not be due to heterochronic shift in ovarian differentiation
Bibliographic record
Abstract
Abstract Heterochrony is an important mechanism for the evolution of differences between and within species. In lampreys, heterochrony has been suggested as a mechanism contributing to fecundity differences in non‐parasitic versus parasitic species. Non‐parasitic lampreys, which do not feed at all after metamorphosis, have much smaller body sizes at maturation and therefore much lower fecundity than parasitic lampreys. Previous studies have suggested that this fecundity difference is established in the larval stage through ovarian differentiation at a younger age (and therefore smaller body size) in non‐parasitic females, leading to production of fewer oocytes. The current study examined whether this pattern is applicable in two additional lamprey species. The timing of histological ovarian differentiation was determined in larval parasitic chestnut lamprey Ichthyomyzon castaneus and non‐parasitic northern brook lamprey I. fossor in southeastern Manitoba, Canada, and potential fecundity was compared through oocyte counts in differentiated females of both species. Ovarian differentiation occurred in age classes 1 and 2 in both chestnut and northern brook lampreys, and there were no significant differences in the timing of ovarian differentiation between species; this indicates that the timing of ovarian differentiation is not a reliable marker of life history type. Factors such as growth and body condition may determine whether an individual undergoes ovarian differentiation in age class 1 or 2. Chestnut and northern brook lampreys had similar minimum oocyte counts; however, the average and maximum oocyte counts were higher in chestnut lamprey in each age class. As the timing of ovarian differentiation is similar in chestnut and northern brook lampreys, the higher potential fecundity of chestnut lamprey must originate through mechanisms other than heterochrony.
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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) | 0.001 | 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".