Hormones reflect the impacts of reproductive rest on subsequent pregnancy in a marine predator
Bibliographic record
Abstract
Abstract After reaching sexual maturity, iteroparous female vertebrates may intermittently skip producing offspring, effectively taking a year of reproductive rest. This may confer benefits to lifetime fitness by enhancing future reproductive success. To identify links between reproductive rest and subsequent reproductive outcomes, the physiological status of female Weddell seals ( Leptonychotes weddellii ) that skipped pupping in the current year (skip females, n = 45) and seals that gave birth (postpartum females, n = 87) was compared. Serum concentrations of hormones (progesterone, oestrogen, luteinizing hormone, follicle‐stimulating hormone, prolactin, thyroxine [T 4 ] and cortisol) were measured during the pupping period, breeding period and early gestation. Transrectal ultrasonography was used to image ovaries and detect early pregnancies. Range‐wide censuses conducted the next year determined if females successfully gave birth. Skip females ovulated up to 4 weeks earlier than postpartum seals and gave birth earlier the following year. Postpartum seals that gave birth late in the pupping season ovulated at fewer days postpartum than seals that gave birth early and had the lowest rates of pregnancy and successful birth. Late‐birthing females were therefore most likely to skip reproduction the following year, likely shifting subsequent reproductive timing forward. Skip females had higher serum concentrations of T 4 , oestrogen and progesterone than postpartum females in both breeding and early gestation periods, plus lower serum cortisol concentrations during early gestation. Serum T 4 concentrations were positively correlated with higher likelihoods that seals were pregnant and would successfully give birth. Postpartum females had higher serum prolactin concentrations than skip females in the pupping and breeding periods. However, prolactin declined across the summer in all animals, likely reflecting a seasonal transition from a breeding to a non‐breeding physiological state. This study revealed that physiological differences between skip and postpartum female Weddell seals persisted long after pupping and into the next reproductive cycle. Findings on trade‐offs between current and future reproduction in a polar pinniped suggest that reproductive rest allows birth timing to advance the next season, helping improve reproductive fitness and maintaining a tight temporal window for birth in the Antarctic marine environment. Read the free Plain Language Summary for this article on the Journal blog.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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".