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Abstract Maternal effects often provide a mechanism for adaptive transgenerational phenotypic plasticity. The maternal phenotype can profoundly influence the potential for such environmentally induced adjustments of the offspring phenotype, causing correlations between offspring and maternal traits. Here, we study potential effects of the maternal phenotype on offspring provisioning prior to and during gestation in the matrotrophic live‐bearing fish speciesPoeciliopsis retropinna. Specifically, we examine how maternal traits such as body fat, lean mass, and length relate to pre‐ (i.e., allocation to the egg prior to fertilization) and post‐fertilization (i.e., allocation to the embryo during pregnancy) maternal provisioning and how this ultimately affects offspring size and body composition at birth. We show that pre‐ and post‐fertilization maternal provisioning is associated with maternal length and body fat, but not with maternal lean mass. Maternal length is proportionally associated with egg mass at fertilization and offspring mass at birth, notably without changing the ratio of pre‐ to post‐fertilization maternal provisioning. This ratio, referred to as the matrotrophy index (MI), is often used to quantify the level of matrotrophy. By contrast, the proportion of maternal body fat is positively associated with post‐fertilization, but not pre‐fertilization, maternal provisioning and consequently is strongly positively correlated with the MI. We furthermore found that the composition of embryos changes throughout pregnancy. Females invest first in embryo lean mass, and then allocate fat reserves to embryos very late in pregnancy. We argue that this delay in fat allocation may be adaptive, because it delays an unnecessary high reproductive burden to the mother during earlier stages of pregnancy, potentially leading to a more slender body shape and improved locomotor performance. In conclusion, our study suggests that (a) offspring size at birth is a plastic trait that is predicted by both maternal length and body fat, and (b) the MI is a plastic trait that is predicted solely by the proportion of maternal body fat. It herewith provides new insights into the potential maternal causes and consequences of embryo provisioning during pregnancy in matrotrophic live‐bearing species.
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The lifespan of corpora lutea in nonpregnant females is positively correlated with gestation length
Abstract In mammals, a temporary endocrine gland called the corpus luteum forms on the ovary shortly after ovulation and is required for the initiation and maintenance of early pregnancy. However, the corpus luteum persists even when fertilization or pregnancy does not occur, and species-specific variation in the length of this persistence remains enigmatic. Here we perform a comparative evolutionary study across 72 species and show that corpus luteum lifespan in nonpregnant females is positively correlated with gestation length. We argue that the most likely explanation for this correlation is physiological inertia. The corpus luteum begins secreting progesterone prior to implantation, and when pregnancy does not occur it takes time for females to degrade it and prepare the next reproductive cycle. Our study suggests that this physiological inertia is stronger in species with long gestation times.
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- Award ID(s):
- 2027373
- PAR ID:
- 10550080
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Mammalogy
- Volume:
- 106
- Issue:
- 2
- ISSN:
- 0022-2372
- Format(s):
- Medium: X Size: p. 505-511
- Size(s):
- p. 505-511
- Sponsoring Org:
- National Science Foundation
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