Maternal effects in a placental live-bearing fish

Maternal effects often provide a mechanism for adaptive transgenerational phenotypic plasticity. The maternal phenotype can profoundly influence the potential for environmentally-induced adjustments of the offspring phenotype, causing correlations between offspring and maternal traits.
We studied the effects of maternal phenotype on offspring phenotype prior to and during the pregnancy in the placental live-bearing fish species Poeciliopsis retropinna collected from the Rio Terraba in Costa Rica. Specifically, we examined how maternal traits such as body fat, lean mass and length influence pre- and post-fertilization maternal provisioning and how this ultimately affects offspring size and body composition at birth.
We found that maternal length proportionally increases egg mass at fertilization and offspring mass at birth, whereas maternal body fat increases offspring mass at birth but does not affect egg mass at fertilization. We furthermore found temporal variation in embryo composition during gestation, with females investing first in embryo somatic lean mass and allocating fat reserves to the embryos only very late in pregnancy. This delay in fat allocation is arguably adaptive, because it postpones an unnecessary high reproductive burden to the mother to late pregnancy. We conclude that offspring provisioning is a plastic phenotypic trait that is strongly determined by maternal phenotype.