Do placental species abort offspring? Testing an assumption of the Trexler–DeAngelis model

Abstract

Summary 1.We investigate how resource level affects reproduction in matrotrophic ( Poeciliopsis prolifica ) and lecithotrophic ( P. monacha ) fishes. 2. One of our goals was to test an assumption of the Trexler-DeAngelis model for the evolution of matrotrophy, which was that matrotrophic species can adjust litter size by aborting offspring in low food conditions. Our more general goal was to elucidate other differences between the reproductive modes. 3. Both species have superfetation and c. 30-day development time. Females of each species were assigned to high or low food availability for 30 days, or one gestation period. Any young born during that time interval would have initiated development before the initiation of the experiment. If embryos are aborted, then this would be seen as a reduction in brood size in the low food treatment relative to the high food treatment within this period. 4. Our results suggest P. monacha responds to low food by sacrificing reproduction to maintain lipids, while P. prolifica maintains reproduction at the expense of lipids. Neither species showed a significant reduction in offspring number over the course of the experiment, suggesting that these species do not abort offspring in low food conditions.

High Food Abundance Permits the Evolution of Placentotrophy: Evidence from a Placental Lizard,Pseudemoia entrecasteauxii

“…In matrotrophic fish, food limitation during gestation causes reductions in matrotrophic provisioning to offspring (Marsh-Matthews and Deaton 2006;Banet et al 2010;Pollux and Reznick 2011). Unlike P. entrecasteauxii, matrotrophic fish usually do not abort or cannibalize offspring when food availability is limited during gestation (Banet and Reznick 2008;Banet et al 2010;Pollux and Reznick 2011; but see Riesch et al 2013). Two key differences may explain why a placentotrophic reptile is more likely to abort offspring than matrotrophic fish.…”

“…When food is limiting, females provide less energy, protein, and lipid to offspring, which should allow them to better maintain their own energy, protein, and lipid reserves. Undeveloped eggs and unborn offspring do not increase in mass relative to freshly ovulated eggs, so abortion likely allows females to save nutrients that would otherwise have been allocated to production of small, potentially poor-quality offspring (reviewed by Sinervo 1990;Banet and Reznick 2008). Furthermore, each offspring or egg contains nearly 10% of an adult female's energy content, approximately 7% of a female's protein content, and 10-20% of a female's lipid content, so cannibalism allows females to recoup substantial quantities of nutrients quickly after reproduction.…”

“…Two key differences may explain why a placentotrophic reptile is more likely to abort offspring than matrotrophic fish. First, the offspring of matrotrophic fish are very small; Poeciliopsis prolifica offspring mass averages less than 0.2% of maternal mass (Banet and Reznick 2008). In P. entrecasteauxii, offspring dry mass ranges from 5.8% to 6.1% of maternal dry mass, depending on food abundance.…”

“…The Trexler and DeAngelis (2003) model has been tested several times in fish, in which food limitation during gestation causes reductions in matrotrophic provisioning, offspring size, and maternal mass in matrotrophic species but affects only maternal mass in lecithotrophic species (Marsh-Matthews and Deaton 2006;Banet et al 2010;Pollux and Reznick 2011;Riesch et al 2013). Food restriction rarely causes abortion or cannibalism of offspring in either matrotrophic or lecithotrophic fish (Banet and Reznick 2008;Banet et al 2010;Pollux and Reznick 2011; but see Riesch et al 2013). In lecithotrophic reptiles, food limitation during gestation does not affect offspring size or developmental success (Gregory and Skebo 1998; reviewed by Lourdais et al 2002;Hare and Cree 2010), likely because placental nutrient transport is minimal in these taxa and embryos rely almost entirely on yolk for nutrition .…”

A Novel Pattern of Placental Leucine Transfer During Mid to Late Gestation in a Highly Placentotrophic Viviparous Lizard

“…Therefore, the source of fatty acids transferred across the placenta during gestation is likely to be these maternal energy reserves. In contrast, the source of other nutrients such as amino acids is more likely to be food consumed by the female during gestation (i.e., income provisioning), especially in highly placentotrophic species (Shine and Downes, ; Thompson et al, ; also see Santos et al, ; Banet and Reznick, ; Warner et al, ; Itonaga et al, ). For amino acids, therefore, food availability and maternal feeding rates during gestation may affect the magnitude of placental support related to embryonic stage.…”