Female Sailfin Mollies are able to modify their form of reproduction from a more matrotrophic to a more lecithotrophic provision of nutrients after assessing the condition of their environment (Trexler, 1997). Sailfin Mollies that are pregnant in the spring have high food availability making matrotrophy advantageous (Trexler, 1997). Conversely, Sailfin Mollies pregnant in the summer have lower food availability and find lecithotrophy to be more advantageous (Trexler, 1997). The mode of reproduction utilized by Sailfin Mollies is also influenced by the size of the female. Smaller females tended to reproduce fewer lecithotrophic eggs, while larger females produced larger broods nourished matrotrophically (Trexler, 1997). It is likely that the lipid reserves of small females are so small that even the slightest fluctuations in environment would result in their lipid reserve falling to critical levels and necessitating embryo abortion (Reznick et. al., 2007).
The Sailfin Mollies plasticity in the mode of reproduction can be observed by measuring the percent change in dry mass between eggs and full term embryos collected from the same mother (Lombardi, 1996). A large increase in the embryos weight indicates matrotrophic reproduction. The greater the increase in embryonic dry weight, the more "advanced" the form of matrotrophy utilized by the mother (Lombardi, 1996).
For example: tiger shark embryos are oophageous and have a dry mass increase of 840%-1050%, while butterfly rays are nourished by placental analogues and have a dry mass increase of 1690%-4900% (Lombardi, 1996). These make sense as oophagy is considered to be the least derived form of matrotrophy (Wourms, 1993).
Sailfin Mollie from
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