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Convergent maternal provisioning and life-history evolution in echinoderms.
Jeffrey T Villinski1, Jennifer C Villinski, Maria Byrne
1jeff@villinski.com
Evolution; International Journal of Organic Evolution
|October 23, 2002
Summary
Marine invertebrates evolve large eggs for nonfeeding development by increasing wax esters, a lipid crucial for buoyancy and provisioning. This adaptation facilitates the frequent transition to lecithotrophic development.
Area of Science:
- Marine biology
- Developmental biology
- Evolutionary biology
Background:
- Lecithotrophic development in marine invertebrates frequently evolves from planktotrophic modes.
- This transition involves the acquisition of large, lipid-rich eggs.
Purpose of the Study:
- Investigate the mechanistic basis of egg-size evolution in lecithotrophy.
- Determine the role of maternally provisioned lipids, specifically wax esters, in this developmental shift.
Main Methods:
- Lipid identification and quantification in eggs of sea urchins and sea stars.
- Comparative analysis using independent contrasts to account for phylogeny.
- Experimental manipulation of wax ester levels in Heliocidaris erythrogramma embryos.
Main Results:
- Lecithotrophic species have large eggs dominated by wax esters, unlike planktotrophic species with triglyceride-rich small eggs.
- Egg enlargement in lecithotrophs is strongly correlated with increased wax ester deposition.
- Reducing wax esters in H. erythrogramma embryos yielded nonbuoyant larvae, indicating a role in buoyancy.
Conclusions:
- Wax esters are a key component in the evolution of large, buoyant eggs for lecithotrophic development.
- The modification of preexisting oogenic processes, like wax ester production, facilitates frequent larval mode evolution in marine invertebrates.