Abstract
For free-spawning marine invertebrates, the egg is the unit of maternal investment in off- spring. For many taxa, there is a major life-history trade-off between production of many small, nutri- ent-poor eggs in high-fecundity species and fewer large, nutrient-rich eggs in low-fecundity species. In echinoderms, the switch from small eggs in species with ancestral-type feeding larvae to large eggs and non-feeding larvae is a significant change with major consequences for larval ecology and juvenile suc- cess. In this first comparative study of maternal investment in the Ophiuroidea across species with a range of egg sizes and larval types, the egg protein and lipid content of 4 species with planktotrophic and 6 species with lecithotrophic larvae were charac- terised. The planktotrophs produced eggs dominated by protein with triacylglycerol as the main energy storage lipid. The switch to lecithotrophy in the Ophiuroidea is associated with an increase in energy storage lipids to produce an energy-dense egg, as is typical of echinoderms with this mode of develop- ment. The eggs of the lecithotrophs, however, con- tained several novel lipid classes not found in ances- tral-type ophiuroid eggs. These eggs also differed from those of other echinoderms with lecithotrophic development in the presence of these novel lipids rather than up-scaling of the ancestral maternal pro- visioning strategy. Our findings support the hypothe- sis of independent evolution of lecithotrophy multi- ple times in the Echinodermata. In the Ophiuroidea, this is seen in the evolution of different lipid pro - visioning patterns between species with large eggs.
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