Reduced planktotrophy in larvae of <Emphasis Type="Italic">Clypeaster</Emphasis><Emphasis Type="Italic">rosaceus</Emphasis> (Echinodermata,Echiniodea) |
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Authors: | Adam M Reitzel Benjamin G Miner |
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Institution: | (1) Department of Zoology, University of Florida, Gainesville, FL 32611, USA;(2) Department of Biology, Boston University, 5 Cummington ST, Boston, MA 02215, USA;(3) Bodega Marine Laboratory, University of California, Davis, CA 94923, USA;(4) Present address: Department of Biology, Western Washington University, Bellingham, WA 98225, USA |
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Abstract: | Phylogenetic analyses have demonstrated that nonfeeding larvae have evolved from feeding larvae many times among marine invertebrates.
In light of this observation, it is surprising that an intermediate strategy, a larva that can feed but is provisioned with
enough energy to metamorphose without acquiring exogenous food (i.e., facultative planktotrophy), is rare. A hypothesis for
the lack of facultative planktotrophic species among marine invertebrates is that the transition from feeding to nonfeeding
is rapid due to this intermediate stage being evolutionarily unstable. Evidence that would support this hypothesis is if species
with facultative planktotrophy have reduced food assimilation when compared with obligate planktotrophs. We studied a species
with facultative planktotrophic larvae, Clypeaster rosaceus, that is very near the boundary between facultative and obligatory planktotrophy, to answer two questions: (1) does feeding
during the larval stage result in energy gains in larval or juvenile stages and (2) if not, are larvae capable of assimilating
exogenous food at all. Our measurements of energetics in larval and juvenile stages show that C. rosaceus larvae accumulate very little if any energy when fed, but stable isotope data indicate that larvae are able to assimilate
some food. Our results are consistent with similar studies on facultative planktotrophic larvae suggesting poor food assimilation
and rapid loss of larval feeding after a population evolves the ability to reach metamorphosis without feeding (lecithotrophy). |
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