Maternal investment and nutrient utilization during early larval development of the sea cucumber Australostichopus mollis
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Echinoderms are widely used to investigate the relationship between egg size, energy content and larval developmental strategies in marine invertebrates; although there have been few studies on ophiuroids and holothuroids. In this paper, we provide the first detailed biochemical information on egg composition and utilization in the planktotrophic holothuroid, Australostichopus mollis. The egg ultrastructure, protein content (85.1 ng egg−1) and lipid:protein ratio of 0.42 were consistent with those of other planktotrophic echinoderms of similar egg size. However, the lipid content (35.6 ng egg−1) was outside the 95% prediction band for the relationship between egg size and lipid content for echinoderms. Triacylglycerol (TAG) was the main energetic lipid present in the egg, with ca 50% of the TAG being utilized to construct the feeding auricularia; the remaining TAG was estimated to be consumed over 114.8 h (4.8 days) of development. Feeding a microalgal diet during early larval development did not affect the rate of TAG utilization, but increased protein content in the 90-h auricularia. Biochemical information from A. mollis eggs/larvae suggests that TAG might be the ancestral maternally derived energetic lipid in the Echinodermata, but also that there may be different patterns of lipid utilization between different classes.
We greatly appreciate the help with sea cucumber collections, lipid/protein analysis and microscopy from Adrian Turner, Erica Zarate, Angela Little and Emily Douglas. We gratefully acknowledge the comments of the three anonymous reviewers, which have greatly improved the manuscript, and the statistical advice of Dr. Katya Ruggiero during the manuscript revision. This research was also supported by a Chilean Government scholarship (Becas-Chile, National Commission for Scientific and Technological Research, CONICYT) awarded to JPD.
Compliance with ethical standards
Conflict of interest
The authors declare they have no conflict of interest.
All applicable guidelines for the care and use of animals were followed.
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