Evolution of Developmental Pattern and Larval Form in the Ophiuroids of Oregon and Beyond
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Date
2024-03-25
Authors
Nakata, Nicole
Journal Title
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Publisher
University of Oregon
Abstract
Despite the ubiquity and known impacts of transitions in developmental pattern in marine invertebrates, many taxa have been insufficiently analyzed. In Chapter II, I report the effects of larval feeding in an undescribed facultative planktotroph, Amphiodia sp. opaque. By culturing larvae with and without food and observing development, I found that larval feeding led to faster development times, greater percent metamorphosis, and larger juveniles able to evade starvation longer than individuals that did not receive food. We compared metrics of early life stages using a series of generalized linear models, and model fitting was determined using Akaike’s Information Criterion (AIC). Scores for each model and test are included as supplementary tables.
In Chapter III, I present a summary of developmental diversity in the ophiuroids of the northeast Pacific Ocean. We used DNA barcoding to identify eighteen species from the plankton of the southern Oregon coast. We found four species with reduced plutei, one with vitellaria, three with pelagic direct development, and ten with planktotrophic ophioplutei (including one followed by a vitellaria).
This diversity of larval forms suggests multiple transitions from feeding to nonfeeding larvae in the Amphiuridae, which I tested for in Chapter IV using comparative phylogenetic analyses. To do so, I constructed a four-gene phylogenetic hypothesis for species with known development pattern in the family Amphiuridae. Single-gene trees were made to check for congruence between loci and the multi-gene dataset and are included as supplementary figures. This analysis inferred a brooding ancestor, an instance of re-acquisition of feeding, and multiple transitions back to nonfeeding larvae. The analysis inferred multiple transitions from brooding to nonfeeding planktonic development via pelagic direct development.
Altogether, this work introduces new examples of the developmental patterns in Ophiuroidea, including an example of facultative planktotrophy, a rare developmental pattern that may represent an evolutionary intermediate between feeding and nonfeeding larvae. We show the effectiveness of DNA barcoding for identifying the early life stages of benthic marine invertebrates. Finally, I found that reconstructed ancestral states of developmental pattern are influenced by tree topology and completeness of the dataset.
This dissertation includes previously published and unpublished co-authored material.
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Keywords
evolutionary transitions, larvae, marine invertebrates, ophiopluteus, Ophiuroidea, vitellaria