Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
Organisms have limited resources available to invest in reproduction, causing a tradeoff between the number and size of offspring. One consequence of this tradeoff has been the evolution of disparate developmental modes, even among close relatives. Marine invertebrates are well known for their tremendous diversity of developmental patterns, much of which has been attributed to changes in maternal investment. In particular, echinoid echinoderms have been widely used to experimentally manipulate how changes in maternal investment affect development. Here I test the generality of the echinoid results by experimentally reducing maternal investment in the seastars Pisaster ochraceus and Asterias forbesi. Maternal investment in embryos was halved at the two-cell stage by killing one blastomere with a laser. Larvae from manipulated embryos were compared to unmanipulated sibling embryos to test for effects of reduced maternal investment on larval development and juvenile quality. In one experiment I also varied larval food supply during development of A. forbesi. My response variables were time to metamorphosis, spine number, disk diameter, and disk area at metamorphosis. In P. ochraceus there were no significant differences between juveniles from manipulated and unmanipulated embryos. In A. forbesi, for all response variables, reductions in larval food had a significant and much larger effect than reductions in maternal investment. Reductions in maternal investment significantly reduced disk diameter but had no affect on other metrics. These results indicate that seastar larvae may be capable of compensatory growth in response to reduced maternal investment and that food levels are more important than maternal investment in determining larval and juvenile quality.
Trackenberg, Stacy Nicole, "Effects of Changes in Egg Size and Larval Food Supply on the Development of Two Species of Seastars" (2016). Undergraduate Honors Theses. William & Mary. Paper 920.
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