Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
Jonathan D. Allen
Margaret Somosi Saha
S. Laurie Sanderson
Deborah K. Steinberg
Broadcast spawning is a common reproductive strategy in marine environments. While there are many advantages to this mode of reproduction, it has the drawback of leaving offspring exposed to environmental fluctuations. To study the effects of temperature and salinity fluctuations on development, I fertilized eggs of three different echinoid echinoderm species (Strongylocentrotus droebachiensis, Echinarachinus parma, and Lytechinus variegatus) under a range of conditions. In all three species, a novel response of embryonic twinning was seen under at least one combination of environmental conditions. Twinning percentages were variable among the three species with E. parma having the highest frequency. Significant variation in twinning frequency was also observed within species. In the most extreme cases up to 28% of embryos in a single treatment were observed to twin. To see how twinning affected development, we followed replicate pairs of E. parma larvae that were derived from twinning events. Twins were measured and compared to untwinned siblings. Overall, twins grew at a slower rate than untwinned siblings. In addition to reduced growth rates, twins were also delayed in reaching subsequent developmental stages. Other novel developmental abnormalities were observed in this study. Delay of hatching was seen frequently in E. parma embryos that had been exposed to reduced salinity and increased temperature. Prior to my study, environmentally cued hatching had been described in every deuterostome phyla except for echinoderms. The observation that it also occurs in echinoderms was an unexpected outcome. Normal hatching occurs at the blastula stage in echinoderms, but some embryos delayed hatching until shortly after gastrulation while others were four-arm larvae before hatching. The production of multiples and delays in hatching are both previously undocumented responses to environmental stress and their consequences for coastal populations should be explored further. Understanding how embryos and larvae respond to changes in temperature and salinity can help explain how these species persist in variable habitats and also how they may respond to future effects of climate change.
Armstrong, Anne Frances, "The Effects of Temperature and Salinity Fluctuation on the Early Life History Stages of Echinoid Echinoderms" (2011). Undergraduate Honors Theses. William & Mary. Paper 373.
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