Date of Award

8-2015

Rights

© 2015 Bryan Tate

Document Type

Thesis

Degree Name

Master of Science in Biological Sciences

Department

Biological Science

First Advisor

Jeri Fox

Second Advisor

Stine Brown

Third Advisor

Stephan Zeeman

Fourth Advisor

Anna Bass

Abstract

During early life stages, nutrients are crucial to the proper development of larval marine invertebrates. Many such larvae are lecithotrophic and therefore do not actively feed; however, a large body of research has shown that lecithotrophic larvae take in dissolved organic material (DOM) including amino acids and sugars, contributing heavily to metabolic requirements. Another dissolved nutrient, iodine, is useful to marine invertebrates for the production of organic compounds. Some of these compounds (thyroid hormones, THs) are historically thought to be used almost exclusively by vertebrates, though studies have shown that THs are also useful to some marine invertebrates for developmental and homeostatic processes. Aeolidiella stephanieae is an aeolid nudibranch found exclusively in the Florida Keys. The purpose of this study was to determine whether dissolved nutrients are beneficial to A. stephanieae veligers during development. The effects of a thyroid hormone (triiodothyronine), a sugar (glucose), an amino acid (alanine), and a form of iodine (iodide) added to rearing water prior to metamorphosis were investigated. Survival and successful metamorphosis of A. stephanieae individuals at 15 days after oviposition were observed for each treatment. A. stephanieae veliger survival and successful metamorphosis were not negatively impacted by the addition of triiodothyronine, glucose, or iodide. Survival and successful metamorphosis, as well as the presence of veligers at the 15-day mark were all negatively affected by the presence of alanine. Alanine concentrations had the most marked effect on survival, showing declines in survival proportionate to alanine concentration. Significant declines in survival were present even at the lowest alanine concentration. The rapid reproduction of heterotrophic bacteria in response to the abundance of free amino acids is the most likely culprit for mortality seen with alanine supplementation. It is unlikely that triiodothyronine, glucose, alanine, or iodide alone are beneficial to A. stephanieae veligers; however, it is still possible that these nutrients or a combination thereof at optimal concentrations may positively affect body mass and soft tissue growth. Future research involving lecithotrophic larvae paired with these and other nutrients would benefit from using species with larger eggs and larval stages for the purpose of protein and body mass analysis. In turn, this research could foster a better understanding of the importance of dissolved nutrients to lecithotrophic invertebrate larvae.

Comments

Master's thesis

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