Term of Award

Spring 2003

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Sophie B. George

Committee Member 1

Stephen P. Vives

Committee Member 2

Alan Harvey

Abstract

Larval growth and development of two sand dollars, Mellita isometra and Dendraster excentricus was investigated by assigning larvae to several single and mixed algal diets, three levels of salinity and salinity-diet combinations in the laboratory. For M. isometra, Chaetoceros muelleri, Isochtysis galbana and Dunaliella tertiolectu were used as single algal diets and /. galbana -D. tertiolecta, I. galbana-C. muelleri and C. muelleri - D. tertiolecta as a mixed algal diets. Among the single algal diets, larvae fed Isochrysis galbana were the smallest. They developed smaller rudiments and had the lowest protein content. Mellita larvae fed C. muelleri or the mixed algal diet of /. galbana and D. tertiolecta developed the fastest, had the biggest rudiments, and had the highest protein content. Low salinities favored faster rudiment development. The biggest rudiments were produced by Mellita larvae at 27%o. Mellita larvae maintained at 32%o and fed C. muelleri were significantly longer, wider and had longer posterodorsal arms than larvae in the other two treatments. Dendraster excentricus larvae were fed two single diets: - Dunaliella tertiolecta and Rhodomonas sp. and three mixed diets-D. tertiolecta and Isochrysis galhana, Rhodomonas sp. and /. galbana, and D. tertiolecta and Rhodomonas sp. were used. Rhodomonas sp. had the highest percentage of the long chain PUFAs (polyunsaturated fatty acids), D. tertiolecta had the highest percentage of MUFAs (monounsaturated fatty acids) and I. galbana had the highest percentage of SAFAs (saturated fatty acids). Early larval stages ingested a higher volume of the small alga /. galbana and later larval stages ingested a higher volume of the bigger cells D. tertiolecta and Rhodomonas sp. Larvae fed I. galbana and D. tertiolecta developed faster, had bigger rudiments, the highest protein content and produced more juveniles than the other four diet treatments. Larvae were able to assimilate SAFAs and MUFAs from the algae and synthesize long chain PUFAs.

In conclusion, a single algal diet consisting of C. muelleri was just as effective as a mixed algal diet of /, galbana and D. tertiolecta for optimal larval growth and development of the sand dollar M. isometra. I. galbana was ineffective regardless of salinity. Similar to M. isometra, for D. excentricus a mixed algal diet of I.galbana- D. tertiolecta was the best in terms of larval growth and rudiment development.

Copyright

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