Graduation Year


Document Type




Degree Granting Department


Major Professor

John M. Lawrence, Ph.D.

Committee Member

Susan S. Bell, Ph.D.

Committee Member

Florence I. Thomas, Ph.D.


encope aberrans, encope michelini, mellita tenuis, organic content, sediment


Sand dollars are abundant and conspicuous macroinvertebrates in sandy habitats in the Gulf of Mexico. They ingest sediment and associated organisms. Given their high abundances, size, and deposit feeding, they likely are the most important consumer coupling primary productivity with the rest of the food chain in these habitats. Moreover, sand dollars bioturbate sediments and affect species diversity and community structure.

Three species of sand dollars in the family Mellitidae,

Mellita tenuis, Encope michelini and Encope aberrans, were studied off the West Coast of Florida. Food and feeding of these sand dollar species were studied to understand their relationship to spatial and temporal patterns.

Particle size and organic content gut contents, collected from inshore and offshore sites, were analyzed and compared with sediment collected concomitantly. Offshore sediment is coarser and has a higher organic content than inshore sediment

. The gut particle sizes are similar for E. michelini and M. tenuis. The gut contents of E. aberrans have larger particles. All three species have gut particles smaller than the ambient sediment. The gut contents and sediment have higher organic content in the fall than the spring. Additionally, the gut organic content varies dielly, with peaks shifting by date. The gut organic content of the three species was higher than the sediment. The gut organic content of E. aberrans was significantly less than that of co-occurring M. tenuis.

The particle sizes and organic content of the gut contents of

Mellita tenuis and Encope michelini are similar. However food type ingested may differ. Encope aberrans may coexist with E. michelini and M. tenuis because it occupies a different niche. Inconsistent peak feeding times could reflect differences in food availability and predation pressure. Inverse relationships between particle size and organic content exist for sediment and gut contents. High densities of M. tenuis inshore may deplete the organic content of the sediment and reverse the negative relationship between particle size and organic content.