Date of Award

Spring 5-21-2018

Document Type

Undergraduate Honors Thesis

Degree Name

Bachelor of Arts in Marine Science

Department

Environmental and Ocean Sciences

Advisor

Nathalie Reyns

Abstract

Three species of fiddler crabs, Uca minax, U. pugnax, and U. pugilator, are commonly found in estuaries along the Atlantic coast, each with distinct adult habitats differing in salinity and sediment grain size. Prior research has found evidence for larvae exhibiting selective settlement; however, the degree to which and the method by which they choose their species-appropriate habitat to settle in is still unknown. Additionally, a recent study determined that chemical cues from adult crabs stimulate molting in field-caught fiddler crab megalopae, as previously determined in lab-reared megalopae; however, in 35 ppt seawater, few U. minax molted. This study tested the hypotheses that 1) chemical cues from adult fiddler crabs would stimulate molting of conspecific megalopae in 10 ppt seawater, and 2) that at 10 ppt, more U. minax would molt than at 35 ppt. Adult chemical cues accelerated molting in field-caught megalopae of U. pugilator and U. pugnax, which both molted significantly earlier in all odor water treatments than in the control water, and fastest in conspecific water. U. pugilator megalopae were stimulated to molt in all treatments, whereas U. pugnax molted mostly in conspecific odor. However, even at 10 ppt, few U. minax molted and there were no differences in molting frequency or time among treatments. The few U. minax molts suggest that these experimental conditions may still not be ideal, and other factors may be responsible for stimulating and accelerating their molting and settlement site selection.

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