Adult Uca spp. (fiddler crab) Chemical Cue Presence and Effect on Molting Rate of Uca spp. Megalopae into Juveniles

Past research has shown that adult conspecific chemical cues of brachyuran crabs stimulate molting in their megalopae. This study hypothesized that adult fiddler crab (genus Uca) chemical cues would stimulate metamorphosis in their conspecific megalopae, which would demonstrate that adult conspecifics indicate proper settlement sites for their megalopae. Field-caught megalopae were placed in individual vials of seawater, U. minax water, U. pugilator water, or U. pugnax water and the time each took to metamorphose was recorded. Both U. pugilator and U. pugnax megalopae did not molt equally across the four different water treatments (U. pugilator: χ²₃=16.87, p<0.005; U. pugnax: χ²₃=31.16, p<<0.001). They favored molting in their conspecific odor water, as did U. minax. No statistical tests were run for U. minax due to the small sample size. The average molt time for each of the three species was not the shortest in their respective conspecific odor water; however, U. pugilator did molt faster in Uca water than seawater (t₁₄₉=6.22; p=0.0137). This study concluded that when using field-caught megalopae, it is more important to observe which water treatment stimulated the most molts for each Uca spp. rather than the amount of time each took to molt; therefore, it was observed that U. pugilator, U. pugnax, and U. minax have the highest molting response in either conspecific or Uca scented water, revealing that adult Uca chemical cue presence signals ideal settlement sites for the megalopae to join their adult conspecifics and molt into juveniles.