Atlantic Mangrove Fiddler Crab

Globally, Leptuca thayeri, is distributed in the Western Atlantic around the subtropical mangroves in Ubatuba, State of São Paulo, and Brazil. Within the mangrove trees themselves, Leptuca thayeri is euryhaline and is able to survive in a salinity from 4 to 32. This mangrove fiddler crab is also reliant on the substrate quality, such as: pebble/sand/silt/clay balance, organic matter availability, and the abundance of seagrass. Another factor that the mangrove fiddlers are dependent on in their distribution is temperature. During the warmer months of the year, the population is more pronounced and more widely distributed compared to the colder months of fall and winter.

Living on and within the sediments of mangrove trees, this fiddler crab has an ecological importance. The fiddler crab influences the structure and biology of the sediment through foraging and by constructing burrows for defense. The fiddler crab, Leptuca thayeri, influence bacterial assemblages in the sediment surrounding the mangrove trees they inhabit by decreasing bacterial diversity through foraging. While foraging, these fiddler crabs divide out the individual sediment grains with their spoon-tipped setae. This division of sediment grain allows for the bioturbation of sediments which allows oxygen penetration at depth and remineralization of organic matter.