Background Information

Background Information

 

Uca minax is a fiddler crab species commonly found along the United States' East Coast. All fiddler male fiddler crabs, regardless of the species, have a major claw, a claw that is significantly bigger than their other claw. This can be on either side, allowing a male fiddler crab to be characterized by either being left- or right-clawed. The minax species have horizontal indentations behind their compounded eyes, meaning their eyes are atop a stalk. Continuing, this species of fiddler crabs is brown and gray with red joints that connect the claws to the carapace and has eight walking legs that vary between being a light brown or dark green (Bethany Fisher).

Fiddler crabs live in coastal wetlands in the intertidal regions of the coast, meaning seawater from the ocean periodically floods their habitat based on the high and low tides. Coastal wetlands are divided into the following three subsections: the high marsh, midshore, and low marsh. The high marsh is only fully submerged during high spring tides, a high tide directly after a full or new moon. Many different types of plants grow here, including cordgrass, reeds, and glassworts. Runoff bring most of the salt from the high marsh into the midshore, the saltiest portion of coastal wetlands that inhabits different species of succulents (Susan Woodward). The low marsh is the least salty of the three portions; this is due to the fact that is most always submerged by water, lessening the amount of evaporation occurring. The Uca minax mostly inhabit this region of the wetlands due to its low salinity. The lack of oxygen is also due to the increased amount of time this area spends underwater. Many plants in the low marsh have adapted short roots that take oxygen gas from the air and transport it to their deeper roots using aerenchyma specialized tissue (Susan Woodward). Continuing, very little organisms in the coastal wetlands actually feed on the plant life, thus creating massive amounts of decaying plants that take up lots of the available oxygen. This causes hypoxia, or lack of oxygen, for many of the other organisms that call this area home, a scientific phenomena responsible for the rotten egg smell most often associated with coastal wetlands (Susan Woodward).

However, fiddler crabs burrow into the sediment and use them for protection against predators and to reside in during high tides, as well as to mate in. These burrows aerate the soil and move the sediment and nutrients around, thus maximizing their availability for other organisms to use and increasing soil water content and Carbon and Nitrogen turnover rates (Subhasish Chatterjee). Fiddler crab burrows also accelerate the environmental processes that take place in the habitat to make it viable for life. On another note, when fiddler crabs feed, they use the first and second maxillipeds, which separate the sediment from the detritus and organic matter. This creates the sand pellets commonly associated with the beach (Subhasish Chatterjee). 

A photo taken by B. Astorino of the coastal
wetlands at Spermaceti Cove.

A male Uca minax fiddler crab displays his major claw
(Michael Rosenberg).

The nature of this project is to conduct a population analysis of the fiddler crabs on Sandy Hook, New Jersey, specifically at Spermaceti Cove. The end goal is to determine how the population is compared to previous years' data collection points. By continuing this project for years to come, the population analysis will continue to increase in accuracy, as there will be more data to base hypotheses and conclude how the species is doing. Ultimately, this project is useful to quantify whether or not the fiddler crabs are thriving, and to potentially determine the variables that are affecting the population. 

A photo, taken by B. Astorino, of Spermaceti Cove, where all of
the data points are being collected.

It is important that population analyses be conducted during the breeding season of the species being studied in order to get a more accurate count of the population. When it is not the breeding season, the population steadily decreases as little to no offspring are being produced. Continuing, fiddler crabs remain underground in their burrows throughout the winter months. With this being said, the height of the population during the year occurs during breeding season, giving ample data points for research. Fiddler crabs breed every two weeks in the summer months. As a result, the fiddler crabs at Spermaceti Cove on Sandy Hook, New Jersey have been counted every two weeks since the beginning of June, and will continue to be counting until none are spotted.

Many red-jointed fiddler crabs are feeding among the
reeds and glassworts of the coastal wetlands
(Harry Lee).

Works Cited

Chatterjee, Subhasish. "Ecological Role of Fiddler Crabs." Marine Biological Association of India (2014). Web. 

Fisher, Bethany. "Red Jointed Fiddler." Animal Diversity Web. University of Michigan, 2017. Web. 

Lee, Harry. "Red Jointed Fiddler Crabs at Vilano Beach." Jax Shells. Jax Shells, 2017. Web. 

Rosenberg, Michael, Dr. "Uca Minax." Uca Minax. PLoS ONE, 2017. Web. 

Woodward, Susan. "Salt Marshes." Biomes of the World. Radford University, 2017. Web.