Body Size of the Endosymbiotic Pea Crab Tumidotheres maculatus: Larger Hosts Hold Larger Crabs

The endosymbiotic pea crab, Tumidotheres maculatus, uses a broad range of host taxa, including several bivalve species, in the northern Gulf of Mexico. Because shelter size affects the size of other, free-living crab species, we hypothesized that pea crabs living in larger bivalve hosts should attain larger sizes. Crabs and hosts collected from 3 field sites in northern Florida show this trend. We examined crabs living in a large host, the pen shell Atrina rigida, and found them to be larger than pea crabs living in a small host, the bay scallop Argopecten irradians. Moreover, this trend was only apparent among female pea crabs, which are lifelong endosymbionts, but not among males, which are free-ranging and move among hosts. Our data support the broader conclusion that shelter size influences adult crab size in brachyuran crabs