Corrington (1927) defined L. dubia as a scavenger, feeding on easily procured plant and animal tissue and detritus. In seagrass beds, the spider crab consumes macroalgae as a portion of its diet, including Gracilaria tikvahiae and other algae of the genera Ulva, Hypnea, Chondria and Padina (Stachowicz & Hay 1999). When in association with various species of medusae, L. dubia has been found to feed on the mesoglea, the transparent body tissue of the jelly (Jachowski 1963, Phillips et al. 1969, Tunberg & Reed 2004). Predators: As juveniles, spider crabs are commonly preyed upon by larger fishes including: adult pinfish, Lagodon rhomboides; juvenile gag grouper, Mycteroperca microlepis; and oyster toadfish, Opsanus tau (Stachowicz & Hay 1999). To avoid predation, L. dubia decorates its shell with unpalatable algal and invertebrate species, including the brown alga, Dictyota menstrualis (Stachowicz & Hay 1999), and the sun sponge, Hymeniacidon heliophila (Stachowicz & Hay 2000). As the crab grows larger than the mouth gape of its fish predators, its predation risk lowers and it ceases this decorative behavior (Stachowicz & Hay 1999). Parasites: Several marine species can become infected with parasites in the form of worms, copepods, barnacles and other organisms. One such relationship has been documented between L. dubia and the marine fungus, Lagenidium callinectes (Bland & Amerson 1974). The fungus infects eggs of L. dubia; the Atlantic mud crab, Panopeus herbstii; and the blue crab, Callinectes sapidus (Bland & Amerson 1974), as well as other commonly aquacultured species (eg. Ramasamy et al. 2006).
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