Coenobita compressus is a terrestrial hermit crab of the genus Coenobita which is a genus that has been widely studied and is comprised of approximately a dozen species worldwide (Laidre 2012). It is commonly known as the Ecuador Hermit Crab or the Pacific Hermit Crab. C. compressus like all hermit crabs has an asymmetrical body morphology and soft abdomen. Its abdomen is displaced to its right to fit dextrally coiled shells (Herreid and Full 1985). C. compressus varies widely in terms of coloration with younger animals tending to have uniform coloration ranging from blue-green to gray-brown, while larger animals have more contrast with pale grey, black, and brown coloration (Ball 1972). The Coenobita genus hermit crabs brood eggs on the abdomen and then release them as larva into out flowing rivers or streams into the ocean (Laidre 2012). These larvae then drift until they sink and find a suitable gastropod shell to use as a home (Laidre 2012). They will change this shell throughout their lifetime. They walk benthically with this home at first but eventually emerge onto land (Laidre 2012). They then spend the rest of their lives foraging on the beach and remaining primarily on soil (Laidre 2012). The most common home choice that has been noted in the field as being the preference of C. compressus to inhabit is the shell of the gastropodNerita scabricosta. Males have been noted as being larger than females (Ball 1972). C. compressus is distributed widely on the Pacific Coast from lower California to Mexico (Ball 1972, Bright 1966, Burggen and McMahon 1988, Laidre 2012). They can be found up to 1 km inland but are typically found within 100 m of the shore (Burggen and McMahon 1988). They have been documented as living in rocks and grass above high tide in the tropics (Herreid and Full 1985), under ledges, in small rocky caves, and under logs and driftwood (Ball 1972) but are commonly found on or near sand or gravel beaches (Abrams 1978). C. compressus is a general scavenger and eats a wide range of organic matter (Abrams 1978) including fragmented wood, feces, . They have also been cited as being agricultural pests and eating crops such as cacao, plátano, and rice (Ball 1972, Burggen and McMahon 1988). Research has also suggested that their feeding behaviors depend largely on environmental conditions (Ball 1972) and that they use social facilitation as a foraging strategy (Kurta 1982). They are nocturnal (Ball 1972) but can also be very active during the early morning hours (Kurta 1982). C. compressus walk forward on six legs using an alternating tripod gait similar to that of insects (Herreid and Full 1985). They also have longer left appendages which they extend further laterally from the midline during their stride to compensate for their asymmetry (Herreid and Full 1985). The abdomen is normally carried off the ground but dragged when the shell is large (Herreid and Full 1985). Research has also indicated that niche-construction drives social dependence, such that individuals can only survive in remodeled shells handed down from conspecifics (Laidre 2012).
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