Limulus polyphemus

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Limulus polyphemus-Horseshoe Crab

Range - The horseshoe crab is a benthic creature. The horseshoe crab ranges from the Yucatan peninsula to northern Maine, and are most abundant between Virginia and New Jersey.

Description- The body of a horseshoe crab is divided into three parts: the prosoma, opisthosoma and telson. The average size is about 13-16 inches long. Seven pairs of leg-like appendages are found on the underside of the shell. These legs are used for eating and locomotion. Like many animals with hard shells, a horseshoe crab must molt or shed its shell as it grows.

Life History- The horseshoe crab starts out as and egg. It takes about two weeks for the eggs to hatch; this usually happens during the spring tides. During the two week thought the horseshoe crab undergoes four molts within the egg. Upon hatching, the trilobite larvae dig their way out of the sand. They are approximately 3 mm across and look just like miniature adults. Around day 21 the larvae shed their shell and become juveniles that are about a quarter of an inch wide. Horseshoe crabs initially molt an average of three or four times a year. Males are sexually mature at their sixteenth molt, about eight years old. Females need at least seventeen molts, so about ten years old they are sexually mature.

Ecological Notes- Can be found around shallow ocean waters living in sandy or muddy substrates.

Personal Information- During summer nights these crabs come out in great numbers to feed. During the winter they stay in their burrows and hibernate. The main habitat of these crabs, sandy beaches, are heavily impacted by human and vehicle trampling. This compression of the sand leads to direct crushing or the crabs, and reduces habitat suitability, reduction of food supply, interference with mating rituals. While they are not currently listed as endangered or threatened, these crabs are usually more frequent on beaches less visited by people.

Journal Articles- For more information check out these articles

Measures turning tide in horseshoe crabs’ favor By Kathy Reshetiloff / Bay Naturalist

The ancient origin of the complement system By Yong Zhu1, Saravanan Thangamani1, Bow Ho2 and Jeak Ling Ding1 Department of Biological Science, National University of Singapore, Singapore, Singapore Department of Microbiology, National University of Singapore, Singapore, Singapore

References: (n.d.). Retrieved from

History and biology.(n.d.). Retrieved from

By Katelyn Stewart (2012)