P1.181 Wednesday, Jan. 4 Undersea Orientation Mechanisms of Horseshoe Crabs ERNST, D.A.*; LOHMANN, K.J.; University of North Carolina at Chapel Hill; University of North Carolina at Chapel Hill email@example.com
During the high tides of spring, the American horseshoe crab (Limulus polyphemus) can be found in large mating aggregations along low-energy sandy beaches ranging from the east coast of Maine to the Yucatan Peninsula. Little is known, however, about the sensory cues and navigational strategies used by horseshoe crabs to locate suitable nesting beaches. Sexually mature crabs typically spend most of the year in deeper estuarine waters or on the continental shelf and migrate toward shore to nest during a limited period of each spring. Although wave surge and seafloor slope might potentially be used in finding the beach once crabs have arrived in close proximity to the shore, the deeper wintering grounds are likely devoid of these cues. Furthermore, Limulus has been frequently captured at depths where little or no light penetrates and many populations thrive in highly turbid estuarine habitats, greatly reducing the efficacy of visual landmarks as navigational guideposts. In principle, several non-visual environmental cues might guide horseshoe crabs from deep water to their nesting beaches, including auditory cues, depth cues, chemical signals, and the Earth’s magnetic field. Potential cues and navigational strategies that may function in the onshore migration will be discussed.