The delaware bay area, U.S.A.: A unique habitat of the American horseshoe crab, Limulus polyphemus

Abstract

Continuing the theme developed by Shuster and Botton (Estuaries 8:363#x2013;372, 1985) on the dynamics of the Delaware Bay population of Limulus polyphemus and by Sekiguchi and Shuster (Limits on the global distribution of horseshoe crabs (Limulacea): lessons learned from two lifetimes of observations: Asia and America. In: Tanacredi JT, Botton ML, Smith DR (eds) Biology and conservation of horseshoe crabs. Springer, New York, pp 5#x2013;24, 2009) on global limits on the distribution of horseshoe crabs and by Shuster and Sekiguchi (Basic habitat requirements of the extant species of horseshoe crabs (Limulidae). In: Tanacredi JT, Botton ML, Smith DR (eds) Biology and conservation of horseshoe crabs. Springer, New York, pp 115#x2013;129, 2009) on local habitat requirements, this paper considers why the Delaware Bay is the epicenter of Limulus polyphemus abundance. The emphasis is on how its geologic and geographic characteristics are advantageous to Limulus. Although the species ranges along the east coast of North America from Yucatan, Mexico to Maine, USA (21#x00B0;N to 44.5#x00B0;N), only at Delaware Bay (38#x00B0;40#x0027; N to 39#x00B0;20#x0027; N) has it produced a population of millions of adult horseshoe crabs, unmatched anywhere. Why? It appears most likely that it was the interaction between the ecological generalist, Limulus polyphemus, and the exceptionally favorable environment that developed in the Delaware Bay area after the past great ice age. However, this productive relationship is short-lived. Chronologically the bay will be shorter-live with a probable existence of some 85,000 years, while Limulus polyphemus may have already existed some 135 million years.