Biological Sciences REPRODUCTIVE ECOLOGY OF THE AMERICAN HORSESHOE CRAB LIMULUS POLYPHEMUS IN THE INDIAN RIVER LAGOON: AN OVERVIEW

Horseshoe crabs, Limulus polyphemus, typically inhabit estuaries with pronounced tides that influence the timing of reproduction. However, many of the cues known to mediate spawning and larval hatching are absent in the Indian River Lagoon (IRL) since much of the area is microtidal. This review summarizes our recent studies of the reproductive ecology of L. polyphemus in the IRL that focused on the potential impact of microtidal conditions on the timing and frequency of mating, spawning, and larval hatching and abundance. Extensive surveys conducted throughout the northern region of the IRL indicated that spawning occurs year-round but is aperiodic. Throughout the sampling period, larval abundances were low, despite the fact that environmental conditions were suitable for their survival and development. Peaks in larval abundance were independent of spawning events but were linked to changes in water level. Laboratory experiments indicated that conditions associated with periods of high water, including inundation and mechanical agitation, may facilitate hatching, resulting in short-term peaks in larval abundance. In general, the reproductive ecology of L. polyphemus in the IRL differs markedly from populations in tidal areas. However, results indicate that spawning and larval hatching are cued by environmental conditions that are similar to those associated with tidal changes.