File:Coast watch (1979) (20038390644).jpg

English:
Nancy Targett, a University of Delaware marine biologist, says local watermen are dependent upon harvesting horseshoe crabs as bait for lucrative fisheries

Title: Coast watch
Identifier: coastwatch00uncs_16 (find matches)
Year: 1979 (1970s)
Authors: UNC Sea Grant College Program
Subjects: Marine resources; Oceanography; Coastal zone management; Coastal ecology
Publisher: (Raleigh, N. C. : UNC Sea Grant College Program)
Contributing Library: State Library of North Carolina
Digitizing Sponsor: North Carolina Digital Heritage Center

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NATURALIST'S NOTEBOOK Again, despite the deadly reputation of the arachnids, the horseshoe crab is indeed a gentle creature. Unless you are a mollusk — mollusks are this so-called crab's main food source — horseshoe crabs can be quite inspiring. Experiencing their benign nature may cause one to yearn for an equally calming and harmless nautical existence. THE LIVING FOSSIL' The lineage of the horseshoe crab is one of the most amazing aspects of the animal. The genus Limulus originated in the Triassic period, which is the first period in the age of the dinosaurs. And its ancestors — trilobites — were dominant Earth creatures 100 million years before dinosaurs even existed. Not only has the horseshoe crab evaded extinction over millions of years of evolution, but the genus Limulus has evolved very little throughout history. "Horseshoe crabs are ecological generalists: they can withstand a wide range of conditions, natural as well as man-induced." And their ".. .jack-of-all-trades nature.. .holds the clue to why they have remained so stable, so evolutionarily unchangeable for hundreds of millions of years," writes Niles Eldredge in his book Fossils. LIFE CYCLES OF THE BROWN AND SCARY You'd be lucky to come across live horseshoe crabs on the beach outside of their spring spawning season. They are benthic creatures, preferring a lifestyle adapted to offshore habitats near the continental shelf, as well as shallow estuarine areas. The horseshoe crab is generally nocturnal. When active, it may swim upside down or burrow and crawl along the sandy ocean floor in search of invertebrate prey. Upon finding its meal, the horseshoe crab grinds the sea worm or whatnot with the base of its legs, and then pushes the ground food into its mouth with, again, its all-purpose legs. If, by chance, the crab becomes overturned, it can use its telson, or tail- like appendage, as a tool for flipping back to a more comfortable position. Of the four remaining species of the ancient horseshoe crabs, three inhabit waters along the coasts of India Japan and Indonesia. Limulus polyphemus, the fourth and most abundant species, exists along the Atlantic coast of North America. Its range extends from northern Maine to the Yucatan Peninsula with the largest population of Limulus occurring along the Delaware Bay. The Delaware Bay is home to the largest population of horseshoe crabs in the world, regardless of species. And is a main breeding site, where thousands of horseshoe crabs travel to shore at high tide during a new and full moon. The smaller males attach to the females' carapace and hitchhike onto shore with flooding tides. Once a couple reach their destination, the female digs a nest, in which she can produce up to 88,000 eggs. Several males may crowd to fertilize the nest in the process. Since it takes female horseshoe crabs about 10 years to reach sexual maturity — males average eight years — the amount of eggs is not excessive. This is especially true if the eggs become exposed to the sandy shore surface and therefore vulnerable to a variety of predators, such as small fish, juveniles of larger fish and shorebirds. In the Delaware Bay area alone, close to a million migratory shorebirds have coevolved with horseshoe crabs. "Horseshoe crabs are critical to the welfare of migrating shorebirds
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