What Is a Horseshoe Crab?
The horseshoe crab belongs to the large group of invertebrates (animals without backbones) called Arthropods. This group also includes lobsters, crabs, insects, spiders, and scorpions. Even though it looks crab-like, with a hard shell and claws, the horseshoe crab is more closely related to scorpions and spiders.
Horseshoe crabs, common along the Delaware coast, have evolved little in the last 250 million years. Still, they have survived because of their hard, curved shells, which have made it difficult for predators to overturn them and expose their soft, vulnerable underbellies. The horseshoe crab has also survived because it can go a year without eating and endure extreme temperatures and salinity.
Horseshoe Crab Facts & Figures
Despite their size and intimidating appearance, horseshoe crabs are not dangerous.
A horseshoe crab's tail, while menacing, is not a weapon. Instead, the tail is used to plow the crab through the sand and muck, to act as a rudder, and to right the crab when it accidentally tips over.
The horseshoe crab's central mouth is surrounded by its legs and while harmless, it is advisable to handle a horseshoe crab with care since you could pinch your fingers between the two parts of its shell while holding it.
Horseshoe crabs have 2 compound eyes on the top of their shells with a range of about 3 feet. The eyes are used for locating mates.
Horseshoe crabs can swim upside down in the open ocean using their dozen legs (most with claws) and a flap hiding nearly 200 flattened gills to propel themselves.
Horseshoe crabs feed mostly at night and burrow for worms and mollusks. They will, however, feed at any time.
Horseshoe crabs grow by molting and emerge 25 percent larger with each molt. After 16 molts (usually between 9 and 12 years) they will be fully grown adults.
Horseshoe crab eggs are important food for migratory shore birds that pass over the Delaware Bay during the spring mating season. Fish also eat the juveniles or recent molts.
In the 1900s, horseshoe crabs were dried for use as fertilizer and poultry food supplements before the advent of artificial fertilizers.
The medical profession uses an extract from the horseshoe crab's blue, copper-based blood called lysate to test the purity of medicines. Certain properties of the shell have also been used to speed blood clotting and to make absorbable sutures.
Jul 09, 2008 @ 06:09:36
