Fun Facts
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It has been estimated that whelk fishermen
use 20,000 to 25,000 horseshoe crabs per year as
bait.
Both New Jersey and Georgia have adopted
the knobbed whelk as their state shell. |
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In Japan, eels are traditionally eaten on the Day of the Ox to replenish energy for the hot summer months to come. Rich in Vitamin A and protein, eels have a high nutritional value. |
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American Indians
called this unique critter a "Se-ekanau." In 1588, British naturalist
Thomas Hariot called it the "horsefoot" crab — probably
because the shape of the crab resembles the foot of a horse.
Somehow, through time, horsefoot was corrupted to "horseshoe."
Despite its threatening appearance, the horseshoe crab is harmless, and its long, spike-like tail is not poisonous, as people may think. The crab uses its tail as a lever to right itself when it has been overturned by a wave or a thoughtless person. The horseshoe crab may be harmed if handled by the tail. In additon, the claws of a horseshoe crab are not sharp and do not pinch very hard. |
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Kabutogani is the common name for Tachypleus tridentatus, the species of horseshoe crab inhabiting Japan. This horseshoe crab is also called hachigame, dongame, or hachigani in Japanese.
Each spring, kabutogani appear on the shores of the Seto
Inland Sea. Migrating from their winter hideaways, they
return to the islands of Kyushu and Honshu to lay their
eggs. Unlike its American cousin, Limulus polyphemus, T.
tridentatus nests in shallow water near shore. Like
swans, each nesting pair is monagomous. They choose their
mates for life.
Although slightly larger in size, the Japanese horseshoe crab closely resembles Limulus polyphemus. |
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Why do horseshoe crabs lay so many
eggs? It's a numbers game in the quest for survival. After
laying her eggs, the female horseshoe crab crawls away,
leaving the shallow nest unattended. Predators and natural
conditions take their toll on the developing eggs, trilobite
larvae, and young horseshoe crabs. Only a very small percentage
actually grow to reach adulthood and engage in reproductive
activity.
Other animals have a different reproductive strategy. Take people, for example. Offspring numbers are very low compared to horseshoe crabs, but the parents put more energy into helping them survive and grow. Either way, the biological goal is to ensure that enough offspring survive to reproduce and continue the generations! |
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Two of the Asian species of horseshoe crabs, Carcinscorpius rotundicauda and Tachypleus tridentatus, are considered a delicacy in China, Hong Kong, and Vietnam. Harvested by local fishermen or imported from China and Malaysia, female horseshoe crabs are prized for their eggs and large quanitity of meat.
Worth only one to two dollars as
bait for eels and conch in the United States, pre-cooked
female horsehoe crabs sell for $200-400 HK ($25-50 US) in Hong Kong
seafood shops. Street market prices are slightly lower, between $45-100 HK ($6-13
US). |
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The circulatory fluid, or hemolymph, of
horseshoe crabs is analogous to human blood. The horseshoe
crab's blood is blue due to a chemical reaction between
copper and an oxygen-carrying protein called hemocyanin. In
order to transport oxygen from enriched areas (gills) to
depleted areas (tissues), copper ions must first bind chemically
to the protein. The oxygen in the protein then binds to
the copper ions, and the resulting complex becomes blue.
When oxygen is not present, the hemolymph is colorless.
In humans, the oxygen-carrying proteins (hemoglobins) in
blood bind with iron molecules. Iron gives oxygenated human
blood its characteristic red coloration. |
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As a species, ruddy turnstones play an important role in the ecology of the Delaware Bay. Using their strong bills as shovels, or more accurately, brooms, they dig holes in the sand, exposing buried horseshoe crab eggs and making them available as food. Some holes extend two or three inches beneath the surface. Each bird vigorously defends its hole against other shorebirds until it has eaten the eggs exposed inside. Then it moves on to start another. After a turnstone leaves, however, there are often pickings left for other species. A succession of species often follows the initial ruddy turnstone digger. |
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