Largest Living Species
Smallest Living Species
South East Asia
South East Asia
Out of the four remaining species, Limulus
polyphemus is the largest and best known. Its geographical
distribution ranges between approximately 19° North to 42°
North along the east coast of North America. Ranging from Maine
in the far north to the Yucatan peninsula in Mexico, L. polyphemus
populations show a distinct latitudinal gradient, exhibiting
discrete genetic variation. The peak abundance occurs in Delaware
Bay, New Jersey, USA.
L. polyphemus are ecologically very important, its eggs
provide food for threatened loggerhead sea turtles, alligators,
wading birds and many fish species. Its foraging technique aerates
substrata thereby affecting infaunal communities. However there
has been an alarming decline in population numbers over the last
twenty years, threatening a diverse ecosystem. The decline has
been caused by the high commercial value placed on the organism.
The horseshoe crab has extensive pharmaceutical and biomedical
application. Compounds within its respiratory pigment are a vital
component in the manufacture of intravenous solutions, antibiotics,
and kidney dialysers. Currently there are no legal protections
for this species and no controls on horseshoe crab "harvesting"
thus potentially threatening the future of the species and an
(Photo by Peter Dyrynda 2003-04. Used
with permission according to the copyright terms and conditions)
which is also known as the "mangrove horseshoe crab"
is an Indian species and the smallest extant xiphosuran. Horseshoe
crabs are generally considered to be entirely marine though C.
rotundicauda has been recorded entering rivers in India and
was once caught 145 km (96 miles) upstream. This highlights its
ability to adapt to fluctuating conditions (salinity). Cladistic
analysis placed it closer to the tribe Tachypleus than L. polyphemus.
It is considered to be the sister taxon to the clade which includes
T. gigas and T. tridentatus, with L. polyphemus
most distantly related. As with L. polyphemus, its biomolecular
properties are used in the biomedical industry. Haemagglutinin
is extracted from the amoebocytes of the crab, which is used an
an arteficial blood clotting agent.
T. gigas which
is also known as the " coastal or
Singapore horseshoe crab" occurs around the coast of South
Asia. It is distinguished from its sister taxon T. tridentatus
by its size, colour, shape of the tail and the number of spines
at the base of the opisthosoma. Its ecology and serology are almost
identical. Populations have been severely reduced due to habitat
destruction and pollution, threatening the future of this species.
T. tridentatus is
also known as the "Chinese horseshoe crab" and is the
sister taxon to T. gigas. It is smaller in size and has
a serated telson. Its ecology and serology are almost identical
to T. gigas making it a valuble source to the biomedical
Author: Andrew Przewieslik
Last updated: 21/11/05
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