Descriptive
Information
- Field Marks:
Horseshoe shaped carapace, triangular abdomen, long tail,
brown, 2 eyes, fuzzy mouth, 5 pairs of walking legs, 2 pinchers
in front.
- Size:
- Female: 18 inches
- Male: 12 inches
- General
Habitat: Mud and sand bottoms to 75 feet deep
- Range:
Gulf of Mexico, U.S. Coastline
- Field Observations:
On our canoe trip out to Lulu Key we took a break at a sand bar.
It is here where we first encountered an Atlantic Horseshoe Crab
(an ancient species, fossil record). When we examined this arachnid
we noticed several different characteristics. The outer covering
(carapace) was brown and very hard. Also it had 2
eyes at the front and they were set far apart. On the underside
of the crab we found 5 pairs of walking legs and one pair of pinchers
in front. The male
has a specialized pair of pinchers for mating. The fuzzy mouth is
in the center, therefore, the different appendages bring the food
to it. This crab also has a triangular abdomen. The abdomen and
carapace are at a hinge. The Horseshoe Crab also has a long
hard, pointed tail. This tail is used to flip the organism over
when it is upside down. It does so using circular motion of the
tail. Atlantic Horseshoe Crabs mate in early spring, at high-tide
lines (especially on a full moon tide). The larger female
releases a pheromone to attract the male. The male grabs onto the
female via his specialized pinchers. The female moves to the highest
point of the tide and digs
a hole half a foot deep. Into this hole she releases 200 blue-gray
tiny eggs. Along with the eggs she releases another pheromone that
causes the male to release sperm. The eggs are then covered by the
incoming tide and the two organisms "unlatch" and go they're
separate ways. This is external fertilization. We caught two Horseshoe
Crabs mating
on Lulu key at night, but when the lantern light was on them, they
moved towards the water. But when the light was no longer on them
they moved back to shore. During our observation of the two we accidentally
detached the two. The male went back into the water, while female
continued to dig a hole.
- Sources:
- Alden, P. National Audubon Society Field Guide To Florida.
Alfred A Knopf, New York. 1998. Pg 204.
- Kaplan, Eugene. Southeastern and Caribbean Seashores. Houghton
Mifflin Company. Boston. 1998. Plate 25-26.
- Video
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