Field marks: The Spider Crab
was sandy brown in color
except for it was white on its ventral
belly. The dorsal side was
bumpy and the texture was similar to sand. The crab has eight legs but two
were missing so it only had six. There are two front leg-like structures that
have pinchers on the end to aid
in eating.
Size: Field measurements were
taken for the size of the Spider Crab and are the following:
Head to anus- 2.5 inches
Leg length- 3 inches
Body Width- 2 inches
General habitat: Our observations
confirmed that the Spider Crab dwells in low tide regions. In reality, they
can be found anywhere from low tide to 400 feet deep ocean water.
Geographic range: Found
along East coast, but most common in southern waters
Ecosystem(s) where observed: Shallow
inter-tidal region at Lulu Island
Field Observations: The first
observation that we took on the Spider Crab was its amazing ability to blend
in with the surrounding sand of the intertidal zone. When approaching
this fine creature, it appears to be a small rock in the water but with close
observation, the outline of its legs can be observed. After further observation,
it was found that the crab buries itself with its legs into the sand and make
only its sand textured dorsal side visible. The Common Spider Crab was found
in a depth of about eight inches and about 100 yards off the shore in the
Gulf of Mexico. After picking it up, the crab showed
aggression and strength in the six of its eight legs. At one point it
even pinched one of us and left a small laceration. As stated above, two of
the eight legs of this Spider Crab were missing. The two that were missing
were the middle two on the right side. The ability of the crab to lose its
legs may have saved its life from a predator. The mouth of the crab was also
very interesting and highly complex. Two plate-like structures seemed to control
the movement of the mouth and its ability to open and close. Inside the mouth,
very mall arm-like structures moved frantically to grab at anything that would
enter. Other observations show that when walking, the Spider Crab travels
forward and sideways at the same time. The Spider Crab is a great marine organism
and worthy of further study.
References: Alden P, Cech R, and G Nelson.
National Audubon Society Field Guide to Floridaö. Alfred A. Knopf: New
York, 1998. p. 207.
