Sanibel Sea School Blog

A Pinch of Fun & A Dash of Claws – Spider Crab Week at Sanibel Sea School

June 21, 2022

Decapod or 10-legged crustaceans were the area of focus from June 13 to 17 during Sanibel Sea School’s Island Skills Summer Camp at the Flagship Campus. Two of those ten appendages are typically claws, or chelae, which are modified for different uses dependent on the species. Claws are used for feeding, defense, communication, mate attraction, burrowing, and more. After repeated observations of crabs using their claws in the field, campers learned how to make educated guesses about diet, defense strategies, and behavior.


Spider crabs were this week’s celebrity creature with the most effort focused on finding them. Two commonly found local species are the portly spider crab (Libinia emarginata) and the longnose spider crab (Libinia dubia). Using handy nets & snorkels, campers were also able to find stone crabs, hermit crabs, and multiple species of swimming crabs. A mud walk through the mangroves provided the perfect setting to observe fiddler crabs and mangrove tree crabs!


“The highlight of this week was definitely the mud walk,” said Marine Science Educator Brianna Machuga. “We were able to observe male fiddler crabs waving their oversized claw to attract mates. Campers were definitely pushed out of their comfort zones in knee-deep mud but we ended the walk with a nice dip into the bay to clean off.”


In addition to exploring all of Sanibel’s diverse habitats in search of crustaceans, counselors led campers through plenty of games and hands-on activities. In one experiment, campers used tweezers, claw crackers, hair clips, chopsticks, and pipe cleaners to try to pick up different “prey” items like gummies, sand, cotton balls, and shells.


Each tool represented a different claw shape from species like spider crabs, stone crabs, swimming crabs, and mole crabs while the prey items represented fish plankton, algae, bivalves, and gastropods. Campers determined what the likely prey of each crab was based on the success of each “claw.”

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