Crustaceans

Blue Crab

Blue crab (Callinectes sapidus) lives through the Atlantic Coast and in the Gulf of Mexico. The blue crab shell, also called a carapace, is blue to olive green, the shell can reach 9 inches across. The claws are bright blue, with mature females having red tips on the claws as well. They have four pairs of legs, the first three are walking legs, while the last rear pair are swimming legs that look like paddles.
Blue crabs can live up to 3-4 years, reaching maturity at about 12 to 18 months. Water temperature does affect growth rates, they grow more quickly in warm waters. In the Gulf of Mexico, they can mature in about a year, but in the Chesapeake Bay, it can take up to 18 months. As the crab grows, it will “molt”, which is shedding its hard shell. When molting occurs, they will lose their hard parts, which can make it difficult to determine age. Males will molt multiple times during their lives, while females will only molt once, which is before mating. Blue crabs are bottom-dwellers, beds of submerged aquatic grasses are used for food, nursery habitat for young, and shelter during mating and molting.
These shellfish are important predators of benthic communities and are prey for many fish species. They will eat almost anything, including clams, oysters, mussels, smaller crustaceans, freshly dead fish, plant, and animal detritus, and other blue crabs that are smaller and soft-shelled. Crabs become prey to large fish, some fish-eating birds, such as great blue herons, and sea turtles.
When mating occurs, a male will cradle a female in a pose known as a “doubler” for a few days before her last and only molt. The male will stay with her after mating until her shell hardens, to ensure no other male will mate with her. When the eggs hatch the larvae will go through multiple molts in high-salinity coastal waters.
Cool Fact! Callinectes sapidus is translated from Latin which means, ‘beautiful savory swimmer’.
Photo Credit: Bobby Putnam
Author: Destiny Alvarez – Fisheries and Wildlife Sciences, University of Oregon
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Fiddler Crabs

Fiddler Crabs (Genus uca) live in the tidal sands of mangroves and salt marshes. They are experts at sensing the ebb and flow of the tide because their survival depends on it. Although they have gills, Fiddler crabs can drown if there is too much water. They retreat to their 12″ burrows in the sand at high tide and seal the burrow with mud or sand.

During low tide, Fiddler Crabs colonies get down to business doing their part for the ecosystem when they come out in the hundreds to work and eat. To build and maintain their burrows, they use their small claws to move sand to their mouths, where they strain and extract nutrients. Clean sand pellets are spat out. Although their diet consists of algae and decomposed matter, Fiddler Crabs are tasty meals for shorebirds, fish, and land mammals such as raccoons and foxes.

Female crabs incubate eggs for 2 weeks. During high tide, the female will release the larvae who will float away. In a few weeks, the surviving young crabs will drift back to shore and join a Fiddler Crab colony.

Male Fiddler Crabs have one oversized claw that looks like a fiddle. While it is sometimes used to defend against other male crabs, the large claw is primarily used in courting rituals. To woo his desired female, the male Fiddler crab will dance while waving his giant claw until the lady agrees to join him in his burrow.

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Sand Crabs

Sand Crabs are also known as mole crabs or sand fleas. These crustaceans are smaller than a human thumb. The two species predominant on Florida beaches are Emerita talpoida and Emerita benedicti. They are silvery or white in color and seem transparent. The Crabs have antennae, which they use to catch plankton for food. They have no claws and do not bite or sting. The Sand Crabs live between two to three years. The crabs are food for fish, Florida shorebirds, and water birds. They feed on micro-organisms found in the Florida beach sand. That means that they ingest any toxins that might be affecting the shore or the water. Environmental engineers and scientists are able to conclude the health of the ocean based on the condition of sand crabs.

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