What is a Crab?

1. What is a Crab? Even though some crabs are different from others, they all have several things in common: Crabs are crustaceans just like shrimp barnacles, and lobsters. Crabs have 10 jointed legs. True crabs can only walksideways, and sometimes backwards. Crabs are hard on the outside…not like us! We have hard bones on the inside (endoskeleton) and crabs have a hard shell on the outside (exoskeleton).

2. A Crab’s Body Eyes – They stick out! Antennae – To feel and smell. Claws – To help the crab eat and for protection. Watch out for these! Legs – Some to walk and others to pinch. Can you count all 10? Carapace – The hard shell covering the body. Telson – the tail that is always tucked underneath.

3. What is Molting? Just like we outgrow our old shoes, crabs outgrow their hard shell! Crabs have to molt their entire outer covering in order to grow. The old shell that they leave behind is called a molt. These hard molts look like dead crabs, but the real crab is still alive! But How? When it is time for the crab to molt, they wriggle out of their old shell, then grow a new bigger one. Look around the beach—can you find any crab molts?

4. How do Crabs Breathe? Just like fish, crabs use gills to breathe. Crabs can only breathe as long as they stay wet. A horseshoe crab has book gills. When underwater the gills flip like the pages of a book. Can you see them in this picture? Fiddler crabs are special because they can use the air to breathe, just like us!

5. What do I look like? Just like there are 5 letters in the word green, I have 5 “teeth” along each side of the front of my carapace. I can be many colors including red, orange, and green. European Green Crab Where do I live? Beaches, estuaries, and tidepools. What likes to eat me? Sea birds. What do I eat? Soft-shell clams, oysters, mussels, and worms. What makes me special? I am originally from Europe but have been on the east coast of the USA since 1817

6. Asian Shore Crab What do I look like? I have 3 “teeth” or spines along the two sides of my carapace and my carapace is shaped like a square. Where do I live? First I start in the rocky intertidal, then I slowly spread into salt marshes. What do I eat? Grass, algae, fish, snails, worms, mussels, clams, and oysters. What makes me special? I am originally from Asia but in southern New England, I can be found at densities as high as 80 per a square meter. What likes to eat me? Being eaten is rare but if I am it is usually by rockfish, sea gulls, and other crabs.

7. Jonah Crab What do I look like? I have 9 jagged “teeth” along each side of the carapace. I look a lot like the Rock Crab. Where do I live?Tidepools and deeper water down to 2000 feet! What do I eat? Mussels, snails, barnacles, detritus (dead plants and animals), and other crabs. What likes to eat me? Because of my hard shell… only humans. What makes me special? Although I am native species, you will be lucky to find me anywhere in the intertidal.

8. How to identify crabs • Worst way: Color of the crab. To illustrate this, both the crabs on this slide are “Green Crabs” • Best Way: By counting the number of marginal teeth. • Marginal teeth are the spines, “teeth”, ridges, or notches on the front of the carapace to each side of their eyes.

9. Color of the “Green” Crab

10. My carapace (shell) is boxlike, and smallest crab in the rocky intertidal, only three “teeth” on each side of its eye. My legs also have black bands and males have a bulbous membrane or a “fleshy bubble” in the middle of their claws (chelipeds) as shown the right. My carapace is more rectangular and fanlike and the crab has five “teeth” on each side of its eye. Once I get large, the spines are quite distinct and clearly defined. When I am juvenile, I can have white and orange patterns. Asian Shore Vs. Green Crab

11. The rock crab is bigger than the introduced Asian and green crabs. It is usually red and has nine well defined “teeth” and black tipped claws. “J” for “Jagged” and ”“Jonah”. This crab looks identical to the rock crab except its “teeth” are less distinct, more jagged, frilly, serrated like a saw blade. Rock Vs. Jonah Crab

12. Introduced and Invasive species • Introduced species are any organism that has moved to a place it was not before. • Invasive Species are a subset of the introduced species that cause ecological and/or economic damage. • Three examples include the European green crabs (top), periwinkles (middle) and the Asian shore crab (bottom).

13. Is it Male or Female? Look at the tail on the bottom of a crab or molt. (The tail, or telson, is folded against the abdomen) Male crabs have a narrow tail. It may be in the shape of a rocket ship. Female crabs have a wide tail so that she can hold her eggs.

14. How to pick up a crab, safely! • The best way to pick up a crab is to put your thumb and first finger on or behind the furthest “tooth” away from the eye. The crab does not have the dexterity to reach around and pinch you!