When we talk about various crab types, in total we are referring to almost 5,000 different species. However, not all these species are considered as "true" crab. There are about 4,500 species of true crab ,and the remaining 500 species are Hermit crab. The reason behind not including these in the "true crab" category is because they don't have a tough shell of themselves, but use other animals' old shells as their own protection. Along with Hermit crab, even King crab, Horseshoe crab, and Porcelain crab are not from the true species.
Over centuries, these animals have evolved to the extent that they can walk sideways, swim and burrow as well. The body is generally covered with a semi-transparent shell, which is called a carapace. Their abdomen have reduced over time and are tucked underneath their body. "True crab" have seen this reduction for the most part, as they don't have the flap-like tail, more commonly found in the Hermit crab. They have 5 pairs of appendages that are utilized as legs and other 2 in the front as sensory antennae. These animals are usually aggressive towards each other, and male crab tend to fight one another so that they can gain access to the females for mating.
What are the Different Types
As there are numerous species found across the globe. Hence, listing them all together can be difficult. However, the following information will provide you interesting facts, their characteristics, diet, and habitat.
- As the name suggests, green crab are dark green with yellow or sometimes brown blotches all over their body. Underneath, however, these animals are orange-red in color.
- They have 5 spines (points) along their square-shaped shell.
- Some of these animals can delay shedding and hence turn red in color. "Converted" crab tend to be stronger and more aggressive.
- Their ideal diet consists of plants and a wide variety of marine animals like mussels, clams, snails, isopods, and barnacles.
- Any type of seashore in shallow waters and upstream river mouths are ideal for their habitat.
- The female can lay nearly 185,000 eggs.
As their name suggests, these arthropods have similar shape of a horseshoe and are related to spiders and scorpions. They are also called "living fossils" and are brown in color. They swim keeping their bodies upside down and migrate to shallow waters for mating and laying their green eggs. They are most likely to be found in Gulf of Mexico and northern Atlantic coast of North America.
- They can live up to 20―25 years and in late spring, tend to migrate in the shore.
- They have 5 pairs of book gills behind their appendages. This is what allows them to breathe underneath the water and breath on land (short periods).
- Their diet consists of annelid worms, shellfish, and benthic invertebrates.
- Any type of offshore along the coast and lower ends of rivers, which meets the sea, coves, bays, small inlets of sea and shallow water lands are ideal for living.
- A female can lay from 15,000 to 64,000 eggs (depending on the size of the female body).
- Young Spider crab have hair and thorns on their shells, with long horns in the front.
- The bottom of the Pacific Ocean which is situated around the Japanese archipelago is an ideal habitat.
- The diet consists of dead fish, algae, plants, shellfish and starfish.
- Their life expectancy is up to 100 years, and is also referred to as a "living fossil".
- Abdomens of the female are wider than the male, and they tend to lay eggs shortly after mating is done.
Red Rock Crab
Also called the Sally Lightfoot crab and red cancer crab, these animals are found along the coast of north-east Pacific waters, Central America, Galapagos Islands, and Mexico. Young red rock crab come in black or brown colors, whereas the adults come in brown-red with brown, pink, or yellow spots all over their body. Some tropical island crab are also found in bright red or orange colors with blue and green stripes, red claws, and pink or blue eyes.
- They have a short life span of 5―7 years only.
- Any low intertidal zones, gravel bays, rocky areas, locations with eel-grass growth, and water levels up to 260" deep are ideal for their habitat.
- The diet consists of algae, plants, mussels, clams, snails, and dead fish.
- They stay active mostly at night and mate between July and August.
They have the ability to survive in extreme locations as well, because they can adapt to the ever-changing environment around them. Typically, these animals work in groups to provide food and shelter for their family and help find a comfortable location for the females to lay their eggs.