Facts About Crustaceans
- Crustaceans are members of a massive category of animals known as arthropods, categorized by their exoskeletons and jointed limbs. Crustaceans are also some of the oldest animals on Earth, with evidence of their exoskeletons being recorded all the way back to the Cambrian Period nearly 540 million years ago.
- There are more than 50,000 known species of crustaceans. These species are divided into a number of major groups: The Branchiopods, the Maxillopods, the Ostracods, and the Malacostraca.
- Crustaceans are found in a diverse range of habitats. Most are freshwater or marine animals, but some are terrestrial or do not move (e.g., barnacles).
- Crustaceans range in size considerably, from the Japanese spider crab with a leg span of 4.3 meters, to a parasite of copepods, which is only 0.1 millimeters long.
- Decapod crustaceans communicate by flapping their pincers or drumming their claws. They will also use their pincers or claws to fight for the best hiding spots, provide food for their young, and as protection.
- There is a direct correlation between the health of reefs and the population of crustacean species. The decline of reefs from human activities is causing a decrease in the biodiversity of crustaceans.
Why We Need to Protect Crustaceans
- Role in the Ecosystem: Crustaceans play an important role in the ecosystem by serving as vital food sources for marine animals. Small crustaceans can recycle nutrients as filter feeders and larger crustaceans can act as a food source for large aquatic mammals. Terrestrial crustaceans also have ecological importance as decomposers of dead organisms.
- Ecosystem Services: By eating substantial amounts of algae, small crustaceans keep the plants in check, which keeps the clears the water and gives seagrass beds access to light and oxygen.
- Economic Contributions Crustaceans are considered economically important to humans because of their large role in marine and terrestrial food chains. Crustaceans play an important role to economies in coastal areas like the Chesapeake Bay, an estuary in the U.S. states of Maryland and Virginia. In 2009, the dockside value of the blue crab harvest Bay-wide was estimated at $78 million. As a result of the decline of crabs in the Bay, there has been a cumulative loss of about $640 million in Maryland and Virginia combined.
- Uniqueness While most crustaceans reproduce sexually with a separate male and female, barnacles are hermaphrodites that reproduce asexually by producing both eggs and sperm.
Threats to Crustaceans
- Ocean Acidification: Changes in the chemical makeup of oceans caused by climate change is making it difficult for crustaceans like lobsters and crabs to grow their shells. This can disrupt marine food chains by making crustaceans more vulnerable to predators.
- Coral Reef Loss: As crustaceans depend on coral reef communities for shelter, the decline of coral reef populations also threatens.
Overfishing: Overfishing of krill has increased in the Antarctic Ocean in recent years and has placed pressure on sensitive ecosystems in the ocean. Krill, a small crustacean, plays an important role in the food chain in the Antarctic ocean by feeding penguins, seals, whales, fish, and birds.
- Plastic Pollution: Microplastics — pieces of plastic less than five millimeters long — are ingested by crustaceans and take six times longer to leave the body than digestible food. Because microplastics are retained longer within the crustacean, there is also an increased risk of biomagnification through the food chain.
What You Can Do to Help Protect Crustaceans
- Support sustainable fisheries: Overfishing can deplete the population of crustaceans beyond the point of recovery. By buying crustaceans from certified sustainable sources, you can help ensure that these marine creatures and their ecosystems continue to thrive. Learn more about the different types of eco-labeling here.
- Check out all of Earth Day Network’s resources to help Protect Our Species.
- Educate yourself about the threats to ocean ecosystems with our Oceans Plastic Pollution Quiz.
- Help end plastic pollution by learning about actions you can take and using our plastic pollution calculator to reduce your own waste.