Crustaceans | Earth Day Network

What You Need to Know About Crustaceans and Why We Need to Protect Them

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.[1]
  • 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).[2]
  • 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.[3]
  • 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.[4]
  • 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.[5]

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.[6]
  • 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.[7]
  • 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.[8]
  • Uniqueness While most crustaceans reproduce sexually with a separate male and female, barnacles are hermaphrodites that reproduce asexually by producing both eggs and sperm.[9]

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.[10]
  • Coral Reef Loss: As crustaceans depend on coral reef communities for shelter, the decline of coral reef populations also threatens.[11]
    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.[12]
  • 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.[13]

What You Can Do to Help Protect Crustaceans

  • Make safe and sustainable seafood choices. A wide variety of fishing gear and techniques are used to catch fish and seafood. Each method has an impact on marine life and the ocean. Buying seafood caught or farmed in environmentally sustainable ways supports healthy marine ecosystems and protects marine species. To get started, check out a list of organizations that offer sustainable seafood resources across the world.
  • Support and defend the Endangered Species Act which currently protects twenty-two crustacean species.
  • Test your knowledge about threats to ocean ecosystems with our Oceans Plastic Pollution Quiz.
  • Take personal steps to end plastic pollution.