American Oceans

Types of Crustaceans to Know

You may know that crustaceans are invertebrates that are a part of the subphylum Crustacea, but there are many interesting facts about each type of crustacean.

clown mantis shrimp

This article will explore the fascinating world of crustaceans, their physical appearance, habits, and other fun facts.

Crabs

Peekytoe Crab or Atlantic Rock Crab underwater

Number of Species: 4,500 – 6,700
Notable Species: Dungeness Crab, Hermit Crab, Horseshoe Crab, King Crab, Japanese Spider Crab 

Crabs are fascinating crustaceans known for their unique appearance, diverse species, and ecological importance.

Depending on the species, crabs exhibit various diets, from omnivorous to specialized feeders. Depending on the species, they are land, freshwater, and marine animals.

People harvest many crab species for their delicious meat, making them essential in the seafood industry. Horseshoe crabs are also used in biomedical research due to their unique immune system and blue blood.


Lobsters

largest maine lobster photo of existence underwater

Number of Species: 75
Notable Species: American Lobster, European Lobster, Nephropsis rosea

Lobsters are large marine crustaceans, and two notable species include the American lobster (Homarus americanus) and the European lobster (Homarus gammarus). They have a long body, a hard exoskeleton, two large claws, and numerous legs with joint appendages.

Lobsters are typically found in rocky reefs, coastal habitats, and kelp forests, and they are opportunistic predators that feed on different types of prey, including fish, mollusks, and crustaceans. Also, they have complex rituals and the ability to regenerate lost limbs.

Like crabs, they have significant economic value and are commercially harvested for their meat. They are considered a delicacy in many cuisines and are used in various culinary dishes.


Crayfish

a crawfish on the ground holding its pinchers up

Number of Species: 640 
Notable Species: Louisiana/Red Swamp Crawfish, Murray Crayfish, Signal Crayfish, White-Clawed/European Crayfish

Crayfish, a.k.a. Crawfish or Crawdads, are freshwater crustaceans from the Astacidae family. They’re known for their distinctively large pincers in various habitats, including streams, rivers, lakes, and swamps.

Crayfish exhibit a diverse diet, feeding on various organisms such as insects, small fish, and plants. That said, they have important ecological roles as prey and predator and are also popular in the aquarium trade.

Some crayfish species are also fished commercially for human consumption, particularly in North America and Europe.


Krill

a single antarctic krill

Number of Species: 86
Notable Species: Antarctic Krill, North Pacific Krill

Krill are small shrimplike crustaceans that live in huge swarms in the open ocean. They’re an essential part of the marine food chain and are vital species in Antarctic ecosystems.

Krill typically feed on phytoplankton, zooplankton, and other small animals, although some species are omnivores. Krill also play a significant role in the global carbon cycle by transporting organic matter from surface waters to deeper ocean layers.

Commercial fisheries harvest krill for various products, including omega-3 fatty acid supplements and livestock feed.


Shrimp

a cleaner shrimp underwater

Number of Species: Approximately 2,000
Notable Species: Atlantic White Shrimp, Pacific White Shrimp, Royal Red Shrimp

Shrimp are small, slender crustaceans closely related to lobsters and crabs. They have long bodies with five pairs of legs and antennae, and they can be found in estuaries, rivers, and lagoons, but they are mainly found in the ocean.

Shrimp feed on a wide range of organisms, from zooplankton to detritus, and they are important prey for larger predators. They also act as scavengers, helping to clean up detritus from the ocean floor.

Shrimp are popular seafood items, and they’re widely harvested in commercial fisheries. 


Prawns

fished and captured the biggest shrimp and prawns

Number of Species: 3,000 
Notable Species: Giant Tiger Prawn, Banana Prawn, Red Spotted Shrimp

Prawns are a group of large crustaceans closely related to shrimp. They have long, slender bodies and distinctively large heads with large eyes, two pairs of antennae, and five pairs of legs.

It’s important to note their gill structure when distinguishing between prawns and shrimp. Prawns are characterized by their branching gills, while shrimp feature lamellar gills. This subtle difference helps to differentiate between the two types of crustaceans in a professional manner. 

Prawns are usually found in shallow coastal waters, estuaries, and rivers, feeding on animals like shrimp, mollusks, worms, detritus, and plankton.

Prawns are harvested commercially and recreationally; like shrimp, they are a popular seafood item.


Isopods 

a pillbug

Number of Species: 10,000
Notable Species:  Common Woodlouse, Giant Isopod, Roly-Poly

Isopods are a group of crustaceans that includes woodlice and pillbugs. These tiny crustaceans belong to the order Isopoda, and they are known for their segmented bodies and seven pairs of legs.

Depending on the species, isopods are marine and terrestrial crustaceans but are generally associated with moist habitats. They are typically scavengers or detritivores, feeding on decaying organic matter, dead animals, and plants.

Some species of isopods are also known to be parasitic, attaching to other marine organisms and feeding on their host’s tissues. 


Barnacles

Closeup of Acorn barnacles

Number of Species: 14,000 
Notable Species: Semibalanus Balanoides (Acorn Barnacle), Amphibalanus Amphitrite (Acorn Barnacle), Amphibalanus Improvisus (Bay Barnacle)

Barnacles are crustaceans that belong to the barnacle subclass Cirripedia. They have a hard shell made of calcium carbonate plates, which protect the body from predators and environmental conditions.

Barnacles are usually found in shallow waters attached to hard surfaces like docks, ships, rocks, and shells. They feed by extending their feathery legs into the water to filter out plankton, bacteria, and other small particles.

Barnacles are critical marine animals, providing habitat for other species, such as fish and polychaete worms. Unfortunately, they play a troubling role in biofouling, as they attach to ships and other human-made structures, leading to operational problems.


Horseshoe Shrimp

Number of Species: 13 
Notable Species: Sandersiella acuminata, Lightiella incisa, Hutchinsoniella Macracantha

Horseshoe Shrimp is the name for any member of the crustacean subclass Cephalocarida. They’re called “Horseshoe Shrimp” due to their horseshoe-like, curved body shape.

Most crustaceans have some form of eyes, but Horseshoe Shrimps are a very primitive group with no eyes. Additionally, they only have appendages in the thorax area.

This intriguing subclass of crustaceans is hermaphroditic, meaning that they carry reproductive organs of both sexes in the same body. Finally, they are suspension feeders, which means they can use the spines on their legs to catch food particles from the water.


Copepods

lots of zooplankton called copepods on a black background

Number of Species: 13,000
Notable Species:  Calanoida, Cyclopoida, Harpacticoida 

Copepods are a large and diverse group of tiny crustaceans belonging to the subclass Copepoda. They are one of the most abundant groups of animals on Earth, found in marine and freshwater habitats. 

Copepods vary in size and shape, but most are only a few millimeters long. They have segmented bodies with two pairs of antennae, and their legs are used for swimming. 

Copepods are essential grazers, consuming phytoplankton and zooplankton, and they are a valuable food source for many aquatic predators. 

Remipedes 

Number of Species: Approximately 20 
Notable Species: Lasionectes entrichoma, Speleonectes gironensis

Remipedes are an unusual and very primitive group of crustaceans. They belong to the subclass Remipedia, the only known crustaceans living exclusively in caves, feeding on bacteria and other tiny, sessile organisms.

Remipedes have a primitive body composed of a short head, a long trunk, and an abdominal region. They have three pairs of swimming appendages and lack eyes, antennae, or other sensory organs. They also don’t have any pigmentation.

Despite their primitive features, these free-swimming larvae have proven valuable for cave research.


Branchiopods

a branchiopod

Number of Species: 800 
Notable Species:  Fairy shrimp (Anostraca), brine shrimp (Artemis), clam shrimp (Laevicaudata)

Branchiopods are a group of small crustaceans in the subphylum Branchiopoda. They are most commonly found in freshwater habitats, but there are also some marine species. 

Branchiopods have an incredible range of shapes and sizes, from microscopic fairy shrimp to larger species like brine shrimp. Their colors vary greatly – many are dull or transparent, while others can be brightly colored.

Branchiopods have a unique feeding method – they filter out food particles from the water using their legs. This type of feeding is known as filter feeding, and it’s one of the most efficient ways for these tiny creatures to get the nutrients they need.


Mantis Shrimps

clown mantis shrimp

Number of Species: 450 
Notable Species: Peacock Mantis Shrimp, Squilla Mantis, Japanese Mantis Shrimp

Mantis shrimp are a type of crustacean belonging to the suborder Unipeltata. They have an elongated body, two claws on their front legs, and two eyes that can move independently from each other.

Mantis shrimp are found in tropical and subtropical waters around the world. Despite their small size, they are fierce predators and can catch prey up to five times their body length.

They have four larval stages; the most complex is the megalopa. This larval stage is particularly remarkable, as it has a shrimplike body and a large pair of eyes. 

Plus, they have impressive speed, as their club-like appendages can accelerate faster than a bullet.


Seed Shrimps

Number of Species: 70,000
Notable Species: Cypridopsis Vidua (Naked Seed Shrimp), Hemicytheria Ovata, Gigantocrypris Agassizii (Giant Seed Shrimp)

Seed shrimps are small crustaceans belonging to the class Ostracoda and characterized by their bivalve-like shell, composed of two hinged valves encasing their body.

Seed shrimps are found in many aquatic habitats, including freshwater, marine, and brackish environments. They play a critical ecological role as primary consumers and recyclers of organic matter in aquatic ecosystems. 

Their specific diet varies depending on the species, but generally, seed shrimps are filter feeders, using their specialized appendages to collect organic particles and plankton from the water column. Some species are detritivores, consuming dead plant and animal material.

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