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Crustaceans - Types & Characteristics

Crustaceans - a name that often evokes images of delicious seafood dinners, but there's so much more to these fascinating creatures. Part of the larger arthropod group, which includes insects and spiders, crustaceans are primarily aquatic beings that thrive both in the vast expanses of the oceans and the hidden recesses of freshwater bodies.

From the tiniest water fleas to the formidable giant crabs, they exhibit an astonishing range of sizes and adaptations, playing pivotal roles in aquatic ecosystems. Their ancient lineage, dating back to the Cambrian period (around 540 million years ago), speaks of a rich evolutionary journey, filled with stories of survival, diversification, and conquest of various aquatic habitats.

10 Characteristics of Crustaceans

  1. Exoskeleton: Crustaceans possess a hard exoskeleton, known as the carapace, which provides protection and structural support. This exoskeleton is periodically shed (molting) to allow for growth.

  2. Jointed Appendages: Like other arthropods, they have segmented, jointed limbs. The number and form of these appendages can vary widely among different crustaceans.

  3. Body Segmentation: Their bodies are typically divided into segments, with the head and thorax sometimes fused to form a cephalothorax, followed by the abdomen.

  4. Gills: They primarily respire using gills, which are efficient at extracting oxygen from water.

  5. Variety of Sizes: Crustaceans range in size from microscopic planktonic organisms, like copepods, to much larger creatures such as lobsters and Japanese spider crabs.

  6. Diverse Diet: Their diet ranges widely, from planktonic feeders to detritivores to predatory species.

  7. Sensory Antennae: Crustaceans typically have two pairs of antennae, which they use for sensory perception.

  8. Complex Life Cycles: Many crustaceans exhibit intricate life cycles, with different stages such as larvae, juveniles, and adults, each adapted to specific ecological niches.

  9. Compound Eyes: Many have compound eyes that provide a wide field of view, crucial for detecting predators or prey.

  10. Economical Importance: Several crustaceans, like shrimps, prawns, crabs, and lobsters, are of significant economic and dietary importance for humans worldwide.

Crustaceans - Crab on the beach

The 5 Types of Crustaceans

There are about 67,000 species of Crustaceans, which makes it a really big group. Crabs and shrimps immediately come to mind, but there actually are 5 main groups of Crustaceans. Let's take a closer look at them.

Crustaceans - Brine Shrimp

Branchiopoda (Brine Shrimp & Fairy Shrimp)

Primarily recognized for the familiar brine shrimp, Branchiopoda presents a fascinating subset of crustaceans. Often thriving in brackish environments, they can sometimes be observed in ephemeral pools that dry up seasonally.

Adapted for survival in such extreme conditions, their eggs can remain dormant for years before hatching. Their fairy-like swimming motions, especially apparent in fairy shrimps, make them an enchanting sight in freshwater habitats.

Crustaceans - Ostracod

Ostracods (Seed Shrimp)

At a mere glance, you might miss them. Ostracods, frequently dubbed “seed shrimp” due to their diminutive stature and appearance, are among the tiniest crustaceans. Though they barely reach 1mm in size, they’re encapsulated in a bivalve-like shell that offers protection from potential threats.

Despite their size, their presence is vital, playing a pivotal role in aquatic food chains and serving as a testament to the incredible diversity of the crustacean family.

Image via Wikimedia Commons


Venture deep into the saline groundwater realms, and you might come across the enigmatic Remipedia. These elongated crustaceans are not just blind but have developed an array of sensory adaptations to navigate their challenging habitats.

Their unique morphology, paired with their secluded environment, makes them one of the lesser-known yet intriguing members of the crustacean lineage.

Image via Wikimedia Commons

Crustaceans - Barnacles

Maxillopoda (Barnacles & Copepods)

A mosaic of forms and functionalities, the Maxillopoda class showcases the rich diversity within the crustacean group. From stationary barnacles, anchoring themselves on rocks and ship hulls, to the ever-vigilant copepods, which make up a significant fraction of the planktonic population in aquatic ecosystems, this group defies any single definition.

Their varied lifestyles and adaptations provide invaluable insights into the evolutionary pathways crustaceans have ventured.

Malacostraca (Crabs, Lobsters, & Shrimps)

When one thinks of crustaceans, it’s often the Malacostracans that first come to mind. Comprising the larger, more familiar members of the crustacean family, this group includes the likes of crabs, lobsters, and shrimps.

Their robust exoskeletons, often tinted in hues of blues, reds, and oranges, coupled with their complex behaviors, have not just captured human fascination but have also established them as vital economic commodities.

Whether it’s the formidable pinch of a crab, the graceful swim of a lobster, or the swift dart of a shrimp, Malacostracans are emblematic of the wonders the aquatic world has to offer.

Frequently Asked Questions About Custaceans

Crustaceans are a large group of arthropods that primarily live in aquatic environments. They include familiar creatures like crabs, lobsters, and shrimp, as well as many lesser-known species like barnacles and copepods.

Crustaceans, as arthropods, possess a hard exoskeleton, jointed limbs, and segmented bodies. Unlike fish, which have scales and breathe through gills located on their sides, crustaceans have their gills typically located beneath their bodies.

Crustaceans have a pigment called astaxanthin in their shells. When alive, this pigment is masked by other proteins. When cooked, these proteins break down, revealing the astaxanthin, which gives the cooked crustacean its characteristic red or pink hue.

Crustaceans grow by a process called molting. They shed their old, tight exoskeleton and produce a new, larger one. The new shell hardens over time, providing protection.

While many crustaceans are consumed as food worldwide, not all are edible. Some might have unpleasant flavors, toxins, or simply aren’t traditionally consumed.

Shrimp and prawns are similar, but they have differences in their body structure, especially in their gill structure and the way their bodies are segmented. The terms are often used interchangeably, especially in culinary contexts, but they belong to different suborders.

The understanding of pain in invertebrates, including crustaceans, is still a topic of scientific debate. Recent studies suggest they might have the capacity to experience pain, but it’s not fully understood in the same way as in vertebrates.

Though stationary, barnacles are active feeders. They possess feathery appendages known as cirri, which they extend into the water to capture tiny food particles.

Reproduction methods can vary among crustaceans. Many have separate sexes and engage in direct mating, while others might reproduce through parthenogenesis or even change sexes during their lifetimes.

Yes, while many crustaceans are marine, there are numerous freshwater species as well, like freshwater crabs, crayfish, and certain types of shrimp.

Learn More About Crustacean Species

Links to articles packed with surprising facts and knowledge to further learn about amazing species of Crustaceans, so you know what you are looking at on your next wildlife trip!

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