Crustaceans are a diverse group of invertebrates, characterized by their hard exoskeletons, segmented bodies, and jointed limbs. They belong to the subphylum Crustacea, part of the larger phylum Arthropoda, which also includes insects and spiders. While many crustaceans are aquatic, inhabiting various freshwater and marine environments, some species, like woodlice, have adapted to terrestrial life. Their remarkable diversity extends beyond habitat, encompassing a vast range of sizes, from microscopic water fleas to the giant Japanese spider crab. This wide array of forms and dwelling places hints at an equally varied set of dietary habits.
Crustaceans That Are Herbivores
Some crustaceans are herbivores, meaning their diet primarily consists of plant matter. These plant-eating crustaceans play a significant role as primary consumers in their ecosystems, helping to control the growth of primary producers like seagrasses and kelp. Their feeding habits contribute to a balanced environment by influencing food webs and nutrient cycling in aquatic systems.
Certain copepods are well-known examples of herbivores, feeding on phytoplankton, microscopic marine algae that form the base of many aquatic food webs. Fiddler crabs, commonly found in coastal areas, are also considered herbivores, consuming detritus derived from plant matter, such as decaying leaves and algae. Some amphipods and isopods, including those found in coastal habitats, graze on macroalgae and seagrasses. These crustaceans have developed adaptations to efficiently utilize plant material as their main nutrient source, even though plant matter can be low in nitrogen and high in difficult-to-digest compounds like cellulose and hemicellulose.
Crustaceans With Other Diets
While some crustaceans are herbivores, many others exhibit different dietary preferences, including being carnivores, omnivores, or detritivores. This wide range of feeding strategies allows them to thrive in various environments and occupy different niches within food webs.
Carnivores
Carnivorous crustaceans primarily prey on other animals. Mantis shrimp, for example, are known for their powerful claws used to strike and capture smaller fish and other invertebrates. Certain crabs, such as blue crabs, are also predatory, actively hunting and consuming shellfish and other marine organisms. These crustaceans often use their sense of smell to locate prey and their strong pincers to break through shells.
Omnivores
Many crustaceans are omnivores, meaning they consume a combination of both plant and animal matter. This dietary flexibility is common among species like lobsters, crayfish, and numerous types of crabs. They might eat algae, plankton, small fish, snails, or even other crustaceans. Their diet can also include organic matter left behind by larger predators.
Detritivores
Detritivores specialize in feeding on dead organic matter, known as detritus. This includes decomposing plant and animal parts, as well as feces. Some amphipods and isopods, like terrestrial woodlice, are examples of detritivores, breaking down decaying vegetation. In marine settings, certain benthic crustaceans, such as some crabs and lobsters, act as bottom-feeders, consuming organic debris that settles on the seabed. Filter-feeding crustaceans, like barnacles, also fall into this category, straining floating organic detritus and microscopic organisms from the water column.