What are Chitons?

Chitons are mollusks in the class Polyplacophora, distinguished by their characteristic shells, which consist of eight overlapping plates. The creatures are widely found around the world, and fossil evidence suggests that they have been around for quite a long time. If you're interested in seeing some chitons for yourself, tidepooling is an excellent way to spot the unique animals, as they tend to favor the intertidal zone. Chitons may also be found in deeper water in some cases, but they exclusively marine, so they will never be found in freshwater.

Like other mollusks, a large part of a chiton's body is a large, muscular foot, surrounded by gills and a protective mantle. The animals pull themselves along rocks with their feet, scraping the rocks from algae and other forms of nutrition. A chiton is roughly oblong in shape, and the animals can be very hard to spot, since many have protective coloration which helps them blend in with the rocks. Others are radiant and very colorful; the creatures come in a wide range of colors and sizes.

In some regions of the world, chitons are known by other alternate names, such as loricates, coat of mail shells, and sea cradles. Some biologists also refer to them as polyplacaphorans, in a reference to their classification, which in turn refers to the multiple plates of their shell structures. When removed from their rocky substrate, chitons will curl up to protect their tender undersides until they bump into another rock to call home. This defense also makes the animals a less appealing source of potential food.

One unique variety of chiton, the gumboot chiton, is covered in a leathery layer of red skin. This layer obscures the shapes of the individual plates, and makes the animal difficult to differentiate from the colorful algae that line the rocky pools it prefers. Gumboot chitons can also get quite large, and often grow to sizes much larger than an average human hand. The animals once provided a source of food to Native Americans in the Northwest, thanks to their size.

Hundreds of individual species in a plethora of genera are classified as chitons. An assortment of marine animals prey on chitons, including starfish. Starfish pry the animals from the rock, using their assortment of tube feet to keep the chiton from curling up. Crabs, fish, and sometimes seagulls will eat chitons as well, in addition to sea anemones.

Chitons are marine mollusks known for their distinctive eight-plated shells and muscular, suction-like foot. They belong to the class Polyplacophora and are found in various ocean habitats, from intertidal zones to deep sea floors. These creatures have a unique sensory system with hundreds of tiny eyes embedded in their shells, providing them with rudimentary vision.

Chitons navigate using a combination of tactile and chemical cues sensed through their girdle and radula, a specialized feeding apparatus. Their shell eyes can detect changes in light, aiding in predator detection and navigation. Despite their simple nervous system, chitons effectively maneuver across rocky surfaces and can reorient themselves if flipped over.

Chitons primarily feed on algae and biofilms, which they scrape off rocks using their radula, a ribbon-like structure lined with teeth. Some species have specialized diets, including those that consume coralline algae or even other small invertebrates. Their feeding habits play a crucial role in maintaining the ecological balance of their marine environments.

Chitons reproduce by releasing sperm and eggs into the water column, where external fertilization occurs. Some species have more complex reproductive strategies, including internal fertilization and brooding of young. Once fertilized, the eggs develop into free-swimming larvae that eventually settle onto a hard surface and metamorphose into the adult form.

The lifespan of a chiton can vary widely depending on the species, with some living just a few years while others may live for over two decades. Factors such as habitat, predation, and environmental conditions can influence their longevity. Chitons are known for their resilience and ability to withstand harsh intertidal conditions.

Chitons play a vital role in their ecosystems as grazers that help control algal growth on rocky substrates. Their feeding activity promotes biodiversity by maintaining space for other organisms to colonize. Additionally, chitons serve as a food source for predators, including sea stars, fish, and birds, thus contributing to the marine food web.