Chiton

Chitons belong to the class Polyplacophora, which comprises marine mollusks. This complex word is Latin for “many plates.”

The class consists mainly of chitons, with 8 plates or valves that overlap on their elongated, slender shells. Most of these curious creatures live in the intertidal zone and measure between 0.3 and 12 inches in length.

Chitons use their shells to protect their fragile organs underneath. Under the shell plates, their mantles are bordered by a skirt or girdle. In addition, they can have spines or hairs.

While the shell mainly acts as a shield for the chiton, it is also flexible, and its overlapping design enables it to flex in an upward motion, which is how it moves. In addition, chitons can curl into balls and do this when they need protection.

Three Amazing Chiton Facts

• Chitons are very adaptable and can live in both cold and tropical waters. Many inhabit tidal zones and can tolerate air exposure for several minutes. Others prefer the deep ocean and can survive 20,000 feet under the sea’s surface.
• They never stray far from home but exhibit homing techniques, which means they venture away from their habitat to feed and return to the same spot.
• These strange creatures are edible, and people eat them all over the world, but most commonly in the Caribbean islands, Aruba, Barbados, Bermuda, Tobago, and Trinidad. In addition, they are also consumed in North and South America and the Philippines.

Classification and Scientific Name

The chiton belongs to the class Polyplacophora; however, until recently, it was known as Amphineura. These curious creatures are also known as:

• Polyplacophorans
• Sea Cradles
• Coat-of-mail shells
• Loricates

The most distinguishing feature of this class is a flattened, oval-shaped, wide ventral foot, with seven or eight dorsal shell plates overlapping each other. This allows the animal to bend or curl, molding itself into a rock, and avoiding wave dislodgement.

Chitons belong to the Phylum Mollusca, which is the largest aquatic phylum in the world, consisting of 23% of all marine organisms. In addition, multiple mollusk species live in freshwater and terrestrial habitats.

Mollusks are a highly diverse group of animals, not just in anatomical structure and size but in habitat and behavior as well. Typically, the phylum is divided into 7 or 8 taxonomic classes; unfortunately, two of those are extinct.

Appearance

Chitons are closely related to snails, oysters, and mussels because of their shared phylum. However, one of their most distinctive characteristics is that these unique creatures have 8 shell plates on their bodies, slightly overlapping each other. These overlapping plates help the chiton to convert into a ball-like shape when it feels threatened or to avoid being displaced by a wave.

Their shells are encompassed by a girdle, also known as a skirt, whose purpose is to cover the plates to different extents. In fact, they are named after these distinctive plates; Polyplacophora means “many plates” in Latin.

The chiton’s body is covered in shell plates of various lengths and comes in an array of bright colors. Chiton’s mouths are located on the underside of their shell body. These strange creatures only have one foot, which they use for hanging onto rocks. In addition, they have a radula, a tiny teeth-like structure used to scrape rocks.

Behavior

Chitons will hide under rocks during the day because they are nocturnal animals that feed at night. They prefer to inhabit intertidal zones and cling to hard surfaces like rock crevices or under rocks.

Certain species occur in high intertidal zones and can survive exposure to light and air for several hours. However, other species live subtidally or in deep water as low as 20,000 feet under the surface.

Habitat

The chiton’s preferred habitat is a rocky area extending from exposed beaches and tidal pools up to 365 feet. Generally, most species prefer intertidal areas compared to subtidal zones.

Diet

Chitons have species that are both carnivorous and herbivorous that eat plankton. In addition, they scrape algae off the rocks and eat tiny invertebrates and fish abundant in their marine habitat.

Predators and Threats

The chiton has numerous predators that include vertebrates and invertebrates, such as:

• Sea Stars
• Crabs
• Sea Snails
• Birds
• Fish

However, the main predator of the green chiton is a bird called an oystercatcher. These crafty birds are native to New Zealand and prey on chiton from rocky shores. They have learned a technique where they strike sharply at an angle on the chiton’s shell plates.

If this action does not dislodge them, the birds start to apply pressure on the margin between the rock surface and the chiton’s foot. Then, they use a scissor-like motion to pry them from their grip. They can do this as long as it takes until, finally, the organism is separated from the rocks. In addition, the chiton’s valves are taken off and eaten in one large piece.

While they have no known threats, the chitons may be susceptible to climate change and the temperature increase of the ocean, much like other marine life.

One chiton species, the Hanleyella henrici, is listed as Endangered on IUCN’s Redlist.

Reproduction, Babies, and Lifespan

Very little is known about the chiton’s mating habits, but they have been observed spawning. Researchers have noted that they wait for a full moon to conduct spawning. However, this also depends on the conditions at the time, and if they are not desirable, or the sea is too rough, they will hold off on spawning until the next full moon.

Typically, chitons have separate sexes, and their sperm and eggs are released through a gonad located at the posterior end of the foot. Their larval distribution is not excellent because they don’t have a free-swimming larval stage.

The eggs are released through the anus and flow with the currents into plankton, where they hatch two days later.

Lifespan/Longevity

Chiton’s lifespans vary from species to species, but generally, they live between 1 and 20 years of age.

Population

Unfortunately, there is no recorded data about the population size of the chiton. Too many species are distributed widely across several oceans, so it would be impossible to determine their exact numbers.

Animals Similar to the Chiton

Chitons have been around for nearly 500 million years, and they are the only known living mollusk with living tissue connected within the outermost layer of their shells. However, there are a few species that share similar characteristics, and they include:

Sea snails

The sea snail has a fragile, supple body but uses a shell for protection. Most of their shells are spiraled; however, some species of sea snails, called impetus, have conical shells. This makes it hard for certain predators to prey on them.

Sea snails are mainly considered herbivores, and their primary food source is sea plants. However, some species are omnivores, like the Cone snail.

These slimy mollusks do not have teeth; instead, their mouths contain a hard ribbon. They use this ribbon to tear and grind their food.

Sea snails get around by moving their foot, which is a muscular organ similar to the human tongue, beneath their bodies. This motion involves a ripping movement and leaves a trail of mucus in its wake.

In addition, sea snails have gills that are located in the cavity of their mantles, which they use for breathing. So many species of sea snails are spread diversely through habitats across the globe, ranging from the deep Arctic to the equatorial regions of the Antarctic oceans! In addition, they inhabit vast areas, from coastlines to the deepest ocean trenches.

Mussels

Mussels are tiny creatures that inhabit either fresh or saltwater. In addition, many commercial farms cultivate them for human consumption. These bivalves are bluish-black in color with a nacreous layer within the shell’s outer walls.

Mussels’ diet consists of algae and plankton. In addition, they stick to rocks through byssal threads, also known as beards. This thread is made from a slimy protein, which is high in iron and very nutritious for humans. In fact, scientists are working on a commercial venture involving a nutrient-rich product made from the byssal thread.

Mussels inhabit intertidal zones of oceans all over the world, including zones in tropical regions; however, they are more abundant in temperate zones. In addition, some species of mussels prefer to live in marine marshes or bays. They are often seen completely covering rock formations and can stick to them, even under massive pressure from monstrous waves.

Mussels also occur near hydrothermal vents, like the South African species that dig into the ground and cover themselves with sand. Only two of their tubes protrude from the sand, which they use for water, food, and to excrete waste.

Then there are freshwater mussels that desperately need clear and cold water. Freshwater mussels rely on calcium to strengthen their shells, so they inhabit water bodies with high amounts of mineral content.

Oysters

The oyster is a general name used for many different families of saltwater mollusks, often found in brackish, marine waters worldwide. As a result, oysters play an essential role in water ecosystems around the globe. In addition, oysters are considered an aphrodisiac in many cultures around the world and can be cooked or eaten raw with a squeeze of fresh lemon juice.

Five of the best oysters to eat are:

• Kumamoto Oysters
• Stellar Bay Oysters
• Grassy Bay Oysters
• Miyagi Oysters
• Malepeque Oysters

European flat oysters also go by the names true oysters, eastern oysters, Pacific oysters, Lympia oysters, and Sydney rock oysters. Pearl oysters are members of the feathered oyster family and occur in both freshwater and saltwater. However, they are not the only oysters that are edible or produce a pearl; these species include:

• Thorny oysters
• Pilgrim oysters (also called the scallop shell of St. James)
• Saddle oysters
• Dimydarian oysters

While some oyster species are listed as Least Concern on the IUCN Red List, certain oyster ecosystems, such as the European native oyster reef, have been classified as ‘Collapsed’ by the IUCN Red List of Ecosystems, reflecting significant regional declines.

American oysters are the most well-known and heavily consumed oyster in the world, and they inhabit the Atlantic Ocean from Canada to Argentina.

Another popular bivalve is the Pacific oyster (Crassostrea gigas), and they are known to inhabit oyster reefs alongside mussels and barnacles. To breathe and feed, oysters need to filter large amounts of water.

Squids

Squids occupy regions of every ocean in the world because there are over 300 different species. The largest member of this family is the Giant squid, which inhabits large sections of the Indian and North Atlantic Oceans. They can grow to lengths of 33 to 43 feet!

Squids can live at depths of 1000 feet below the surface because their bodies are well equipped to deal with the icy waters, which many species find uninhabitable. They are predatory animals, and each has a variety of prey, including:

• Krill
• Fish
• Other squids

Certain squid species have this unique ability to light up their surroundings with bioluminescent organs, which helps them navigate their way through deep, dark waters.

Squids are often confused with octopuses, but they have characteristics that help differentiate between them. For example, in addition to having eight arms, the squid also has two tentacles, while the octopus only has eight arms.

Squids have sharp beaks that are really tough compared to the rest of their limp bodies. They use their beaks to chop up prey into tiny pieces in order to swallow.