Cockle

Cockles are tiny creatures that fall into the same family as clams found in saltwater. They are very popular because they are edible. Their shells are heart-shaped and packed with soft, salty flesh, which is considered a delicacy in many countries across the world.

Another name for cockles is heart clams, and they form part of the Cardiidae family under the genus Cardium, known as bivalve mollusks. These creatures have two valves (two parts). In addition, cockles have over 250 species globally.

They occur globally and range in size from 0.4 to 6 inches, which is very similar to the size of the smooth giant cockle found off the coast of California.

They inhabit areas just below low tide levels. However, they can occur at depths of 1,500 feet, and several populations also live in the intertidal zone.

Three Amazing Cockle Facts

• Seafood sellers tend to call cockles by the wrong name. Various species of small and edible bivalves look similar to cockles but belong to other families. These species include Ark clams and Venus clams.
• Cockle populations are hard to document, but some species can reach densities of 10,000 individuals per square meter.
• Common cockles don’t really grow during winter, resulting in growth bands on their shells, which are used to determine their age.

Different Types of Cockle

While vast populations primarily occur in the Atlantic Ocean, they are found globally. There are multiple types of cockles found along the wet sands of the Atlantic coast, the four most popular being:

• The Great Heart Cockle
• The Florida Prickly Cockle
• The Atlantic Strawberry Cockle
• The Yellow Cockle

The Great Heart Cockle

The great heart cockle goes by many names, but the most well-known is Atlantic giant cockle. Enthusiasts love finding them because of their distinct heart shapes. In addition, they have a hidden heart that you can see when an intact cockle is turned on its side, and its opening is facing downwards.

Plentiful heart cockles are great assets to their ecosystems and help other marine animals. For example, they house tiny crabs inside their shells for protection from predators.

As their name suggests, great heart cockles are massive and measure up to 6 inches across, with 30 to 40 radial ribs from edge to edge. Yet, surprisingly, they are the same size as an adult human heart.

The Florida Prickly Cockle

As their name suggests, the Florida prickly cockle inhabits the coastal shores of southwestern Florida. Unlike other cockle species, their shells have a spiny appearance, hence the name prickly cockle.

These creatures are usually brown or salmon in color. However, shell-collecting enthusiasts hunt for unique albino shells, which are very rare.

Many people love collecting their shells because they are so small and beautiful. They only measure less than an inch from end to end, which compares to the size of a fingernail, and sometimes smaller.

The Atlantic Strawberry Cockle

Another cockle found along Florida’s coastline is the Atlantic strawberry cockle. While their populations are vast in this area, they are rare on the beaches.

They are narrower than other local species, but their most distinguishing feature is their reddish, rust-colored striping.

The Yellow Cockle

Yellow cockles are around 2 inches long when fully grown. This measurement is taken across the shell, away from the beak area. Like their name, they are yellow in color and almost circular in shape, with two valves equal in size.

The valve’s edges are serrated, and they interlock. In addition, their surface contains 20 to 40 radiating ribs. Some of these ribs (near the beak or umbonal area) are smooth, and others have small spines.

Their outer shell is yellowish-white, with pale brownish-red markings, while their inner surface is a beautiful, delicate yellow or white.

Classification and Scientific Name

The common cockle’s scientific name is Cerastoderma edule, and they belong to the order Cardiida. Another popular bivalve belongs to this order, the mussel. 1,389 species are members of this order in 203 genera and 7 families.

Interestingly, dead Cardiida members form shallow marine sediments. In addition, they have sexual reproduction.

Cockles form part of the family Cardiidae, which includes many bivalve mollusk species with an equivalve ribbed shell, distinct umbones, and a big foot that helps them crawl over the ocean floor. In addition, they have many-folded gills.

There are ten subfamilies. They include:

• Cardiinae
• Clinocardiinae
• Fraginae
• Laevicardiinae
• Lahiliinae
• Lymnocardiinae
• Orthocardiinae
• Protocardiinae
• Trachycardiinae
• Tridacninae

Appearance

Cockles live between two shells, hence the name bivalve. When holding one sideways, they have a distinct heart shape. In addition, the shells are ribbed. Their flesh inside the shell is gray, but this varies depending on the species. Cockles can grow up to 0.4 to 6 inches in size; on average, they weigh 0.88 ounces.

Behavior

While cockles look soft and supple, their bodies are actually full of muscle. Therefore, their bodies can be compared to the human tongue regarding strength.

They spend their days burrowing in the mud or sand or drifting in the surf. However, cockles are capable of much more.

Cockles use their tongue-like foot to kick, which helps them burrow into the sand. In addition, they often stick out their long foot to flip themselves over while relaxing on the surface of the sand.

While cockles can open and shut their shells, one of their most distinctive features is their unique ability to close their shells completely. This ability helps keep their squishy flesh from being preyed on by hungry predators.

Habitat

Cockles inhabit soft mud and fine sand in subtidal areas. However, they have a preference when it comes to the sand. Therefore, larger grain size is beneficial, and they are usually found in sand flats and eelgrass beds.

They can occur in depths of up to 65 feet in some areas, but prefer to inhabit shallow waters. In addition, they also occur in estuaries and can adapt to specific salinity increases.

Diet

The cockle’s diet is relatively simple. They enjoy consuming microscopic ocean organisms, which they filter through their gills.

Predators and Threats

Cockles are a significant target in their habitats. Many species of marine life like to prey on them. These creatures include:

• Seastars
• Bottom-feeders
• Shorebirds
• Seagulls
• Humans

Humans are cockles’ most significant threat because they are collected for commercial purposes. For example, cockles are sometimes used as a substitute for clams in recipes, but most seafood restaurants use true clams for dishes like baked clams.

They are usually served in their shells, which are the same as the shells most people collect on beaches. However, the ones served in eateries likely originate from a dedicated farm, so they aren’t as unique.

Their biggest threats in the wild are marine pollution caused by chemical waste discharge, the destruction of mangrove forests, cockle spats smuggled out of the country, and the use of destructive gear that damages the seabed.

Reproduction, Babies, and Lifespan

Depending on the species of cockle, their breeding seasons can last several months. Cockle eggs are fertilized when they are shed into the ocean along with sperm. Once the larvae hatch, they start to form and construct their shells and swim freely. Once their shells are fully-formed, they metamorphose at the bottom of the ocean or estuary.

Lifespan/Longevity

Cockles live quite long; their lifespan usually ranges from 5 to 10 years in the wild.

Population

Unfortunately, there is no definitive global population estimate for cockles, but regional surveys and production data are available for certain species and areas.

Ecosystem Roles

Cockles play a significant role in their ecosystem. Because they are filter feeders, they may accumulate bacteria, toxins, and viruses that plague their environment. When harvesting, this is a massive factor, and they should only be eaten if fished from unpolluted areas.

In addition, cockles can potentially warn marine biologists about the ecosystem’s health, which is a huge help.

As cockles are filter feeders, they provide an essential link in the food chain between the primary producers like phytoplankton and smaller predators like:

• Birds
• Crabs
• Rock lobsters

However, their most important role is their ability to filter water, which helps prevent phytoplankton blooms. This is essential because phytoplankton reduce oxygen availability for fish and thousands of other species.

What is the Difference Between Clams and Cockles?

The most significant distinction between a cockle and a clam is that the latter can be found in both freshwater and saltwater habitats, whereas cockles are limited to saltwater.

While the term ‘Cockle’ is used in a specific way, clam is a general name for several species. In addition, the general shape of their shells differs considerably. Cockles have a heart-shaped shell covered in ribs. In addition, their shells have very prominent markings, which makes it easy to distinguish them from clams.

On the other hand, clams come in multiple sizes and shapes, including circular, triangular, and elongated.

Cockles need to be cooked for consumption; however, people can eat clams raw. The best way to prepare cockles is by steaming them with butter and drizzling a lemon dressing over them.

Eating a cockle raw can cause severe food poisoning and several other health problems, such as Salmonella. However, people tend to prefer cockles to clams because they are more flavorsome.

Clams are bigger than cockles; however, both species belong to the clam family, so they also have many similarities.

Cockle Nutritional Facts

Cockles are a delicacy in many countries; however, they are not as popular as other seafood, like oysters and shrimp. This is a pity because they provide a substantial source of nutritional value.

Like many other bivalves, cockles have a chewy texture and salty-sweet taste. There is no limit to the magnitude of the cockle’s nutritional value. For example, their most significant dietary source is vitamin B12.

Just 3.5 ounces (100g) of cockles provides approximately 14-16mg of iron (100-200% of the recommended daily value) and 23.5-52mcg of vitamin B12 (about 588-2,000% of the recommended daily intake), making them an excellent source of these nutrients. Sacrificing 79  calories for all these nutrients seems like an easy choice.

Cockles are Low in Mercury

Unfortunately, many marine species that we consume are incredibly high in mercury. In fact, mercury is present in all seafood to a degree. However, it’s highest in larger animals like:

• Sharks
• Tuna
• Swordfish

If humans ingest too much mercury, it starts to dissolve the tissue and is often absorbed by the intestinal tissue. Absorbing large amounts of inorganic mercury causes bloody diarrhea. In addition, it can spread to other organ systems, affecting mental capacity, and resulting in memory loss, renal damage, and mood swings.

Recent studies confirm that cockles generally have low mercury levels, especially when compared to larger predatory fish such as sharks, tuna, and swordfish.

Cockles Provide Significant Amounts of Protein

There is an excellent source of protein in cockles; the amount of protein per calorie is highly impressive. In addition, cockles only contain 79 calories per 3.5-ounce serving, making the protein-per-calorie ratio astronomical!

Warning! Cockles are a Risk for Foodborne Illness if Eaten Raw

Like other shellfish species, one of the disadvantages of consuming cockles is that they can cause foodborne illnesses.

Cockles are filter feeders and can accumulate bacteria, leading to infections like vibriosis, hepatitis A, and salmonella. That’s why ensuring they are cooked properly before consumption is vital.

Before cooking any shellfish, adhere to the Washington State Department of Health’s guide on handling, cooking, and storing cockles, as well as other shellfish.

Generally, when cooking cockles, their internal temperature should reach 145°F (63°C), according to current FDA and USDA guidelines.