Shellfish

Shellfish is a broad term that is used for various types of aquatic mollusks, crustaceans, and echinoderms that are used as food. The term shellfish is defined by including only those aquatic invertebrates that have a shell-like exoskeleton or a shell. These invertebrates are bivalves like clams and oysters, gastropods such as snails and abalone, lobsters, crabs, shrimps, and sea urchins, and some other animals are the shell-less cephalopods like squid and octopus. In addition to this, the word shellfish is primarily used as a term for the invertebrate species that live in marine water and the freshwater invertebrates that are edible such as river mussels and crayfish. These are sometimes grouped under marine species under the concept of "shellfish."

Shellfish provides certain important economic, culinary, and ecological values. They have been important as a food item in cuisines of many nations for thousands of years, and an important commercial industry has been grown up around them. Shellfish aquaculture enterprise is growing rapidly as that helps to provide a stable source of shellfish by not harming the wild populations. Ecologically, shellfish are vital in marine food chains along with this some filter-feeding forms are capable of purifying a great amount of water, and thus it is crucial to maintain the stability of the marine systems. And it was shellfish that were the "canaries of the sea" and alerted people to the danger of the disposal of human sewage.

Fish and Shellfish

Shellfish are the aquatic invertebrates that are used as food and typically these either have a hard exterior or an exoskeleton or they belong to a group of invertebrates that are characterized typically by such shells. Since almost all the shellfish contain a hard exterior or exoskeleton, the first part of the word is termed as “shell”. Whereas the second-word fragment is termed as “fish”, here the term is used in the archaic sense, to mean an animal that spends its whole life in the water. However, these invertebrate animals are not "fish" according to the modern sense of the word, and therefore the term finfish or fin fish is sometimes used to distinguish ordinary vertebrate fish from shellfish.

The word "shellfish" is used as both singular and plural, but the less common sometimes plural "shellfishes" is used while referring to various kinds of shellfish. The two most common groups of invertebrates that are associated with the term shellfish are the mollusks and crustaceans. Mollusks are commonly used as food that includes many of the species of mussels, clams, winkles, oysters, and scallops. Some decapod crustaceans are eaten commonly by various species of shrimp, prawns, lobsters, crayfish, and crabs.

Echinoderms are not as frequently eaten as compared to mollusks and crustaceans, but the roe of sea urchins is quite a popular one in many of the parts of the world. Whereas in Asia, sea cucumbers are gathered mostly as food items. These are sometimes also considered shellfish. Other edible mollusks are shell-less cephalopods such as octopus, squid, and cuttlefish, and certain terrestrial snails lacking a shell-like escargot, are sometimes considered to be shellfish.

Types of Shellfish Animal

As the name suggests, shellfish are animals that are capable of dwelling in the water and have a shell or shell-like exterior. They can be divided into two groups such as crustaceans and mollusks. 

Crustaceans include crab, crayfish, shrimp, and lobster, while certain scallops, clams, oysters, and mussels fall under the examples of mollusks. Most of the shellfish live in the saltwater, whereas the name refers to the species that are found in freshwater as well.

Shellfish is available all over the world in grocery stores and restaurants, but some of the regions are known for certain species. For instance, lobster is a popular food in the Northeast parts of the United States, while shrimp is used as a staple in dishes from the Southern part of the country. Most of the types of shellfish are eaten as baked, steamed, or fried. Some of the shellfish such as oysters and clams can be eaten raw or by cooking partially. Their flavor ranges from sweet to briny, from subtle to delicate depending on the type and the method of cooking.

Crustaceans Shellfish

Crustaceans form a large, diverse arthropod taxon that consists of animals such as crabs, prawns, lobsters, crayfish, krill, shrimps, woodlice, and barnacles. The crustacean group can be considered as a subphylum under the Mandibulata clade. Because of certain recent molecular studies, it is now well accepted that the crustacean group is treated as paraphyletic, and comprises all animals in the clade Pancrustacea other than hexapods. Some of the crustaceans shellfish are more closely related to the insect groups and the other hexapods than they are to certain other crustaceans.

The described species range is about 67,000, Stygotantulus stocki at the size of 0.1 mm, to the Japanese spider crab with a leg span of about 3.8 m and weight of 20 kg. Like other arthropods, crustaceans consist of an exoskeleton, which they molt to grow. These are distinguished from other groups of arthropods, such as insects like myriapods and chelicerates. These possess biramous limbs, and larval forms, the nauplius stage of the insect’s brachiopods and copepods.

Most of the crustaceans are free-living and aquatic animals, but some of these are terrestrial in nature, some of them are parasitic and some of them are sessile in nature. The group has an extensive fossil record while reaching back to the region of Cambrian, and it includes certain living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than about 7.9 million tons of crustaceans are produced per year by fishery or farming for the purpose of human consumption. Whereas most of them are shrimps and prawns. Krill and copepods are not fished as widely as compared to prawns and shrimps, but maybe the animals that are having the greatest biomass on the planet, and they form a vital part of the food chain. The scientific study of certain crustaceans is known as carcinology, and a scientist who works in carcinology is a carcinologist.

Crayfish Shellfish: Crayfish are freshwater crustaceans resembling small lobsters. Some parts of the United States are also known as crawdads, crawfish, mountain lobsters, freshwater lobsters, mudbugs, rock lobsters, or yabbies. Taxonomically, these are the members of the superfamilies such as Astacoidea and Parastacoidea. They breathe through specialized feather-like gills. Some of the species are found in brooks and streams where the freshwater is running, while other shellfish thrive in ditches, swamps, and paddy fields. Most crayfish cannot tolerate polluted water, although some species, such as Procambarus clarkii, are hardier. Crayfish can feed on animals and plants, either on living or decomposing, and detritus matter.

• Kingdom: Animalia

• Phylum: Arthropoda

• Subphylum: Crustacea

• Class: Malacostraca

• Order: Decapoda

• Suborder: Pleocyemata

• Infraorder: Astacidea

• Superfamily: Astacoidea

Mollusk Shellfish

Scallop Mollusk: Scallop is a common name that is primarily applicable to any one of the numerous species of saltwater clams or the marine bivalve mollusks in the family Pectinidae called the scallops. However, the scallop is the common name that is also sometimes applied to certain species in other closely related families within the superfamily Pectinoidea, which also includes the thorny oysters.

Scallops are a cosmopolitan family of bivalves that are found in almost all of the world's oceans, although never in freshwater. They are one of the very few groups of the mollusks or bivalves to be primarily free-living. Many of the species are capable of rapidly swimming to short distances and even these are migrating some distances across the ocean floor. A small minority of the species of scallops that live cemented to the rocky substrates as adults. While other members of the species get attached themselves to certain stationary or rooted objects such as seagrass at some point of time in their lives by means of a filament called a byssal thread, these are the filaments that they secrete. However the majority of the species live recumbent on sandy substrates, and when these can sense the presence of the predators such as a starfish. They may also attempt to escape from these predators by swimming swiftly but erratically through the water by using jet propulsion that was created by clapping their shells together. Scallops are found to have a well-developed nervous system, and unlike most of the other bivalves or mollusks, all scallops have a ring of numerous simple eyes that are situated around the edge of their mantles.

• Kingdom: Animalia

• Phylum: Mollusca

• Class: Bivalvia

• Order: Pectinida

• Superfamily: Pectinoidea

• Family: Pectinidae

Elephant Shellfish: The Pacific geoduck or gooey duck calm is a species of very large saltwater clam belonging to the family Hiatellidae. The geoduck is native to the regions of coastal waters of western Canada and the regions of the northwestern part of the United States. The shell of the clam ranges in length from 15 cm to over 20 cm, but the extremely long siphons can itself make the clam much longer than this, where the neck or siphons alone can be about one meter in length. The geoduck is the largest among the burrowing clams that is found in the world. It is also one of the longest-living animals found of any type, with a typical lifespan of about 140 years, where the oldest among them has been recorded at 168 years old.

The name geoduck is derived from a Lushootseed meaning "genitals" that is referring to the shape of the clam or "dig deep" which is the phrase of meaning, or sometimes both. It is sometimes known as a king clam or mud duck, or when translated literally from Chinese, an elephant-trunk clam. A group of geoducks is called a "bag". The Binomial name of the elephant shell or geoduck or gooey duck clam is Panopea generosa.

• Kingdom: Animalia

• Phylum: Mollusca

• Class: Bivalvia

• Subclass: Heterodonta

• Order: Adapedonta

• Family: Hiatellidae

• Genus: Panopea

• Species: P. generosa

Shellfish Animal Use in Various Cuisine

Some of the Archaeological finds have represented that humans have been making use of shellfish as a food item for thousands of years. In the present, shellfish dishes act as a feature of almost all the cuisines of the world, by serving as an important source of protein for many diets around the world, especially in countries with coastal areas.

In Japanese cuisine, chefs often make use of shellfish and their roe in different dishes. Sushi is a famous Japanese dish that features both raw and cooked shellfish. Sashimi primarily consists of very fresh raw seafood, sliced into thin pieces and served with only a dipping sauce, and a simple garnish such as shiso and shredded daikon radish.

In particular, lobster is a great delicacy in the United States, where the families in the Northeast region make them into the centerpiece of a clam bake, usually for certain special occasions. Lobsters are eaten on much of the regions of the East Coast the American lobster ranges from Newfoundland down to about the Carolinas but it is associated particularly with Maine.

Clams are mollusks that are served as food in most of the regions. Clamming is done both commercially and recreationally along the regions of the Northeast coastline of the United States. Various types of clams in New England are incorporated into the cuisine. Many types of clams can be used for clam chowder, a hard-shelled clam is also known as a chowder clam, is often used because the long cooking time softens its tougher meat.

Fish and Shellfish Health Benefits

May Aid Weight Loss: Shellfish are low in calories but it is high in lean proteins and healthy fats. These nutrients make them excellent foods to eat to the people who are trying to lose weight. Protein-rich foods make one feel full which may prevent eating an excess of calories. This helps people to lose weight or maintain it normally. Due to the presence of the high amount of omega-3 fatty acid content, consuming fish may lead to greater feelings of fullness where this aids in weight loss compared to other high-protein foods. One of the studies related to being overweight found that the adults who ate more omega-3 fatty acids on a diet that is calorie-restricted felt significantly fuller after meals than those who ate less omega-3 on the same diet.

May Promote Heart Health: Shellfishes are loaded with nutrients that may promote heart health, these nutrients include omega-3 fatty acids and vitamin B12. Several studies have linked that consuming omega-3 fatty acids from fish and shellfish can lower the risk of heart disease. This is because omega-3s have anti-inflammatory effects. Furthermore, inadequate intake of vitamin B12 has been linked to high blood levels which can control homocysteine, which is a protein that can increase the risk of heart disease. Therefore, consuming foods that are rich in vitamin B12 may protect one against heart disease.

Good for Your Brain: The same nutrients in shellfish that are good for your heart are also vital for brain health. In fact, several studies have identified in blood levels that inadequate levels of vitamin B12 and omega-3 content act as risk factors for issues that are related to brain development in children and with healthy brain function in adults. Some research also suggests that consumption of vitamin B12 and omega-3 fatty acids may enhance the activities to promote brain health. In one study that was conducted among 168 older adults with mild mental impairment, it is found that vitamin B is involved in slowing down brain issues. It happens in those who had higher blood levels of omega-3 fatty acids than those with lower levels.

Rich in Immune-Boosting Nutrients: Some types of shellfish are loaded with a nutrient that is immune-boosting zinc. This mineral is highly necessary for the development of the cells that can make up the body’s immune defense. It also acts as an antioxidant that protects against damage from inflammation. In one of the studies 62 healthy adults above the age of 90 are found to have zinc deficiency which was associated with decreased activity of certain immune cells. Regularly eating shellfish especially clams, lobster, oysters, mussels, and crab may improve the levels of zinc and overall immune function.

Fish and Shellfish Negative Aspects

Even though the consumption of shellfish is highly nutritious in nature, there may be some negative effects when it is consumed.

Heavy Metal Accumulation: In shellfish, the accumulation of heavy metals happens from their surrounding environments, these metals include mercury or cadmium. Humans are not capable of excreting heavy metals. Over time, a build-up of these heavy metals in the body can lead to damage of certain organs and other health issues. It is found that shellfish that are found in some areas may contain cadmium levels, these levels are twice more than it is recommended for consumption as a daily limit for humans. Shellfish may also contain mercury, but generally compared to the larger fish it is lesser in content. The FDA recommends adults to consume three to five ounces of fish that have low mercury content twice a week.

Foodborne Illness: Eating contaminated shellfish can lead to foodborne illness. In fact, mollusks like oysters, clams, scallops, and mussels accounted for about 45% of the cases that are related to sea foodborne illness in the US from the year 1973 to 2006. Food poisoning from certain shellfish can result from viruses, bacteria, or parasites that are acquired from their surrounding environments. Pathogens are found to flourish in raw shellfish and shellfishes that are chilled incorrectly. Therefore, storing and cooking shellfish in the proper way can be an effective way to prevent these kinds of foodborne illnesses.