Question: What varieties of food are included in the group Shellfish?
About the article "Seafood", section "Abstract".

Candidate passages:
Shellfish is a culinary and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms.
Although most kinds of shellfish are harvested from saltwater environments, some kinds are found only in freshwater.
In addition a few species of land crabs are eaten, for example "Cardisoma guanhumi" in the Caribbean.
Despite the name, shellfish are not a kind of fish, but are simply water-dwelling animals.
Many varieties of shellfish (crustaceans in particular) are actually closely related to insects and arachnids, making up one of the main classes of the phylum Arthropoda.
Cephalopods (squid, octopus, cuttlefish) and bivalves (clams, oysters) are molluscs, as are snails and slugs.
Familiar marine molluscs enjoyed as a food source by humans include many species of clams, mussels, oysters, winkles, and scallops.
Some crustaceans commonly eaten are shrimp, lobster, crayfish, and crabs.
Echinoderms are not as frequently harvested for food as molluscs and crustaceans, however sea urchin roe is quite popular in many parts of the world.
Most shellfish eat a diet composed primarily of phytoplankton and zooplankton.
Shellfish are among the most common food allergens. 
 in various cuisines.
Archaeological finds has shown that humans have been making use of shellfish as a food item for hundreds of thousands of years.
In the present, shellfish dishes are a feature of almost all the cuisines of the world, providing an important source of protein in many cuisines around the world, especially in the countries with coastal areas. 
Langoustines or Norway lobsters – "Nephrops norvegicus" – are roughly the size of a large crayfish and fished from silty bottom regions of the open Atlantic Ocean, and parts of the Mediterranean.
The fleshy tail of the Norway lobster is closer in both taste and texture to lobster and crayfish rather than prawn or shrimp.
They are often informally known as Dublin Bay prawns, though the term "prawn" can be confusing since it is sometimes used to describe several varieties of shellfish: the first group includes members of the lobster family such as scampi ("langoustine" in French and "cigala" in Spanish), while the second takes in large shrimp, particularly those that live in fresh water.
However, in terms of biological classification, lobsters like scampi are of a different family from prawns/shrimp.
The name is used loosely both in Italy and elsewhere to refer to other similar species, though some food labelling laws (in Britain, for example) define "scampi" as "Nephrops norvegicus". 
The most common food allergies in adults are shellfish and nuts.
The most common food allergies in children are shellfish, nuts, eggs, wheat, and soy.
A less common cause is exposure to certain bacteria, such as "Streptococcus" species or possibly "Helicobacter pylori". 
The ingredients consist of shellfish, meat, potatoes, milcao (a kind of potato dumpling), chapaleles, and vegetables (sometimes including also specific types of fish).
The varieties of shellfish vary but almejas (clams), cholgas (ribbed mussels) and picorocos (giant barnacles) are essential.
The quantities are not fixed; the idea is that there should be a little of everything.
Each layer of ingredients is covered with nalca (Chilean rhubarb) leaves, or in their absence, with fig leaves or white cabbage leaves.
All this is covered with wet sacks, and then with dirt and grass chunks, creating the effect of a giant pressure cooker in which the food cooks for approximately one hour.
Curanto can also be prepared in a large stew pot that is heated over a bonfire or grill or in a pressure cooker.
This "stewed curanto" is called "pulmay" in the central region of Chile.