Oysters are mollusks mentioned in the How to Train Your Dragon Book series.
The term 'oyster' may actually refer to members of several families of bivalves (Class Bivalva) rather than a specific grouping. Examples are the Family Ostreidae or True Oysters, and Family Pteriidae or Feathered Oysters. Though all oysters and other bivalves have the potential to produce pearls, members of the feathered oyster family are most known commercially as 'pearl oysters'.
Generally, oysters consist of two asymmetrical shells, or valves. Oysters are filter feeders, pulling in water across their gills, where debris and creatures such as Plankton become trapped and digested. Adult oysters are sessile, adhering to a substrate and remaining immobile.
Oysters are valuable as a food source, as well as pearl production. In the Book series, oysters are also mentioned as an item of barter. Particularly the in-universe book How to Train Your Dragon costs 1 smallish chicken and 20 oysters. In the Book series, oysters may also be referenced as an insult.
Oysters are mentioned as part of the price for the book How to Train Your Dragon, by Professor Yobbish.
Hiccup is also seen harvesting oysters while waiting for Toothless to catch fish.
|“||Hiccup had gotten bored and was looking for oysters when Toothless came bursting triumphantly out of the sea carrying a small mackerel.||”|
|— Book 1|
Toothless' toothless mouth is described as having "hard little gums could slice through the shell of an oyster and crush the claws of a crab". This implies that Dragons also enjoy eating oysters, along with Vikings.
Also seen in How to Be a Pirate, Hiccup tries to get Toothless out of the house to practice sniffing for treasure. He uses food to tempt him, including a mackerel "as well a small haddock pie and three or four oysters."
|“||Snotlout's granny is a yellow-bellied decrepit old oyster, Snotlout's granny is a barking mad old walrus-head ...||”|
|— Gobber in Book 2|
Baggybum the Beerbelly uses the word oyster in an exclamation.
|“||Now hang on an oyster-catching minute||”|
|“||Gorgeous silver cups with seahorses galloping delicately around them and golden necklaces as plump as oysters and swords as sharp as a conger's tooth with octopus tentacles winding themselves around the hilt.||”|
|— Book 2|
The map at the front of this book introduces the island of Bashem. Its Northeast coast is called the 'Oyster Beds', presumably because there are plentiful oysters here.
Oysters are also mentioned when Hiccup and Toothless argue about Toothless' disobedience and selfish desires.
|— Hiccup and Toothless speaking in Dragonese|
Oysters are seen on the breakfast table in the Haddock household when Hiccup tells Stoick about the Roman's 'Fiendishly Clever Plan' to start conflict between the Hooligans and the Bog-Burglars.