The Big 5: Breaking down oyster types
The name of an oyster sometimes is a nod to their home waters (such as Wellfleet oysters from Wellfleet, Mass.) and sometimes is just a marketing whim, like Naked Cowboys named after the New York's underwear-wearing, guitar-playing Naked Cowboy. Though there are hundreds of different names for an oyster, there are just five distinct species. Here's a primer, along with some other the popular names you'll see them listed under in Chicago.
 Crassostrea gigas—Pacific or Japanese oysters (West Coast)
These include Kusshi from British Columbia, which are small and meaty, similar to a Kumamoto. Another oyster in this family is the Marin Miyagi (Tomales Bay, Calif.). We're pretty sure these are not named after the affable sensei from "The Karate Kid," but they are super-creamy.
 Crassostrea sikamea—Kumamoto oysters (West Coast)
There's an old maxim that you shouldn't eat oysters in months without an "r" in their name, a.k.a the summer. With modern transportation and refrigeration, that's no longer true; however, during the summer domestic oysters aren't always as pristine as they are in winter. Fruity and buttery Kumamotos tend to stay sweet and firm even through the summer.
 Crassostrea virginicas—Atlantic oysters (East Coast and Gulf of Mexico)
These probably are the most ubiquitous oysters and include some of the most familiar names, such as Malpeque, Wellfleets, Blue Points and Beausoleils. These oysters generally are large, briny and metallic in flavor. They grow from New Brunswick, Canada, to Virginia, and also in the Gulf of Mexico—the further south, the bigger they get. Beausoleils are small, cold-water oysters, often with a nutty note that's great for novices. Small, sweet Apalachicolas from the Florida panhandle have appeared on local menus in recent years. Shigokus also are common; though the name sounds similar to "Chicago," these fatty, briny, deep-cupped oysters are from Washington state.
 Ostrea edulis—European flats (East and West coasts)
These are the beloved Belon oysters. You won't see European Belons in Chicago, but you may see Maine Belons or Maine Flats, which are ostrea edulis grown on America's Atlantic coast. Though you likely won't see them in on local menus, Westcott Bay Flats are ostrea edulis from Washington state's Puget Sound. These oysters are meaty, big and have a rich, mouth-coating flavor.
 Ostrea lurida—Olympia oysters (West Coast)
Tiny, almost thumb-sized Olympias are sweet and have a celery-like finish. These oysters are now rare and are thought to be disappearing because of ocean acidification and predatory snails.
Oysters for vegans?
Oysters subsist on plankton and filter and improve the waters in which they grow, so they are considered a very sustainable food. Because oysters also lack a central nervous system, scientists theorize that, like plants, they may not feel any pain. Some ethicists have even suggested that oysters are OK for vegans to consume.