Oysters and mussels are seafood. At first glance, a layman will find no difference between clams, mussels, oysters or scallops; but technically all are different. All of these belong to the mollusk family i.e. they are invertebrate having one, two or more shells that completely or partially cover their soft, un-segmented body. Other organisms from this family are octopuses, snails, squids, etc. Oysters, clams, mussels are reared and harvested for food and pearls. The difference between oysters and mussels can be observed in the following ways:

Oysters

Oyster refers to a few groups of marine and brackish water bivalves. They are bivalve mollusks of the super-family Ostreidae.

Mussels

Mussel is technically used for many types of bivalves living in both freshwater and saltwater ecosystems. Mussel is an edible bivalve of the family: Mytilidae. Some species of mussel prefer to live around deep-sea hydro-dermal vents. Majority of the edible species live attached to the substrates in the inter-tidal zone.

Oysters Vs Mussels

Shell shape

Oysters have an irregularly shaped shell. The shell is highly calcified, and two shells are joined by a small hinge. Oyster shells are hard, rough, dull and covered in barnacles. These hard shells are substrates for several sea grass as well as sea animals like sea anemone, mussels, barnacles, etc.

Mussels have a long pair of shells that are brown or purplish black in colour. The shells are more oblong than oyster shells. The inside is silver or greyish. A muscular foot is clear out of all the organs. They clump together onto the substrates to remain well attached. This helps them to protect from being thrashed away by the powerful waves.

Size

Oysters can be huge. The largest oyster discovered was around 15 inches.

Mussels are typically the smallest of the mollusks. They come in a wide range of colours.

Habitat

Oysters live in saltwater and have a more calcified, irregular shaped shell.

Mussels live in symbiotic colonies. They help each other to survive. Mussels in the middle are helped by others to save them from dehydration during a low tide.

Fertilization process

Oysters can produce eggs and sperms inside the same individual. They multiply rapidly.  Millions of self-fertilized eggs develop into larvae in six hours only. They find a permanent substrate within a couple of weeks and mature in a year. The oysters hatch out of the eggs and live temporarily attached to a host during their glochidia stage. They are mobile also. They move to the oyster bed or oyster reef which is a safe haven for all oysters. Oyster beds are a place of stabilized ecosystems as they provide a great habitat for many types of plants and animals.

Mussels can be male or female. Their fertilization takes place externally, the eggs convert into larvae which attach to the gills or fins as temporary parasites. These are known as glochidia. They attach to a specific fish species as their hosts. After two weeks of glochidia stage, mussels start their individual lifestyle. Now, they are ready for consumption.

Uses

Oysters are filter-feeders. They have a special ‘siphon’ in their body that helps to take water in and filter it. They filter the pollutants like nitrogen-compounds, suspended particles and phytoplankton from water. An individual oyster filters about five litres of water per hour. Oysters are very significant for humans. They are home to the precious pearls that are used to make ornaments and jewellery.

Mussels are a great source of proteins. Mussels are home to pearls as they are a part of mollusk family.

Varieties

Some edible varieties of oysters are: Ostrea angasi, Ostria edulis, dredge oyster, Auckland oyster, rock oyster, Pacific oyster, Portugese oyster, mangrove oyster etc

Some edible mussel species are: Californie mussels, Mediterranean mussels, Mytilus coruscus, Perna canalicula, Perna perna, Perna viridis, etc.

Conclusion

Mussels and oysters are fresh or saltwater inhabitants. Mussel shells are hard, oblonged and shiny, while oyster shells are oval and rough. Unlike clams and scallops, mussels and oysters are rooted into their substrates. Mussels have feet too, but they prefer to be rooted. They are sessile. Despite all the differences, all mollusks are home to unique pearls and are edible mollusks are a treat for food enthusiasts.