Overseas
Bivalve Molluscs or Lamellibranchs are mussels, clams, tellines and oysters; as the word itself suggests, they have a shell made up of two hinged valves and lamellar gills. The body of these aquatic molluscs, mostly marine, is always enclosed inside the shell; it is very compressed and not differentiated. The shell, always present, is secreted by the mantle and has a shiny, iridescent inner layer called nacre (mother-of-pearl).
Bivalves are part of the benthos: they live buried in sand or mud and constantly filter water, feeding mainly on plankton. They are prey for many fish, echinoderms (starfish) and other molluscs (cephalopods). They are also very important for human nutrition: in addition to harvesting them, humans have learned to farm them. Beyond their very tasty flesh, they are used for their shells and, in the case of oysters, for pearls.
Bivalves, commonly called seafood and also eaten raw, being filter feeders can accumulate pollutants, bacteria and viruses that are very dangerous to human health; just think that mussels can be a vehicle for typhoid, cholera, viral hepatitis, etc. For this reason, we recommend consuming them only when you are certain of their origin and, preferably, cooked.
Mussels, Mytilus galloprovincialis
Mussels (Mytilus galloprovincialis), are marine, equal-valved bivalve molluscs.
Distribution and habitat
The mussel lives anchored to rocks by means of the “byssus,” on seabeds that can be very shallow throughout the Mediterranean, the eastern Atlantic and Morocco. Because of its adaptive capacity and rapid spread, it is considered an invasive species in many regions of the world such as Japan and Australia, and it has been included in the list of the 100 most harmful invasive species.
Description
The shell is composed mainly of calcium carbonate; the two valves are perfectly identical, black in colour, with growth lines; the inside is smooth and pearly. The two valves are hinged by three/four small teeth.
Harvesting
Today, the mussels found on the market are farmed, sold in specific plastic nets, and must be marked with a label; we strongly discourage buying loose mussels without netting and a label. From a nutritional point of view, mussels do not have a high caloric contribution (70 kcal per 100 g). They are rich in minerals (selenium, iron, iodine) and vitamins (E group and B group), contain a good percentage of omega-3 fatty acids, and a not negligible cholesterol content (like all bivalves).
Oyster, Ostrea
The oyster (Ostrea) is a marine bivalve mollusc, with a shell formed by two unequal valves covered with wavy lamellae.
Distribution and habitat
The oyster is a bivalve widely distributed in all European seas and in tropical seas where it is farmed for pearl production. It lives at low depths on hard bottoms, anchored to rocks or other solid bodies. Ostrea edulis, the species commonly used for the table, lives from the surface down to about 50 metres in depth.
Description
A mollusc that can also reach large sizes, it lives anchored to rocks by one of the two valves, generally the left, which is perfectly welded to the substrate. The shell is rounded and has lamellae that give it its classic appearance, and it can measure up to 12 cm.
Harvesting
For oysters too, we can state that those on the market are farmed; we speak of oyster farming. The oyster, characterised by a very low fat content (about 2%), offers an important share of high-quality proteins and all four fundamental vitamins (A, B, C, D). It is also a good source of phosphorus, calcium and magnesium, but it is the abundance of zinc and iron that makes this mollusc particularly interesting in combating anaemia.
Verace clam, Tapes decussata
The “verace” clam (Tapes decussata), commonly called clam, is a marine, equal-valved bivalve mollusc.
Distribution and habitat
The verace clam is a Mediterranean species, found from a few metres down to not very high depths, up to a maximum of about 20 metres. It lives on soft coastal and lagoon bottoms, and on muddy bottoms covered with vegetation. In general, clams are gregarious.
Description
The shell of the clam has a very variable colour, from white with some dark spots to blackish in the case of individuals harvested in poorly oxygenated areas. It is oval or slightly angled in shape, with an outer surface marked by concentric and radial lines; the inside is smooth. The clam has two siphons, inhalant and exhalant, completely separate. Sizes range from 4 to 7 centimetres. According to Italian law, the Philippine clam (Tapes philippinarum), an Indo-Pacific mollusc introduced into the Adriatic in the 1980s for commercial reasons, is also considered “verace.” The latter has a shell with an outer surface characterised by more marked growth striae and radial elements, fused siphons, and much shorter growth times than the Mediterranean clam (2 years instead of 3 years). The “Philippine” clam, in addition to growing and reproducing more quickly, is also more resistant than the Mediterranean one and, not to be underestimated, it can reproduce in hatcheries. In a few years, the “verace” clam was replaced by the Indo-Pacific clam both at sea and on our tables; the “verace” clam has almost disappeared in the Mediterranean Sea and survives only in a few locations.
Harvesting
Fishing is carried out with specific boats and tools that dredge the bottom, such as the “rasca.” Clams are a food rich in vitamins and mineral salts: vitamins of group A, useful for skin, hair and vision, and against free radicals and cellular ageing; group C, for strengthening the immune system; and B vitamins; as well as minerals such as potassium, magnesium, calcium, iron and sodium.
Subscribe to the Pesceinrete weekly newsletter for exclusive news and insights from the seafood industry.
Commenti 1