Oysters are the epitome of gourmet eating. But these premium molluscs are more than a delicacy for connoisseurs. They sometimes hold hidden treasure and they team up to keep the water clean. These 5 facts just go to show that these shellfish have hidden talents!
Oysters are not only renowned as a delicacy but also as treasure chests. Theoretically, any oyster can form a pearl. We cannot say with absolute certainty how and why pearls form. But researchers believe that parasites entering the shell or other damage may create a cyst inside the shell. The material the shell is made of separates off at that spot, and a fluid is deposited around the irritant layer by layer until a pearl is formed. In cultured oyster beds, oysters take about 2 years to make each pearl, of which only around 10% can be used commercially for things like jewellery.
Oysters are environmental heroes. That’s because they filter water – up to 240 litres a day. Since they can’t set off in search of food, they eat whatever the tides carry their way. They consume nutrients and coat toxic substances in a mucus called pseudofeces. That keeps the water clean and helps reduce plankton. They don’t require any other food. All they need to make themselves at home on an oyster farm is a rack they can attach to. That makes them not only easy to care for but also particularly sustainable.
Oysters are only really happy in a community of their peers. The communes they form are called reefs, which offer both the oysters themselves as well as countless other species a home. Myriad other fish and invertebrates quickly join them and find shelter in the nooks and crannies in the reef. Within a few weeks, the biological diversity in these areas soars.
Around 90% of all oysters that are less than a year old are male. But about 80% of the ones over a year old are female. How can that be? They can change their gender, and they can do it several times during their 20-year lifetime. Depending on the nutrient content and temperature of the water, this may even happen more than once a year.
Pacific oysters are an especially popular variety with gourmets. But their road to superstar status in Europe and America was a long one. After starting out on the Pacific coast of Asia, they travelled to North America, Australia, Europe and New Zealand. In 1883, breeders took them from Portugal to the Netherlands to see if they could be introduced into the North Sea. With the European variety hit hard by oyster disease, the cultivators were hoping to find a more robust variety. Little did they know how successful their breeding plan would be: the molluscs have been multiplying massively since the 1960s. They have even been in the Wadden Sea since the late 1970s.