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Undersea secrets: How miraculous is the reproduction process of cancer crabs?
Cancer pagurus, also known as the edible brown crab, is found mainly in the North Sea and the North Atlantic Ocean, and may even inhabit the Mediterranean Sea. This crab is a sturdy, reddish-brown crab with a characteristic "pie crust" edge and black claw tips. A mature cancer crab eagle can reach up to 25 cm in width and weigh up to 3 kg. This crab is the most abundant in Western European crab fisheries, with annual catches exceeding 60,000 tonnes.
Appearance characteristics and living habits
The carapace of adult cancer crabs is reddish-brown, while that of juvenile crabs is purple-brown, sometimes with white spots. Their bodies are oval in shape, with nine circular ridges on the front edge, like the edge of a pie. The carapace length of male crabs is usually about 60 mm, while that of female crabs can reach 98 mm, and in extreme cases even up to 150 mm. This crab mainly hunts at night, mainly feeding on various types of mollusks and other crustaceans. The diversity of its diet makes it occupy an important position in the ecosystem of the seabed.
The Secret of Reproduction and the Life Cycle
Cancer crabs usually breed in the winter, with the male crabs on top of the female crabs, using their legs to form a "protective cage" to prevent other predators from intervening. Internal fertilization occurs during the molting process of the female crab, assisted by two abdominal appendages (genitalia). After mating, the female crab retreats into a pit on the seafloor and begins laying eggs, typically holding 250,000 to 3,000,000 fertilized eggs, which hatch eight months later.
The long-term protection of the eggs by the mother crab before they hatch shows the wisdom and precision of its reproductive process.
Newly hatched crabs are zoea, about 1 mm in size, which then develop into megalopa and finally juvenile crabs. In the first stage, the abdomen of the juvenile crab is fully developed, but as it grows it gradually shrinks in size and folds under the thorax. The juvenile crabs initially settle in the intertidal zone and move to deeper waters only when their body width reaches 60 to 70 mm.
Ecological Environment and Predators
Cancer crabs are widely distributed in the North Eastern Atlantic Ocean, from Norway to North Africa, and usually inhabit a seafloor mixed with rough, muddy and sandy materials. During the day, these crabs tend to hide in the sediment and come out to feed at night, preying on a variety of crustaceans and mollusks.
The main predator is the octopus, which will even attack fishermen in their crab traps.
While the reproduction process of cancer crabs is quite amazing, they are also vulnerable to all kinds of parasites and diseases, including various microorganisms and parasites. In commercial fishing, due to its economic value, cancer crab has become one of the most important commercial fishing species in Western Europe.
Importance of sustainable fishingThe fishing of cancer crabs is taken seriously, and countries have established some legal restrictions to protect the reproduction of these creatures. In particular, it is forbidden to capture female crabs that are "carrying eggs" and have high reproductive value in order to ensure future reproduction. However, specific fishing regulations vary due to the different growth rates of crab species in different places, and the minimum landing size (MLS) in some areas may be different.
Electromagnetic fields on the seafloor may have adverse effects on edible crabs, research suggests, showing the impact of human activities on marine ecosystems.
In the culinary world, crab's delicious meat is often used in a variety of dishes, such as soups and pies, making it a delicacy on the table. However, do we know enough about the ecology and reproductive habits of these unique creatures to develop more effective conservation measures in the future?
