1927, Japan introduced the first crayfish for use as feed for bullfrogs. It was introduced to China about two years later, and its earliest breeding ground was near Nanjing.
Lobster is shaped like a shrimp with a hard shell. The adult is about 5.6~ 1 1.9 cm long, and its overall color is red, reddish brown and pink. Dark red on the back, pink on both sides with orange or white spots.
Some crustaceans are almost black with wedge-shaped stripes on the back of their bellies. Larvae are all gray, sometimes with black ripples. Narrow pliers. The middle part of the carapace is not separated by a mesh gap, and there are obvious particles on the carapace.
Extended data
Crayfish can adapt to all kinds of polluted environment, thanks to its good detoxification mechanism, so the pollutant content in its body does not necessarily exceed the standard. Crayfish can transfer heavy metals into the shell, and then transfer toxins out of the body through constant molting, which is one of the reasons why it can tolerate heavy metal pollution.
Current research shows that heavy metals are mostly concentrated in gills, viscera and shells of shrimps that we don't like to eat. For people who eat shrimp meat, it is less likely to cause heavy metal poisoning.