Portunus and sea crabs are divided into two parts: chest and abdomen. The head and chest cover is a prismatic head breastplate, blue-gray, with a pair of developed claw feet at the front end and four pairs of walking feet at the back end. Distributed in the northern and southern waters of China. Generally, from south to north, March to May and September to1October are the peak seasons for production, and the Liaodong Peninsula in Bohai Bay has more output from April to May.
Sea crabs inhabit soft mud, sand mud under rocks or aquatic plants with a water depth of 7 ~100 meters near the shore. A small number of small or medium-sized individuals can also be obtained on the low tide line in the intertidal zone. They usually crawl slowly on the seabed with the fingertips of the first three pairs of feet, swim with their swimming feet, or move forward sideways or backward sideways. When encountering an enemy, raise your big pincers upward to defend yourself or attack the opponent, or dig sand with the end of your swimming feet and dive into the bottom upright.
The body color of sea crabs varies with the surrounding environment. Individuals living in the sand bottom have a light gray-green head breastplate with a round white spot in the front gill area. Most of the claw feet are purple-red with white spots, and some or all of their ventral surfaces are white. The long joints and wrist joints of the first three pairs of feet are also white, the palms are blue-white, the fur is brown, the knuckles are purple-blue or purple-red, and the fourth pair of feet are green with white spots, with purple-blue fingers.
The head breastplate is spindle-shaped and slightly raised. There are three prominent verrucous bulges on the surface, 1 in the stomach area and 2 in the heart area. Its shape is like an ellipse, with sharp ends like weaving shuttles, so it has the name of sea crab. Each of the two front side edges has nine serrations, and the ninth serration is particularly long and extends to the left and right. Frontal margin has 4 small teeth. There are 1 pairs of rotatable compound eyes with handles on both sides of the forehead. have