The season of spawning and hatching of Chinese mitten crabs is also the season when other species of crabs lay their eggs in the estuary and hatch. Therefore, natural crab seedlings are often prone to miscellaneous with other species, among which Tianjin thick crabs (commonly known as alfalfa) are the most common, and their number is also the most. In some years, the number of crab crabs in Tianjin is even higher than that of Chinese mitten crabs. The main difference between them is:
(1) Different seasons
Tianjin crab crabs appeared 7 to 15 days earlier than the Chinese mitten crabs.
(2) Different individuals
Eriocheir sinensis crab crab seedlings are large in size and heavy in weight, whereas the crabs in Tianjin are small in size and light in weight. It has been determined that the weight of each Chinese eel crab crab seedling is 4.10.58 milligrams, and that of Tianjin thick crab crab seedling is only 2.730.28 milligrams each. The former is 1/3 heavier than the latter.
(3) Different shades of color
During the same period (4 to 5 days old) of crabs, the Chinese mitten crabs had darker body color and the head larvae were light green-yellow; while the thick crabs and crabs in Tianjin were pale and translucent.
(4) Morphological differences
The forehead teeth of the Chinese mitten crab crabs were sharp on both sides, and their edges and corners were distinct, and the depths were deep in the middle. However, the frontal teeth of the thick crab crabs in Tianjin were bluntly rounded on both sides and had no edges and corners. The frontal plane was flat with a concave in the middle. There were 4 serrations on the inside of the second and third pairs of stepped toe joints (the most distal section) of the Chinese mitten crab crab, and the toe knots of all the stepped feet of the thick crab crab showed no jaggies. Significant difference.
(5) Differences in ecological habits after the period crabs
After rearing in earthen ponds, the thick-eyed larvae of T. tianjinensis are perched on the bank after the period of development. They burrow on the surface of the water and live in burrowing habitats. They are small in size, dark in color, and gray-black in color; Crab bigeye larvae metamorphosis for the first phase of crabs, inhabits in the pool of aquatic grasses, their larger individuals, body color is yellow. Generally, the Chinese mitten crab does not dig a hole before stage III crabs and lives in seclusion.
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