About Chasmagnathus convexus (De Haan, 1835)
Chasmagnathus convexus is a common mud-flat crab belonging to the family Varunidae, and it is endemic to East Asia. In Japan, this species is commonly known as hamagani. Two distinct color forms exist for this crab: one is olive green, and the other is purple. Researchers believe that differences in diet cause this color variation between the two forms. Compared to closely related crabs, C. convexus is a large species, with a carapace width that can reach between 4.5 and 5 centimetres, or 1.8 to 2.0 inches. This crab is predominantly nocturnal.
