Neptunus trituberculatus Miers, 1876
Portunus trituberculatus, the gazami crab, Japanese blue crab or horse crab, is the most widely fished species of crab in the world. It is found off the coasts of East Asia and is closely related to Portunus pelagicus.
P. trituberculatus is the world's most heavily fished crab species, with over 300,000 tonnes being caught annually, 98% of it off the coast of China. This is because it is considered highly nutritious, especially in regard to crab cream (roe).
The carapace may reach 15 centimetres (5.9 in) wide, and 7 cm (2.8 in) from front to back. P. trituberculatus may be distinguished from the closely related (and also widely fished) P. pelagicus by the number of broad teeth on the front of the carapace (3 in P. trituberculatus, 4 in P. pelagicus) and on the inner margin of the merus (4 in P. trituberculatus, 3 in P. pelagicus).
P. trituberculatus was first described by Edward J. Miers in 1876, under the name Neptunus trituberculatus. To better understand the species development, evolution and reproduction a reference genome has been sequenced, assembling to 1.0 Gb in size and anchoring to 50 chromosomes. And demonstrating it diverged from the Chinese mitten crab around 183.5 million years ago.