Most chromosomes in a crustacean

Most chromosomes in a crustacean
Who
Astacus crayfishes, Pacifastacus crayfishes
What
376 total number
Where
Canada
When
1990s

The crustaceans with the most chromosomes are various crayfish species belonging to the genera Astacus and Pacifastacus, as some of these each possess 376 chromosomes (i.e., 188 pairs) per cell. These species include the signal crayfish (P. leniusculus), native to Canada and the USA, but introduced into many European species, where it has endangered the native European Astacus species by being a carrier of crayfish plague, to which the European species have no immunity.

Prior to the 1990s-publicized discovery that some crayfish species possess up to 376 chromosomes per cell, the crustacean species traditionally deemed to hold this record was the hermit crab (Pagurus ochotensis), which possesses 254 chromosomes (117 pairs) per cell.