[Brain of the cod (Gadus morhua morhua, Linné 1758) (Pisces, Paracanthopterygii). Qualitative and quantitative analysis of major subdivisions].

The Cod, Gadus morhua, is a North Atlantic fish of the family Gadidae which occurs at depths of 80 to 600 m (usually 150 to 200 m). It often occurs in shoals and tends to be migratory. It has a typical teleost brain except for the gadid feature of long olfactory tracts. Gadid fishes have a low level of encephalization (RIDET, 1982). The index of encephalization of the Cod is near the mean for the family. This index changes with season due to the change in body weight; it is lowest during the spawning season (which takes place in spring). Five subspecies of Gadus morhua are recognized. A comparison was made of the index of encephalization of the subspecies which is restricted to the White Sea, Gadus morhua maris albi, Derjugin 1920 and Gadus m. morhua, Linné 1758. The index of the White Sea form was significantly higher, thus supporting its recognition as subspecies. A volumetric analysis was made of the subdivisions of the Cod brain. It was found to have a large cerebellum, large medulla oblongata and a tendency to macrosmy, but a small telencephalon and tectum opticum (tendency to micropty). This is what would be expected from the environment and habits of this fish.