Large tabularhard scales (tabular ganoid scale) are lined up on the sides of the
body. There are five rows in total, two rows on each side (four rows on both
sides) and one row on the back. Many of the fish that prospered in the
Palaeozoic era (Devonian period and Carboniferous period) are thought to have had
tabular ganoid scales. In addition to the existing ancient fish sturgeons, coelacanths
and lungfish, which are called living fossils, have ganoid scales.
Stuergeon is called “butterfly shark” in Japanese because their scales look like
butterflies flying in a row.
Sturgeons are slimy like teleosts.
Supporting tissue
The spinal cord and notochord run
inside the spinal column, which ismade of cartilage. The spine
of the sturgeon is underdeveloped and is not able to fully function as a
supporting organ. Therefore, the notochord, which normally degenerates during
the developmental process, remains even in adulthood and functions as a major
supporting organ in the sturgeon.
In addition to the sturgeon, adult lamprey and hagfishhave a notochord. These fish also have underdeveloped vertebrae, and the notochord plays a major role as a supporting organ. This is a remnant of primitive vertebrates. The notochord of the sturgeon, which is over one meter in length, is one of the largest in existence.
Nervous system
Compared to the cerebellum of
teleosts, that of the sturgeonis smaller and poorer.
Considering that the cerebellum controls vision and movement, the size is
consistent with its slow movement.
