Lesson 1
Cells with crowns
Many fish, like salmon, trout, and sharks, have a small pouch on the underside of the brain. It has a long name: the saccus vasculosus (say "SACK-us vas-kew-LOW-sus"). It is full of tiny blood vessels. You do not have one!
The pouch is lined with coronet cells. Coronet means "little crown". On top of each cell are many tiny hairs, and each hair ends in a little round ball. Together they look like a crown.
The crowns poke into the fluid that fills spaces inside the fish's brain.
Lesson 2
A season sensor
For more than 100 years, scientists were not sure what this pouch did. In 2013, scientists studying salmon found a clue. The pouch seems to help fish sense the seasons by noticing when days get longer or shorter.
Knowing the season helps fish get ready for big events, like when to lay eggs. Scientists are still learning how the coronet cells help.
Try thisScroll up to the 3D model and press Light up the crown to see the little balls on top of the cell.
Wow!You sense the seasons too! Long, light evenings in summer and early dark in winter help set your body clock.