January 11, 2011. 1  According to Education Next, teachers retire, on average, at around the age of 58. AARP reports that 33 percent of all beginning teachers leave the teaching profession within three years of beginning their careers, but the majority of teachers continue teaching and can reap retirement benefits later in life.
Deep-sea anglerfish, hatchetfish, and lantern fish are among the best-known luminescent fishes. In most such fishes, luminescence is produced intracellularly; the light is emitted by special cells called photocytes. The anatomical structure of the luminous organs of many fishes is similar to that of squids.
The cartilaginous fish, or Chondricthyes, include the sharks, rays, skates, and chimaeras. There are over eight hundred living species of sharks and rays, and about thirty species of chimaeras.Cartilaginous fish are true fish. They have fins and breathe with gills.harks, rays, and chimaeras or ratfishes make up the cartilaginous fishes (Chondrichthyes), one of the two major groups of fishes. The other major group is the ray-finned fishes (Actinopterygii). Unlike the more familiar rayfinned fishes, the cartilaginous fishes have skeletons composed entirely of cartilage.