* It's a tooth, not a tusk: The narwhal's "tusk" is actually a left canine tooth that grows out of the upper jaw.
* Spiral growth: This tooth grows in a long, spiral shape, unlike normal teeth.
* Growth process: It begins as a regular tooth bud, but then starts growing outwards, lengthening throughout the narwhal's life. The growth is continuous and influenced by the narwhal's age, genetics, and environmental factors.
* No enamel: The tooth is covered in dentin, not enamel like regular teeth.
* Purpose: The exact purpose of the tusk is still debated, but theories include:
* Sensory organ: It might detect changes in water pressure, temperature, and salinity.
* Fighting: Used for competition among males.
* Display: Used for attracting mates.
Essentially, the narwhal's "tusk" is a modified tooth that grows continuously throughout its life, forming the distinctive spiral shape. Its unique features and purpose continue to fascinate scientists.