Unlike the equator and the Tropic of Cancer and the Tropic of Capricorn, the Prime Meridian and all lines of longitude are completely imaginary lines and have no significance with regard to the Earth or to its relationship with the sun.
Black hairy tongue typically results when projections on the tongue called papillae grow longer and don't shed like normal. This makes the tongue look hairy. Debris, bacteria or other organisms can collect on the papillae and result in discoloration. The cause of black hairy tongue can't always be determined.
1 Pimples on tongue can be a result of some kind of injury to the tongue caused by scraping or biting.  Oral thrush or oral candidiasis â a yeast infection â can also cause pimples on tongue. This is a fungal infection and you may see pimples on other parts of the body as well like the armpits or groin.