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.
Smoking or chewing tobacco & poor oral hygiene may contribute to the formation of a black hairy tongue. Hair does not actually grow on your tongue but gives that appearance to some degree as the filiform papillae of your tongue elongate . The use of a tongue blade daily may prevent, eliminate or control this issue. Chewing tobacco can also cause cancer which is more serious! In brief: May contribute to.