Is it Serious?

If it is very severe, some orthomolecular specialists say it is asymptom of Vitamin B deficiency. (Pellagra)

Alcohol destroys vitamin B. 

Do you have your tongue pierced? I've seen that type of line on pierced tongues.

How's your nutrition?  Sounds like your digestive system needs an overhaul....start taking colloidal minerals, flax oil, essential fatty acids and B complex.  See a good Naturopath in your area.  Best wishes.

I AM A DENTAL ASSISTANT AND  It sounds like you may have something called a fissured tongue. It can appear wrinkled, with a deeply groved surface on the tongue. If this is what u have which this is exactly what it sounds like, I don't think that there is treatment for it. It can cause discomfort. You should go see a dentist. Also you will need a irrigating device to clean your "crack" which is probly a fissure. For now just make sure no food dedris gets left in the "crack" to reduce bacteria and when you get the chance see a dentist. They know more about your mouth than a general doctor would.

almost forgot a fissured tongue is not serious as long as you keep it clean food dedris can cause u discomfort

when you find out what it is exactly please inform me. Thank- you And BEST OF LUCK !!!