el ium . ▁When ▁the ▁st rom a ▁is ▁un p ig ment ed ▁but ▁the ▁ir is ▁p ig ment ▁ep ith el ium ▁is ▁not , ▁m amm al ian ▁eyes ▁appear ▁blue . ▁Mel an in ▁in ▁the ▁p ig ment ▁ep ith el ium ▁is ▁critical ▁for ▁visual ▁ac u ity ▁and ▁contrast . ▁ ▁L oss ▁of ▁mel an ogen esis ▁function ▁is ▁linked ▁to ▁the ▁gene ▁that ▁enc odes ▁ty ros in ase . ▁C ertain ▁alle les ▁of ▁this ▁gene , ▁T Y R , ▁at ▁the ▁Color ▁loc us , ▁cause ▁o cul oc ut aneous ▁al bin ism ▁type ▁ 1 ▁in ▁humans ▁and ▁the ▁familiar ▁red - ey ed ▁alb ino ▁conditions ▁in ▁m ice ▁and ▁other ▁m amm als . ▁ ▁In ▁other ▁verte br ates ▁Other ▁verte br ates , ▁such ▁as ▁fish es , ▁am ph ib ians , ▁re pt iles ▁and ▁birds , ▁produce ▁a ▁variety ▁of ▁non - mel an in ▁p ig ments . ▁Dis ruption ▁of ▁mel an in ▁production ▁does ▁not ▁affect ▁the ▁production ▁of ▁these ▁p ig ments . ▁Non - mel an in ▁p ig ments ▁in ▁other ▁verte br ates ▁are ▁produced ▁by ▁cells ▁called ▁chrom at op hor es . ▁Within ▁this ▁categor ization , ▁x anth op hor es ▁are ▁cells ▁that ▁contain ▁primarily ▁yellow ish ▁p ter id ines , ▁while ▁er yth roph ores ▁contain ▁primarily ▁or ang ish ▁car oten oid s . ▁Some ▁species ▁also