es ▁containing ▁e um el an in ▁are ▁e um el anos om es , ▁while ▁those ▁containing ▁ph ae om el an in ▁are ▁ph ae om el anos om es . ▁Mel an ocy te - st im ulating ▁h orm one ▁( MS H ) ▁bind s ▁to ▁the ▁Mel an oc ort in ▁ 1 ▁re ceptor ▁( MC 1 R ) ▁and ▁commits ▁mel an ocy tes ▁to ▁the ▁production ▁of ▁e um el an in . ▁In ▁the ▁absence ▁of ▁this ▁signal , ▁mel an ocy tes ▁produce ▁ph ae om el an in . ▁Another ▁chemical , ▁Ag out i ▁sign alling ▁pe pt ide ▁( AS P ), ▁can ▁attach ▁itself ▁to ▁MC 1 R ▁and ▁inter f ere ▁with ▁M SH / MC 1 R ▁sign alling . ▁In ▁many ▁m amm als , ▁variation ▁in ▁the ▁level ▁of ▁ASP ▁switch es ▁mel an ocy tes ▁between ▁e um el an in ▁and ▁ph ae om el an in ▁production , ▁resulting ▁in ▁col oured ▁patterns . ▁ ▁Mel an ocy tes , ▁and ▁the ▁parallel ▁mel an op hor es ▁found ▁in ▁fish es , ▁am ph ib ians , ▁and ▁re pt iles , ▁are ▁derived ▁from ▁a ▁strip ▁of ▁t issue ▁in ▁the ▁emb ry o ▁called ▁the ▁neural ▁cr est . ▁St em ▁cells ▁in ▁the ▁neural ▁cr est ▁give ▁rise ▁to ▁the ▁cells ▁of ▁the ▁autonom ic ▁nerv ous ▁system , ▁support ive ▁elements ▁of ▁the ▁ske leton ▁such