Cross references:    Globin     Muscle Innervation       
Motor Neuron Evolution    Motor Nerve Organization      
Medial Motor Column
Fast vs. Slow Twitch Muscles    

Shark Muscles

Heme (Wiki)   
    "A haem (British English) or heme (American English) is a chemical compound of a type known as a prosthetic group consisting of an Fe2+ (ferrous) ion contained in the centre of a large heterocyclic organic ring called a porphyrin, made up of four pyrrolic groups joined together by methine bridges. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are known as hemoproteins. Hemes are most commonly recognized in their presence as components of hemoglobin, the red pigment in blood, but they are also components of a number of other hemo-proteins such as myoglobin, cytochrome, endothelial nitric oxide synthase, catalase, etc. "  
My comment:     
    The reference refers to "hemoglobin, the red pigment in blood", but it does not say that all hemes are red.