No carriers of this mutation are identified in the colony today. They grow more slowly, and feed only a little after hatching. Some fluid accumulation in the head and trunk is common. The gene was originally identified in white animals obtained from the colony of D.R. Newth by L.E. DeLanney. This recessive mutation is characterized by increased numbers of melanophores, reduced numbers of xanthophores, and the absence of iridophores.
Adults are uniformly dark gray or black.
Homozygous microphthalmic larvae are identified around the time feeding begins. Their eyes are small, and the pigment cells often encroach upon the corneal surface. The effect may be asymmetric. Primarily affected are the olfactory organs, eyes, forebrain, and oral cavity. The pharynx, otic vesicles, hindbrain, notochord, and gill are apparently normal.