Eye disk differentiation in the wax moth: induction in vitro.

Ecdysterone-induced differentiation of Galleria mellonella compound eyes in vitro is critically dependent on the age of the donor. It is greatest in explants from young prepupae, decreases with increasing donor age, and is absent in explants from 4-6 hour pupae. Failure of eye disks from pupae to differentiate in vitro seems to be the consequence of exposing them to culture conditions at a susceptible time in their development for, unlike eye disks from prepupae, they do not develop when removed from the medium and implanted into competent hosts. The explants most responsive in vitro are more liable to submerge, with resulting inhibition of development. Three media allow differentiation of adult eye structures, and one of these is suitable without adding macromolecular compounds. Ecdysterone is essential, and will elicit ommatidia formation when it is added to the medium at concentrations ranging from 0.1-20 mug/ml. Rubrosterone is ineffective at 1.0 mug/ml of medium. In the best-differentiated explants each ommatidium consists of 8-10 pigmented retinal cells surrounding a rhabdom-like core, and their axons can be traced to an enlarged optic nerve. Crystalline cones, adult cuticle in the form of facets (corneal lenses), and pigment cells also are formed.