SENSITIVITY OF VISUAL RECEPTORS OF CAROTENOID-DEPLETED FLIES: A VITAMIN A DEFICIENCY IN AN INVERTEBRATE.

House flies (Musca domestica) raised under sterile conditions on a diet lacking carotenoids and retinol (vitamin A) have visual receptor sensitivities -as assessed electroretinographically-which average more than 2 log units below normal, both in the near ultraviolet (340 mmicro) and visible (500 mmicro) regions of the spectrum. Loss of sensitivity can be prevented by the addition of beta-carotene to the larval food. Flies reared for several generations on a carotenoid-free diet, but under conditions where the adults are not kept sterile, do not show a further loss of sensitivity. It is suggested that carotenoid stored in the egg prevents complete blindness in the first generation, and that microorganisms can supply small amounts of carotenoid and thereby prevent complete blindness in the second and successive generations.