EYE PIGMENTATION IN INSECTS — LODENSTEIN "i^J 



mutants (Schwartz, 1940 and 1941 ; Kiihn and Schwartz, 1942). It 

 has been shown, for instance, that the white eye of the Drosophila 

 mutant w remains colorless on transplantation into a wild-type host. 

 Likewise, if the pupal eye of the white-eyed Ephestia mutant wa or 

 that of the geometrid Ptychopoda mutant dec is transplanted into its 

 respective wild-type host pupa, it can be shown that the color develop- 

 ment of the mutant eye is autonomous. The reciprocal experiment, 

 namely, the grafting of a wild-type pupal eye into the pupa of the 

 mutant host, gives the same result. In all these combinations, there 

 is no influence of the graft on the eye color of the host, nor one of 

 the host on the eye color of the graft, although as other experiments 

 had shown, the wild-type forms contain tryptophane-derived diffusible 

 pigment precursors in their blood. Now, in the Ephestia mutant a the 

 formation of the brown eye pigment is kynurenine dependent. The 

 eye color of this animal can therefore be changed toward wild type 

 by the transplantation of a wild-type eye, because the graft produces 

 the pigment precursor kynurenine (a -^ substance) which is needed 

 for pigment formation in this mutant. Beyond this, it has been demon- 

 strated that when part of a pupal eye from an Ephestia mutant wa or 

 a Ptychopoda mutant dec is transplanted into the pupal eye region of 

 an Ephestia mutant a, the host eye pigmentation changes toward wild 

 type, while the grafted pieces develop the pigment characteristics of 

 their own genotypes. The implication of these results is clear. The 

 eye tissues of the wa and dec mutants release the pigment precursor 

 a -I- substance (kynurenine), although they cannot use this metabolite 

 for the formation of their own pigment. A similar situation has been 

 described for Drosophila, in the mutant of the w series (Ephrussi 

 and Chavais, 1937). 



To return to Periplaneta: The white-eyed Periplaneta mutant, as 

 shown by the studies of Ward and Hammen (1957), seems to accumu- 

 late tryptophane. Evidently, in Periplaneta as in the green Miisca 

 mutant, a genetic block prevents the transformation of tryptophane 

 into kynurenine. Yet the white-eyed Periplaneta mutant does not 

 change its eye color when in parabiotic fusion with a wild-type partner, 

 although as revealed by the feeding experiments, kynurenine is pres- 

 ent in the blood of the wild-type partner. Apparently, the white 

 Periplaneta eye is unable to utilize the kynurenine supplied by the 

 wild partner. But this suggests the presence of a genetic block at 

 still another point in the biosynthetic chain in the white Periplaneta 

 mutant. 



Now, it is known that the final pigment granules are bound to pro- 

 teiiiaceous carrier granules in the cytoplasm of the cell. As a matter 



