Eye size variably reduced depending on allele (see
table); expressivity more variable for some alleles than for
others. Tetragonal packing of facets and face-centered
tetragonal bristle lattice (eyR) in place of hexagonal array
of wild type [Hartman and Hayes, 1971, J. Hered. 62: 41-43
(fig.)]; associated with a failure of the horizontal secondary
pigment cell to expand to give rise to the horizontal boundaries between ommatidia [Ready, Hanson, and Benzer, 1976,
Dev. Biol. 53: 217-40 (fig.)]. Some ey2 flies show duplications of antennae or antennal segments with or without duplication of aristae; extra maxillary structures also observed
(Shatouri, 1963, Caryologia 16: 431-37). Optical disks
reduced in size [(ey1) Richards and Farrow, 1922, Proc.
Oklahoma Acad. Sci. 2: 41-45; (ey2) Medvedev, 1935, Z.
Indukt. Abstamm. Vererbungsl. 70: 55-72 (fig.); 1935, Tr.
Inst. Genet. Akad. Nauk SSSR 10: 119-51; Steinberg, 1944,
Proc. Nat. Acad. Sci. USA 30: 5-13; (ey4) Chen, 1929, J. Morphol. 47: 135-99]. Degenerating cells abundantly observed in
the optic disks of third-instar larvae of ey2 [Fristrom, 1969,
Mol. Gen. Genet. 103: 363-79 (fig.); Ransom, 1979, J.
Embryol. Exp. Morphol. 53: 225-35]. Expressivity sensitive
to genetic background [(ey4) Spofford, 1956, Genetics
41: 938-59; (ey1, ey2, ey4, eyK) Hunt and Burnet, 1969,
Genet. Res. 13: 251-65]. Phenotype also responds to developmental temperature, larval density, and composition of medium.
Eye size reported to increase with increased temperature in e1
(Baron, 1935, J. Exp. Zool. 70: 461-90) and eyK (Sang and
Burnet, 1963, Genetics 48: 1683-99) but to decrease in eyW
(Meyer, 1959, DIS 33: 97). Phenotype less extreme in flies
raised under crowded conditions at 18 but not 25 (Sang and
Burnet, 1963; see also Chester, 1971, DIS 46: 62-63). Eye
size of four alleles increased by cholesterol deprivation and
decreased by dietary deficiencies in thiamine or RNA (Hunt and
Burnet, 1969). Larval feeding of lactamide to ey2 causes
decreased eye size, which is of opposite sign from its effect
on B (Grant and Rapport, 1980, DIS 55: 53); no such effect of
lactamide on eyK observed by Sang and Burnet (1963). ey2
flies exhibit normal visual orientation in Y maze (Bulthoff,
1982, DIS 58: 31). ey2, ey4, and eyK in combination with eyg
(3-35.5) results in almost complete curtailment of eye
development and synthetic lethality, with the major lethal
crisis at the end of the pupal stage and a minor lethal phase
at pupation; rare surviving adults have brain in anterior
thorax [Hunt, 1970, Genet. Res. 15: 29-34 (fig.)].
Eyes of heterozygotes small, outline irregular, displaced toward top and rear. Head large, often with duplicated
antennae or ocelli. Basitarsus broadened distally and incompletely separated from second tarsal segment owing to interruptions of the intersegmental membrane. Polarity of bract-bristle arrangement locally reversed in regions of membrane
gaps [Poodry and Schneiderman, 1976, Wilhelm Roux's Arch. Dev.
Biol. 180: 175-88 (fig.)]. 27-48 sex-comb teeth disposed in
more-or-less parallel longitudinal rows in males; number of
transverse-bristle rows increased in females (Stern and Tokunaga, 1967, Proc. Nat. Acad. Sci. USA 57: 658-64). Extra leg
joints tend to form as mirror-image duplications proximal to
the normal joint between the first and second tarsal joints
(Held, Duarte, and Derakhshanian, 1986, Wilhelm Roux's Arch.
Dev. Biol. 195: 145-57). Clones of ey+ tissue in eyD/+ background exhibit eyD/+ phenotype (Stern and Tokunaga, 1967), but
both ey+ leg disks transplanted into eyD hosts and the
reciprocal transplant develop autonomously (Tokunaga, 1970,
Dev. Biol. 18: 401-13). fj eyD flies have but three tarsal
joints (Postlethwaite and Schneiderman, 1975, Annu. Rev.
Genet. 7: 381-433). Fully dominant in triplo-4 flies (Sturtevant, 1936, Genetics 21: 448). Eye size of B; eyD/+ males
larger than of B alone. Produces extreme phenotype in combination with D. D/+; eyD/+ almost completely lethal (Sobels,
Kruijt, and Spronk, 1951, DIS 25: 128). Homozygous lethal;
two lethal crises, one during first or second larval instar
and the other just prior to or during pupal stage. Cell
degeneration observed in optic disks of homozygous second-instar larval (Ransom, 1979, J. Embryol. Exp. Morphol.
53: 225-35). Larvae which are unable to pupate rescuable by
injection of α-ecdysone (Arking, 1969, J. Exp. Zool.
171: 285-96). Homozygotes reaching pupal stage lack adult
derivatives of eye-antennal disks; adult derivatives are
formed by eyD/eyD eye-antennal disks transplanted into wildtype hosts; brain present but number of cortical cells
severely reduced (Arking, Putnam, and Schubiger, 1975, J.
Expt. Zool. 193: 301-12). RK2.