Longitudinal veins fused at base of wing into bifid
stalk. L3 delta-like at tip; L4 often incomplete at tip.
Wing margins often excised at tip of L4. Wings spread in proportion to their shortness. High temperature enhances and low
temperature produces overlapping of wild type. Stronger in
male than in female. Hypomorphic allele; females heterozygous
for bi and a deficiency for bi have outspread, crumpled, and
very flimsy wings with an extreme bifid fusion of the basal
regions of the longitudinal wing veins (Craymer and Roy, 1980,
DIS 55: 204). Enhances Bx alleles as well as sd, cp, and
vgnp (Waletzky). RK1.
Adults expressing omb1, the only allele studied in
phenotypic detail, are impaired in optomotor turning responses
in tests involving tethered or freely moving flies (Heisenberg
et al., 1978; Blondeau and Heisenberg, 1982; Kulkarni, Steinlauf, and Hall, 1988, Genetics 118: 267-285; Dushay, Rosbash,
and Hall, 1989, J. Biol. Rhythms 4: 1-27). The mutant is
also aberrant in orientation to vertical stripe (Heisenberg et
al., 1978). More detailed examination of "yaw torque" optomotor responses show that omb1 is restricted in responses to
stimulation of "frontal visual field", with mutant behavior
summarized as retaining "object responses" but missing "large
field responses" (Bausenwein et al., 1986). The mutant is
relatively normal in "lift/thrust" response to vertical pattern movement and in regard to landing response elicited by
front-to-back horizontal motion. Slow phototaxis, using Y-tube, was markedly subnormal (Dushay et al., 1989). Giant
arborizing fibers in lobula plate. Since isolation and the
original histological examinations, anatomical abnormalities
have become more pronounced, e.g., the optic lobes remain in
"pre-imaginal" orientation in some omb adults, viz., long axis
of medulla optic ganglia oriented more frontally than in
wild-type (Blondeau and Heisenberg, 1982); other behavioral
abnormalities: omb shows anomalous avoidance reaction, i.e.,
"antifixation" to objects in Y-maze test (Bulthoff, 1982,
Biol. Cybernet. 45: 63-70); courting males exhibit diminished
tracking responses of and turning responses to moving females
(Cook, 1980, Biol. Cybernet. 37: 41-51; Tompkins, Gross,
Hall, Gailey, and Siegel, 1982, Behav. Genet. 12: 295-307).
Visual stimulus-induced metabolic activity in the optic lobes
(monitored by distribution of radioactive 2-deoxyglucose) is
normal, suggesting that basic structure and function of ganglia distal to lobula plate is normal (Bulthoff and Buchner,
1985, J. Comp. Physiol. 156: 25-34). Without effect on
locomotor activity rhythm (Helfrich, 1986, J. Neurogenet.
3: 321-43).
Broad dark band on margins of all abdominal tergites, giving
abdomen superficial appearance of uniform darkness. Viability
of heterozygous female normal, of homozygous
female < 10% normal, and of male 30% normal. Qd/Df(1)bi4
exhibit homozygous Qd phenotype as well as bi-like phenotype;
Qd/bi and Qd/+ are normal with respect to bi (Banga, Bloomquist, Brodberg, Pye, Larrivee, Mason, Boyd, and Pak, 1986,
Chromosoma 93: 341-46). RK2.
