SPINELESS-ARISTAPEDIA [ssa]
Lindsley & Grell, 1972, p. 237
origin: Spontaneous.
discoverer: Balkaschina, 1926.
references: 1929, Arch. Entwicklungsmech. Organ. 115: 448-63 (fig.).
phenotype: Antennae and aristae tarsuslike; size approaches normal tarsus; two claws at tip. Third joints of antennae like parts of a tarsal row but with broad, flat, platelike lobes below. Bristles like those of a medium to slight Minute. Frequent extra dorsocentral bristles. Development of tarsi in place of aristae enhanced by low temperature (Villee, 1943, Genetics 28: 94). Antennal disks from ssa larvae give rise to leglike structures when transplanted into wild-type hosts; when disks are pretreated with colchicine the developing structures more aristalike (Vogt, 1947, Experientia 3: 156-59). Disks from wild-type larvae also develop autonomously when transplanted into ssa hosts (Braun, 1940, Genetics 25: 143-49). Similar results observed in mosaics resulting from X-ray-induced somatic exchange (Roberts, 1964, Genetics 49: 593-98). ssa/ss has normal aristae but bristles like ssa or slightly smaller. Regions of aristae converted into tarsi not affected by mutants affecting aristae, e.g., th and al, but are affected by those operating on tarsi, e.g., fj, d, app, and ey (Waddington, 1939, Growth, Suppl. 1, pp. 37-44; Braun, 1940). RK1.
other information: To the left of ssa40a (Hexter).
color figure: P. A. Otto (original)
b & w figure: Bridges and Brehme, 1944, Carnegie Inst. Wash. Publ. No. 552: 179 (original drawn by Edith M. Wallace)