NEW INHERITED MUSCULAR DISORDER IN JAPANESE-QUAILS (COTURNIX-COTURNIX-JAPONICA)

Thirteen adult mutant (LWC strain) Japanese quails (Coturnix coturnix japonica), between the ages of 8 and 60 weeks were examined for a prog ressive muscular disorder. The disorder, inherited as an autosomal dom inant trait, was clinically apparent as early as 28 days of age; it wa s characterized by generalized myotonia, muscle stiffness, and muscle weakness. Affected birds were identified by their inability to lift th eir wings vertically upward and by their inability to right themselves when placed on their dorsum. Electromyographic studies in two mutant quails showed high-frequency repetitive discharges comparable to those of myotonic runs. These discharges persisted after nerve resection. T he distinctive histopathologic changes in the various muscles examined were ring fibers, sarcoplasmic masses, and internal migration of sarc olemmal nuclei. A slight decrease in the size of type IIB muscle fiber s and a slight increase in the size of type IIA fibers were observed i n the M. pectoralis thoracicus of affected quails. In older affected b irds, inter- and intrafascicular fatty infiltration with replacement o f type IIB fibers by fat cells was seen in the pectoral muscles. Singl e fiber necrosis, nonspecific lymphorrages, and variations in the musc le fiber size and shape were also noted. The typical muscle lesions an d multisystem involvement, which was manifested by testicular degenera tion and atrophy in the male LWC specimens and bilateral lenticular ca taracts in 6 of 13 affected mutant quails, suggest resemblance of this new inherited muscular disorder to myotonic dystrophy in man.