At 9 to 10 days of age Whrnwi homozygotes display increased activity, decreased ability to right their selves, and are generally smaller than unaffected siblings. By 14 to 16 days of age homozygotes display head bobbing, circling, and an unsteady gate. Adults display head tossing and circling behavior and deafness is indicated by 20 days of age. Sackler and Weltman reported the average number of circles by a prodded 12-week old female homozygote to be 407 in 10 minutes. They found female homozygotes to have an increased metabolic rate and adrenocorticosteroid activity and decreased body weights. Homozygous males were reported to have decreased blood glucose and liver glycogen levels, decreased white blood cell and eosinophil counts, increased plasma albumin levels, and decreased globulin levels, in addition to decreased weight and increased food intake. (Lane 1963; Sackler and Weltman 1967, 1970, 1971.)
While the organ of Corti in whirler homozygotes shows normal gross cellular architecture at postnatal day (P) 35, stereocilia are shorter and stubbier. The inner hair cells have shorter stereocila as early as embryonic day (E) 18.5, are less than half the length of wild type by P5, and the normal graded variation in length and width along stereocilia ranks is diminished. While normal outer hair cell stereocillia develop a W-shaped array of ranks with a basal to apical increase in length, the outer hair cell stereocilia in whirler homozygotes develop a U-shaped or V-shaped array and the variation in length is diminished. The outer hair cells begin to degenerate by P60 while inner hair cells take longer to show degeneration, but both are undergoing degeneration by P80. (Kiernan et al., 1998; Holme et al., 2002.)
