MORPHOLOGY OF THE BASILAR PAPILLA OF THE BUDGERIGAR, MELOPSITTACUS-UNDULATUS

The budgerigar is a representative of the parrot-like birds that, like song birds, have developed complex communication signals. This specie s is interesting in a psychoacoustic sense, in that it shows unusually good frequency discriminative abilities above about 1 kHz. To begin t o understand whether the peripheral hearing organ plays a role in such specializations, we have carried out a quantitative study of the fine anatomy of the basilar papilla and compared it to data from other avi an species. The budgerigar basilar papilla is about 2.5 mm long in the living animal and contains about 5,400 hair cells. The hair cells of the papilla show regional specializations similar to those found in ot her birds and are described from scanning electron microscopic and lig ht microscopic studies. Regional changes in the basilar papilla, and i n the basilar and tectorial membranes are described from light microsc opic data. As noted for other avian species, the constellation of morp hologic features found in the budgerigar is unique. In general, the ha ir cell patterns of the budgerigar papilla showed fewer specialization s than found in, e.g., a songbird, the starling, but more than seen in a primitive land bird, e.g., the pigeon. There were no features that were obviously related to the unusual psychoacoustic performance of th is species. (C) 1993 Wiley-Liss, Inc.