SEXING MONOMORPHIC AND JUVENILE BIRDS: AN EVALUATION OF CYTOLOGICAL METHODS
Sexing birds which display monomorphism among male and female members has presented problems to conservationists who are seeking to increase captive bird populations of endangered species. The present study was concerned with the application of four cytological techniques to a randomly selected and wide range of birds in an attempt to evaluate the methods as valid predictors of avian sex. Feather pulp samples collected from growing feathers provided a population of dividing and interphase cells without harming the birds in any way. Almost all of the samples were from juvenile birds in captivity at the Bronx Zoo. The results indicate that there is no single cytological method which will demonstrate avian sex, but that several of the techniques have validity and can be used alone or in combination. The variance in results is related to the quantity of heterochromatin in the avian genome and the method by which this is demonstrated. It has been previously reported that female birds exhibit a single heterochromatic body in interphase cells (Bloom, 1974; Mengden and Stock, 1976). This study indicates that male members of the Falconiformes and Gruiformes exhibit a single heterochromatic body more frequently than females. The species which show very little heterochromatin display a heterochromatic W chromosome in metaphase spreads while the W is occluded in species containing much heterochromatin. This had formerly been suggested as a positive confirmation of female sex (Mengden and Stock, 1976; Stefos and Arrighi, 1971). Fluorescent analysis of interphase cells gave consistent results in Caprimulgiformes. Results from other Orders were variable with some not exhibiting any fluorescence and others displaying no clear pattern for female versus male. C-banding and G- and C-banding provided good karyology of mitotic material. The best karyotypes were obtained from avian leukocyte microcultures which identify both micro- and macrochromosomes. This study provides a baseline evaluation of techniques. It provides a karyotype for the first time for several different species. It presents us with unanswered questions regarding the amount and function of heterochromatin and consistent cytological prediction of sex. Further investigation is planned.
COOK, IRIS MORDEY, "SEXING MONOMORPHIC AND JUVENILE BIRDS: AN EVALUATION OF CYTOLOGICAL METHODS" (1982). ETD Collection for Fordham University. AAI8219234.