Meiotic study on supernumerary microchromosomes of red fox (Vulpes vulpes)

MICROCHROMOSOMES OF THE ONTARIO RED FOX (VULPES VULPES): AN ATTEMPT AT CHARACTERIZATION

Characterization of the microchromosomes of the red fox, Vulpes vulpes Linn., was attempted through the examination of mitotic chromosomes using Giemsa banding, quinacrine banding, the silver nitrate-ammoniacal silver technique for staining nucleolar organizers, and autoradiographic procedures. Pachytene cells were examined in air-dried and squash meiotic preparations and in testicular tissue sectioned for light and electron microscopy. The results of banding procedures on mitotic chromosomes and the staining properties of the microchromosomes at pachytene indicated that the microchromosomes likely contain both heterochromatin and euchromatin. Autoradiographic analysis showed that the microchromosomes replicate during mid S phase while the Y chromosome, which is in the size range of the microchromosomes, replicates during late S phase. From these observations, it would appear that the microchromosomes may not be exclusively heterochromatic as hypothesized previously. With the use of the silver nitrate-ammoniacal silver technique, the presence of nucleolar regions were detected on specific macrochromosomes but not on any of the microchromosomes. Examination of pachytene chromosomes in air-dried and squash preparations, and of testicular tissue sectioned for light and electron microscopy, also indicated that the microchromosomes may not be involved in the organization of the nucleolus in the red fox.