Karyotype analysis of the pumpkinseed Lepomis gibbosus (Actinopterygii, Centrarchidae) by chromosomal banding and in situ hybridization

Sunfish are widely distributed in their native North American freshwaters and in many other geographic regions, including Europe. In this work the cytogenetics of L. gibbosus were studied. In particular, the authors localized the heterochromatic regions and the major and minor ribosomal gene families. The nucleolar organizer region was localized terminally in the short arm of only one pair, a large acrocentric pair, using both FISH and silver staining. Furthermore, the 5S ribosomal gene family was also localized by FISH in only one pair, in the centromeric region of the smallest chromosome pair. NOR and 5S rDNA regions were both C-positive and CMA(3) positive. The CMA(3) positivity of the 5S ribosomal cluster is uncommon in fish, however, a similar situation has been found in M. salmoides, the only other centrarchid species studied with the same techniques. Moreover, the 5S ribosomal gene was sequenced and its molecular structure analysed.