Gambaran Kariotipe Ikan Tikus, Bronze Cory (Corydoras aeneus Gill, 1858)

Abstract

Corydoras aeneus is a freshwater ornamental fish native to the waters of South America. It is exhibiting unique behavior of cleaning aquarium walls with its mouth. C. aeneus locally known as the mouse fish, and it has been widely cultivated in Indonesia. This research aims to determine the karyotype characteristics of mouse fish distributed in Indonesia, specifically from two different cultivation locations: Medan and Bogor. This research used a descriptive method with fish samples obtained from ornamental fish sellers in Medan, acclimatized for 4 days. The fish were immersed in a 0.007 % colchicine solution for 8 hours to obtain chromosomes at the metaphase stage. Chromosome preparations were made using the solid tissue technique from fish gills, stained by 5% Giemsa solution, and observed under a AmScope microscope. Karyotype analysis was performed using Adobe Photoshop CS3 and IdeoKar 1.3 software. The analysis results show that Corydoras aeneus from Medan and Bogor have the same diploid chromosome number of 2n = 56, but there are differences in chromosome size and shape. C. aeneus from Medan has the largest chromosome measuring 11.62 µm, with a total complement chromosome length of 202.43 µm, a total form percentage of 44.08 %, a karyotype asymmetry index of 55.91 %, and an average centromeric index of 0.42 µm. Meanwhile, C. aeneus from Bogor has the largest chromosome measuring 13.29 µm, with a total complement chromosome length of 214.31 µm, a total form percentage of 44.22 %, an asymmetry index of 55.77 %, and an average centromeric index of 0.42. C. aeneus from Medan has 23 pairs of metacentric chromosomes, 4 pairs of submetacentric chromosomes, and 1 pair of telocentric chromosomes. In contrast, those from Bogor has 24 pairs of metacentric chromosomes, 2 pairs of submetacentric chromosomes, and 2 pairs of telocentric chromosomes. The differences in chromosome size and shape indicates genetic variation between populations. Corydoras aeneus from Medan shows a more advanced evolutionary level with a slightly higher karyotype asymmetry index compared to those from Bogor. Although there is genetic variation between populations, it does not cause morphological differences in C. aeneus.