Analisis Kariotipe Ikan Hantu Hitam, Black Ghost (Apteronotus albifrons Linnaeus, 1766)

Abstract

The Black Ghost fish (Apteronotus albifrons) is an introduced species originating from the Amazon River, South America. The Black Ghost fish has a laterally compressed body shape and a dark black coloration. It is classified as a nocturnal species, being active at night. This study aims to analyze the karyotype characteristics of the Black Ghost fish using the IdeoKar 1.3 software. Fish samples were obtained from ornamental fish traders in Medan City, then acclimatized for 4 days at the Genetics and Molecular Biology Laboratory. A colchicine treatment of 0.007% was applied for 9 hours to induce chromosome metaphase. Chromosome preparations were made using the squash technique from gill tissue and stained with 5% Giemsa. Observations were carried out using a microscope and analyzed morphometrically with the aid of IdeoKar 1.3 and Adobe Photoshop CS3 software. The results showed that the Black Ghost fish has a diploid chromosome number of 2n = 24, consisting of 9 pairs of metacentric chromosomes, 1 pair of submetacentric chromosomes, and 2 pairs of telocentric chromosomes. The largest chromosome measured 5.34 μm with a maximum arm ratio of 2.25, the highest r-value of 0.93, and the maximum relative length percentage of 11.42%. The total haploid complement length (HCL) was 46.75 μm, the total form percentage (TF%) was 42.28%, the asymmetry index (AsK%) was 57.71%, and the mean centromeric index (XCI) was 0.38. These results indicate that the karyotype of the Black Ghost fish is classified as asymmetric with morphological variations that are likely influenced by genetic and geographical factors.