A SIMPLE AND RAPID CHROMOSOME PREPARATION METHOD OF NILE TILAPIA Oreochromis niloticus WITHOUT METAPHASE ARRESTING TREATMENTS

Most chromosome preparation methods use colchicine or colcemid in order to arrest cell division during metaphase, which usually involves the use of high cost materials and longer time. This research was aimed to simplify and rapidly fish chromosome preparation method without using colchicine or colcemid as metaphase arresting agents.

Ten Nile tilapia fish of different ages, namely 1-, 2- and 3-month-old were used in this research. Chromosome preparation method with metaphase arresting agent (colchicine) of 1-month-old fish was also used as control. Tissues were collected on the caudal fin of the fish. Chromosome spreads were easily observed, using Giemsa or silver staining, five hours after the whole preparation process. The results showed that the 1- and 2-month-old fish had better mitotic index (0.008 and 0.01, respectively) compared to those of the     3-month-old fish, 0.005 (Table 1). The chromosome spreads of tilapia fish were easily distinguished using either Giemsa or silver stains. No significant difference was observed in term of chromosome spreads between treatments without or with metaphase arresting agents (Figure 1). Chromosomes of tilapia are relatively easy to be observe and confirm, because of the uniqueness of their marker homologues giant chromosome. This method advantages did not only simple and rapid, cost-efficient and applicable for ploidy level determination, but also allows fish alive for next evaluations.