Protocol for deriving proliferating primary fibroblast cultures from Malabar red snapper larvae for cytogenetic analysis

Here, we present a protocol for deriving primary fibroblast cultures from early-stage Malabar red snapper (Lutjanus malabaricus) larvae for cytogenetic analysis. We describe steps for dissociating larval tissues using trypsin and culturing them to establish proliferating fibroblast cells. We then detail procedures for arresting cells at metaphase by colchicine treatment, followed by hypotonic treatment, methanol-acetic acid fixation, and Giemsa staining to visualize chromosomes. This protocol yields clear metaphase spreads suitable for karyotype analysis and downstream cytogenetic applications.