In the last decade, significant progress has been made in development of marine and freshwater organism cell lines with utility for genomic studies. A variety of zebrafish cell lines have been developed, some of which maintain a normal karyotype for extended periods in vitro (Barnes and Collodi 2005) . Zebrafish cells in culture can be transfected with plasmid DNA using adaptations of approaches common for mammalian cells in vitro, and transient transfection methods have identified expression of genes under control of a number of mammalian and fish promoters. In addition, cell cultures from pufferfish (genera Fugu and Tetraodon) provide a biological complement to the genomic libraries derived to study the molecular biology of these animals, allowing the extension of this model to experiments in functional genomics. Multipassage cell cultures have been established from embryo and adult tissues of species of both of these pufferfish genera (Barnes and Collodi 2005) . One of the Fugu rubripes cultures has been maintained for more than 200 population doublings, and flow cytometry showed that the relative amount of DNA present in cultured cells was approximately 15% of that in human cells, as predicted by biochemical analysis. Telomerase, an enzyme associated with indefinite proliferation in mammalian cell cultures, was easily detectable in these cells, suggesting that the cultures are capable of indefinite growth.