Special physiological attributes exhibited by many evolutionarily diverse aquatic organisms have led to the increased appreciation of their importance as models of human disease. These characteristics have been exploited experimentally to further understanding of human immunology, genomics, stem cell and cancer biology, pharmacology, toxicology and neurobiology. Historically, marine vertebrates provided critical insights into fundamental mechanisms of physiological processes, and the value of these organisms has not been diminished by the advent of molecular approaches. Membrane transporters that are the sites of action of diuretic drugs were first cloned from specialized organs in marine species (Gamba et al. 1993; Xu et al. 1994) . Mutagenesis studies in bony fish generated a spectrum of biologically relevant and distinct phenotypes (Naruse et al. 2004; Walter et al. 2004 ). Large-scale genetic screens produced more than 500 zebrafish mutants, many with phenotypes similar to human disorders (Dooley and Zon 2000) . Immunogenetic studies in carp, salmonids and other species are contributing to the growing database of marine vertebrate genomics Fujiki et al. 2001 Fujiki et al. , 2003 Tomana et al. 2002; Ishikawa et al. 2004) .