The ALDH superfamily shows considerable diversity among vertebrate genomes, with species in the current study showing between 14 and 25 putatively protein-encoding genes. Many of the gene duplications discussed here probably encode functional proteins. There are also a number of duplication events that give rise to non-functional pseudogenes. Names were assigned to the 'new genes' and 'pseudogenes' (Table 3) according to the ALDH nomenclature system established in 1999 [14]. The species-specific nomenclature system was used for zebrafish genes [15]. Pseudogenes were also named according to the standardised protocol [20].
