gene-expression patterns in the zebrafish correspond well The zebrafish belongs to the teleostean family of with the neuromeric model of Puelles and Rubenstein cyprinids (minnows), which includes other neurobiologi­ (1993) is very encouraging for further research in this cally well investigated species such as goldfish (Carassius model system, which holds the promise of revealing fun­ auratus) and carp (e. g. Cyprinus carpio). damental neurogenetic patterns and mechanisms in ver­ In a recent taxonomic revision (Barman, 1991), all spe­ tebrates. cies of the genus Brachydanio were reassigned to the genus Danio. Thus, the current species designation of the zebrafish is Danio (formerly Brachydanio) rerio (Hamil­ ton-Buchanan, 1822). As a cyprinid, the zebrafish belongs Generation of zebrafish mutants via saturation mutagenesis to the large group of ostariophysan teleosts (6000 species, The goal of saturation mutagenesis is to identify most - if Lauder and Liem, 1983). Most ostariophysans are charac­ not all- genes affecting early animal development and to terized by a sophisticated apparatus - the Weberian ossi­ understand their hierarchical, regulative role during de­ des - to transmit sound from the swim bladder to the velopment (for reviews, see: Mullins and Ntisslein-Vol­ inner ear. The ostariophysans belong to the most derived hard, 1993; Solnica-Krezel et aI. , 1994). This approach has group of teleosts, the euteleosts (17000 species), which recently been applied to the zebrafish system, and the re­ have three more basic teleostean outgroups, the oste­ sults are impressive.