Adult neurogenesis in the Uruguayan teleost species Austrolebias charrua and Gymnotus omarorum.

Neurogenesis -the process by which new neurons are generated in the brain- is critical for nervous system development and plasticity. Adult neurogenesis underlies growth, repair, and adaptation to environmental changes. Vertebrates differ in their neurogenic and regenerative capacity, being particularly prominent in teleost as adult neurogenesis occurs throughout the rostral-caudal brain axis. This review examines adult proliferation and neurogenesis in the autochthonous Uruguayan teleost Austrolebias charrua and Gymnotus omarorum. A. charrua are annual fishes that live in temporary freshwater pools that dry up in the summer. The luminosity of the puddles varies greatly, and both vision and olfaction are crucial for the survival of this species. G. omarorum inhabits freshwater lagoons and rivers beneath dense masses of floating plants and have nocturnal habits. They rely on the electrosensory modality to navigate and communicate with conspecifics. These differences in habitats and predominant sensory modalities are reflected in the distinct brain morphotypes of G. omarorum and A. charrua. While G. omarorum is characterized by the hypertrophy of rhombencephalic cerebellum and electrosensory lateral line lobe, A. charrua has a well-developed olfactory bulb, mesencephalic tectum opticum, and torus longitudinalis. Accordingly, these regions have notorious neurogenic activity. Differences in neuroanatomy and distribution of neurogenesis in the brains of both species are discussed considering their life cycle and lifestyle. The comparison of these results with those reported in other teleost and vertebrates contributes to the understanding of the key role of neurogenesis in brain plasticity and evolution.