Complete persistence of the primary somatosensory system in zebrafish.

The somatosensory system detects peripheral stimuli that are translated into behaviors necessary for survival. Fishes and amphibians possess two somatosensory systems in the trunk: the primary somatosensory system, formed by the Rohon-Beard neurons, and the secondary somatosensory system, formed by the neural crest cell-derived neurons of the Dorsal Root Ganglia. Rohon-Beard neurons have been characterized as a transient population that mostly disappears during the first days of life and is functionally replaced by the Dorsal Root Ganglia. Here, I follow Rohon-Beard neurons in vivo and show that the entire repertoire remains present in zebrafish from 1-day post-fertilization until the juvenile stage, 15-days post-fertilization. These data indicate that zebrafish retain two complete somatosensory systems until at least a developmental stage when the animals display complex behavioral repertoires. [Display omitted] • Rohon-Beard neurons are primary somatosensory neurons in the dorsal spinal cord of fishes and amphibians. • The entire population of Rohon-Beard neurons survives until free-swimming and juvenile stages in zebrafish. • Concomitant processes may have produced the illusion of disappearance over time. • Canonical cell death markers are absent in Rohon-Beard neurons. • Rohon-Beard neurons co-exist with neurons of the Dorsal Root Ganglia, which form later and are part of the secondary somatosensory system [ABSTRACT FROM AUTHOR]