Short-term juvenile crowding arrests the developmental formation of dendritic spines on tectal interneurons in jewel...

Development of jewel fish tectal interneurons was measured as a function of crowded development. The number of dendritic spines on the apical dendrites of pyriform interneurons was counted in the stratum album centrale plexiform layer because previous research indicated that this was the region in which both social deprivation and acute juvenile crowding produced neuronal deficits. Results showed that 100- and 130-day-old uncrowded juveniles had spine densities equivalent to 160-day-old juveniles crowded at 15 fish/3.6 liter for 60 days. Thus, no spine formation occurred after the onset of crowding. Sibling 160-day-old juveniles reared in the uncrowded condition (1 fish/4.6 liter) had already acquired the normal complement of spines exhibited by 4-year-old adults reared at low density (1 fish/25 liter). These results show that acute crowding can arrest the normal course of neuronal development in juvenile jewel fish.