“…In recent years, mounting evidence has confirmed that descending neurons of lampreys known to be “bad regenerators” suffer a process of delayed death and are also “poor survivors” after a complete SCI (Figure 1C ; Shifman et al, 2008 ; Barreiro-Iglesias and Shifman, 2012 , 2015 ; Busch and Morgan, 2012 ; Hu et al, 2013 , 2017 ; Zhang et al, 2014 ; Barreiro-Iglesias, 2015 ; Fogerson et al, 2016 ; Barreiro-Iglesias et al, 2017 ). The occurrence of cell death in a subset of identifiable descending neurons after SCI in lampreys was confirmed based on the disappearance of Nissl staining (Figure 1C ), the loss of neurofilament expression, the absence of labeling when using retrograde tracers (Shifman et al, 2008 ), and the early staining of these neurons with Fluoro-Jade C (Busch and Morgan, 2012 ; Barreiro-Iglesias et al, 2017 ), which is a marker for degenerating neurons. In addition, the appearance of TUNEL staining (Shifman et al, 2008 ; Hu et al, 2013 ) and activated caspases (Figure 1C ; Barreiro-Iglesias and Shifman, 2012 , 2015 ; Hu et al, 2013 ; Barreiro-Iglesias et al, 2017 ) in the soma of axotomized descending neurons suggests that their death after SCI is apoptotic.…”