Fig. 1

Research methods and design of experiments. a example of CL-activated UV–VIS spectrum of a fragment of luminescent spine (marked with a black circle in (b) of Echinometra sp. labeled with Mn²⁺ at 3 mg/L showing Mn²⁺ emission maximum at 632 nm (Mn²⁺ activation in Ca²⁺ and Mg²⁺ positions in calcite), b lateral view of spine showing no growth differences during and between labeling events (orange-red skeletal regions indicate enhanced Mn²⁺ concentrations due to twice Mn²⁺ labeling; dark ragions indicate growth in normal (without Mn²⁺) seawater), c lateral view of spine of Paracentrotus lividus labeled with Mn²⁺ at 61.4 mg/L without any signs of regeneration, d, lateral view of spine of control specimen of Paracentrotus lividus without any signs of luminescence, cutting fracture is delineated with dotted line, experimental design of trial (e) and main (f) experiments; each box represents a 24 h period