Phagocytosis in vitro and in vivo in the Antarctic sea urchin Sterechinus neumayeri at 0°C

Phagocytosis of yeast by Sterechinus neumayeri phagocytic amoebocytes (PA) and their germicidal capacity was studied in vitro (1, 2 and 4 h) and in vivo (1, 2, 4, 8, and 12 h) at 0°C. The phagocytic capacity (PC), phagocytic index (PI), and germicidal capacity (GC) of the PA were calculated. Total number of coelomocytes varied between animals. In vitro, there was a significant increase of PC in all periods, and a significant difference of the PI and GC only between 1 and 2 h. In vivo, there was no significant difference of PC and the PI, but a significant increase in GC in different periods. PC and the PI index were significantly higher in vitro than in vivo for all studied periods, and GC only between 1 and 2 h. The PC and PI, compared with tropical sea urchins, were lower, despite the similar pattern, suggesting an effect of temperature on phagocytosis.[PUBLICATION ABSTRACT]