When the “well-studied” is not as well-known as once thought: Immune cells from the Mediterranean sea urchin Paracentrotus lividus

Sea urchins are invertebrates belonging to the phylum Echinodermata, being organisms widely used in several areas of research, such as cell biology and immunology. In immunological studies involving echinoderms, whose focus ranges from understanding their basic immune responses to evolutionary questions, the species Strogylocentrotus purpuratus and Paracentrotus lividus are the most studied in the world. In this work, based on a BEPE-FAPESP internship (Vinícius Queiroz) conducted at the University of Palermo (Italy), we characterize the immune cells of the sea urchin P. lividus – a species that occurs throughout the Mediterranean Sea and in the North Atlantic Ocean, from Portugal to Scotland – and we compared them with those of Paracentrotus gaimardi, a completely unknown species from an immunological point of view, and that occurs on the Brazilian coast. Through an integrative analysis based on different methods, we observed that the four cell types commonly described for P. lividus (i.e. phagocytes, vibrating cells, and red and transparent spherulocytes) also occur in the Brazilian species. Additionally, a new cell type was observed for P. lividus, called granular spherulocyte, which was also found in P. gaimardi. Finally, the data obtained from the integrative approach allowed the development of a model capable of explaining the maturation process of spherulocytes. The results of this study show that: (1) the cells found in the species P. lividus are also observed in P. gaimardi; (2) although P. lividus is an immunologically well-known species, basic aspects still need to be clarified, since a new cell type has been discovered; (3) a more detailed analysis of the spherulocyte morphology and morphometry allowed the establishment of a model capable of explaining the maturation process of this cell type.

Full paper link: https://doi.org/10.1016/j.jcz.2022.06.008

Queiroz, V., Arizza, V., Vazzana, M., & Custódio, M. R. (2022). Comparative evaluation of coelomocytes in Paracentrotus sea urchins: Description of new cell types and insights on spherulocyte maturation and sea urchin physiology. Zoologischer Anzeiger, 300, 27-40.