The use of an integrative approach to identify coelomocytes in three species of the genus Holothuria (Echinodermata)

Author(s)

Queiroz, Vinicius ^[1] ; Mauro, Manuela ^[2] ; Arizza, Vincenzo ^[2] ; Custodio, Marcio R. ^[1] ; Vazzana, Mirella ^[2]

Affiliation

^[1] Univ Sao Paulo, Dept Fisiol Geral, Inst Biociencias, Sala 300, Rua Matao, Travessa 14, 101, Cidade Univ, BR-05508090 Sao Paulo - Brazil

^[2] Univ Palermo, Dipartimento Sci & Tecnol Biol Chim & Farmaceut S, Palermo - Italy

• Document type: Journal article
• Source: Invertebrate Biology; DEC 2021.
• Web of Science Citations: 0

Abstract

Coelomocytes in the Holothuroidea are traditionally identified according to their morphology through light, fluorescence, or electron microscopy. Former studies have typically used only one method, with few works combining two or more approaches. Studies using cytocentrifugation to study these cells are scarcer. Thus, for the first time, an integrative approach was used to compare coelomocytes in Holothuroidea. This approach consisted of living and stained cells, scanning electron microscopy (for spherule cells), and accurate morphometric analyses. Specifically, we used specimens of Holothuria grisea, Holothuria arenicola, and Holothuria tubulosa to test whether cytocentrifugation could be valuable in comparative studies with coelomocytes, whether an integrative approach could help to understand spherule cell diversity, and whether closely related species, even those having distinct geographic distributions and ecological requirements, would have a similar population of coelomocytes. Our results showed seven distinct cell types in these species, including phagocytes, fusiform cells, morula cells, acidophilic spherulocytes, spherulocytes, progenitor cells, and crystal cells. Total and differential cell counts, along with morphometric parameters, were similar among species. Morphometric analyses of spherule cells revealed consistent differences among the diameter of their cytoplasmic spherules, as well as a set of different morphotypes in acidophilic spherulocytes and spherulocytes. Cytospin preparations proved to be quite useful because they provided constant morphological and morphometric data, allowing accurate identification of the cell types and comparisons among species. Moreover, this study highlighted (1) that the spherule diameter is a good parameter to separate spherule cells and (2) a putative maturation process to acidophilic spherulocytes and spherulocytes. Lastly, we showed that the cells of these species are very similar, regardless of their geographic distribution and ecology. Thus, our work contributes to a better understanding of the coelomocytes in Holothuria, a genus with a wide geographic distribution. The present study may be useful to establish these species as important model organisms, as well as bring insights into the functions of coelomocytes. (AU)

• FAPESP's process: 15/21460-5 - Physiological function, chemical composition and ontogeny of Echinoid spherulocytes (Echinodermata).
• Grantee: Vinicius Queiroz Araújo
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 18/14497-8 - Physiological function and origin of the spherulocytes in the sea urchin Paracentrotus lividus (Echinodermata: Echinoidea)
• Grantee: Vinicius Queiroz Araújo
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate