Abstract
Introduction: Echinoderm coelomocytes have traditionally been investigated through a morphological approach using light microscopy, which relies on the idea of constant cell shape as a stable character. However, this can be affected by biotic or abiotic conditions. Objective: To analyze if the consistency in cell morphology offered by the cytocentrifugation method, might be used as a convenient tool to study echinoderm coelomocytes. Methods: Cells of Echinaster (Othilia) brasiliensis (Asteroidea), Holothuria (Holothuria) tubulosa (Holothuroidea), Eucidaris tribuloides, Arbacia lixula, Lytechinus variegatus, and Echinometra lucunter (Echinoidea) were spread on microscope slides by cytocentrifugation, stained, and analyzed through light microscopy. Additionally, fluorescence microscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy were applied to cytospin preparations, to complement the analysis of granular and colorless spherulocytes of Eucidaris tribuloides. Results: Altogether, 11 cell types, including phagocytes, spherulocytes, vibratile cells, and progenitor cells were identified in the samples analyzed. The granular spherulocyte, a newly-described cell type, was observed in all Echinoidea and was very similar to the acidophilic spherulocytes of Holothuria (Holothuria) tubulosa. Conclusions: Cytocentrifugation proved to be versatile, either as the main method of investigation in stained preparations, or as a framework on which other procedures may be performed. Its ability to maintain a constant morphology allowed accurate correspondence between live and fixed/stained cells, differentiation among similar spherulocytes as well as comparisons between similar cells of Holothuroidea and Echinoidea.
Highlights
Echinoderm coelomocytes have traditionally been investigated through a morphological approach using light microscopy, which relies on the idea of constant cell shape as a stable character
Considering the inherent advantages of cytocentrifugation, as stated by Qing-fan (1986), and the scarcity of studies using this method to analyze coelomocyte morphology, this work aims to address three main questions: 1) Is cytocentrifugation a satisfactory method to investigate coelomocyte morphology in Echinodermata? 2) Could cytospin slides be used in conjunction with other techniques? 3) Would cytocentrifugation be useful in comparing cell morphology of different echinoderm groups? Considering all analyzed groups, i.e. Asteroidea, Holothuroidea, and Echinoidea, we found eleven cell types, which were observed in both live and stained preparations
Echinoid coelomocytes were collected according to Queiroz and Custódio (2015), by inserting a syringe needle preloaded with 0.5 mL of isosmotic anticoagulant solution into the peristomial membrane and 0.5 ml of coelomic fluid was withdrawn from each sea urchin
Summary
Echinoderm coelomocytes have traditionally been investigated through a morphological approach using light microscopy, which relies on the idea of constant cell shape as a stable character. This can be affected by biotic or abiotic conditions. Objective: To analyze if the consistency in cell morphology offered by the cytocentrifugation method, might be used as a convenient tool to study echinoderm coelomocytes. Methods: Cells of Echinaster (Othilia) brasiliensis (Asteroidea), Holothuria (Holothuria) tubulosa (Holothuroidea), Eucidaris tribuloides, Arbacia lixula, Lytechinus variegatus, and Echinometra lucunter (Echinoidea) were spread on microscope slides by cytocentrifugation, stained, and analyzed through light microscopy. Its ability to maintain a constant morphology allowed accurate correspondence between live and fixed/stained cells, differentiation among similar spherulocytes as well as comparisons between similar cells of Holothuroidea and Echinoidea
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