Document Type : Primary Research paper
The sea urchins belong to the phylum of Echinodermata, have been founded in the middle or the lowest depth of marine coral reefs. The sea urchins have been used in many different studies for more than one century. As there was no comprehensive study concerning characterization of the Persian Gulf sea urchin, E. mathaei, this study was aimed to investigate the cytology of its coelomocytes. Study of cytology was performed using light, scanning, and electron microscopy and flow cytometry as well. Coelomic cavity of sea urchin is filled with coelomic fluid that houses free mobile populations of cells of sea urchin E. mathaei, specifically called coelomocytes. They are distinguished to seven types based on their morphological and ultrastructural characteristics including red and colourless spherulocytes, granular spherulocytes, small spherulocytes, vibratile cells, and phagocytic cells. Phagocytic cells exist in two distinct forms; the petaloid and filopodial cell. Flow cytometry analyses showed three cell populations. To our knowledge, this is the ﬁrst report describing ultrastructural details of the coelomocytes of E. mathaei.