Ultrastructural and Chemical Comparative Characteristic Studies on the Free Coelomocytes, Coelomic Epithelia and Fluids Between the Sea Urchins “Tripneustes gratilla” and “Echinometra mathaei”

Abstract

Remarkably, day after day, new echinoderm species were added to Phylum Echinodermata that include starfish, sea cucumbers, feather stars, and sea urchins. In this work, the sea urchins especially “Tripneustes gratilla” and “Echinometra mathaei” are the animals of choice due to their popularity, medical and economic importance. The coelomic epithelium and the free coelomocytes of both sea urchins were ultrastructurally studied in addition to the chemical analyses of their coelomic fluids, followed by protein docking. The coelomic epithelium (CE) of “Tripneustes gratilla” exhibits 4 main cells which are 1) basal cells, 2) short cells, 3) elongated-wide cells, 4) elongated-narrow cells, all of which are polygonal coelomocytes. Additionally, the CE of the sea urchin “Echinometra mathaei” is composed of 1) small cells, 2) red spherules 3) leucocytes, and 4) colourless spherules, which are irregular shape coelomocytes. The free coelomocytes of both sea urchins “Tripneustes gratilla” and “Echinometra mathaei” appeared in the amoeboid state (resembling the human phagocytic cells) with three distinctive forms: the leucocytes, the red spherules (type “1” and type “2”), and the colorless spherules. The nuclear egress was noticeable from the nuclei of the coelomic epithelial cells of both the adult sea urchins, “Tripneustes gratilla” and “Echinometra mathaei”. The CE of Tripneustes gratilla showed circular mitochondria with semi- circular cristae, while the CE of Echinometra mathaei showed elongated mitochondria. Chemically, the coelomic fluid extracted from both the adult sea urchins “Tripneustes gratilla” and “Echinometra mathaei” exhibited glycogen synthase kinase3-β protein. Ultrastructurally, the coelomic epithelium from both adult sea urchins “Tripneustes gratilla” and “Echinometra mathaei” showed 4 different units of coelomocytes, in which the coelomocytes of “Tripneustes gratilla” are elongated and polygonal; while the coelomocytes of Echinometra mathaei are morphologically irregular. In addition, the free coelomocytes from both adult sea urchins “Tripneustes gratilla” and “Echinometra mathaei” are irregular in shape resembling the human phagocytes, i.e. the shape meets the function. Chemically, the coelomic fluids extracted from both adult sea urchins “Tripneustes gratilla” and “Echinometra mathaei” exhibit glycogen synthase kinase3- β protein that could be used as an effective or potent agent for wound healing or skin regeneration.