Pigmentation in the Orange Tunicate, Ecteinascidia turbinata

Lyerla, Timothy; Lyerla, Joann; Fisher, Marilyn

Ecteinascidia turbinata, a colonial ascidian of shallow waters, is characterized by the bright orange pigment in the adults' mantle tissue. The pigment is localized in fusiform organelles, approximately 3 to 6 u in length, that are organized into stellate shaped masses heavily concentrated at the siphon end and tapering in density toward the base of the zooid, which is almost colorless. Mature oocytes and early embryos of the species are dark yellow to orange, but their pigment is diffuse, not granular, and is solubilized in yolk platelets. The chemical nature of the pigment in E. turbinata has not been determined with certainty. The adult pigment was considered to be carotenoid on the basis of its similarity to the orange pigment in Synoicidae and Botryllidae species (George, 1939). The orange pigment in Ascidia mentula (Webb, 1939) and Phallusia mammilliata (Endean, 1960), however, has chemical properties entirely different from carotenoids, casting some doubt on the original interpretation based solely on comparative coloration between different species. The pigment in eggs and embryos has likewise not been subjected to direct analysis but designated "lipochrome" on the basis of its solubility in alcoholic solvents (Simkins, 1924). Also, there has not been agreement as to whether the stellate shaped masses of the mantle pigment are true cells. Nuclei could not be found in these aggregates in hematoxylin stained paraffin sections of mantle tissue, and it was concluded that they were not cells (Simkins, 1924). George ( 1938), however, found methyl green stained nuclei in orange blood cells of this species and postulated that these lodged in the mantle and became permanent fixtures of this tissue. The following studies attempt to resolve some of these questions concerning the chemical and cellular nature of the pigment in E. turbinata. It was felt that a better understanding of these properties of the pigment might allow some insights as to its functional role and perhaps provide a basis for any subsequent work on this little known pigmentary system.

Pigmentation in the Orange Tunicate, Ecteinascidia turbinata

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