Identification of manubrium pigments in two species of Turritopsis medusae (cnidaria, hydrozoa) in Japan

In Turritopsis rubra and T. sp., which are c. 10 mm and several mm in diameter and are distributed in northern and southern Japan, respectively, the same volume of their manubriums, c. 0.1 g in the total wet weight, were cut out under a stereomicroscope and major pigments were extracted with acetonitrile, then analyzed at 480 nm with high performance liquid chromatography (HPLC). As a result, two sharp peaks were found in T. rubra, of which manubrium is scarlet color, and these two kinds of pigment substances were comparatively analyzed with standard astaxanthin and canthaxanthin by HPLC, and proved to be these two chemical compounds. In contrast, in T. sp., of which manubrium is pale yellow, only astaxanthin was found. In relation to function of pigments and ecology of medusae, biological meaning of their differential coloration is discussed, and tentative suppositions, prevention of leak of bioluminescent baits within the manubrium and sun-screening effects, are proposed.