Role of secondary metabolites and pigments in the epidermal tissues, ripe ovaries, viscera, gut contents and diet of the sea cucumber Holothuria atra |
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Authors: | W M Bandaranayake A Des Rocher |
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Institution: | (1) Australian Institute of Marine Science, P.M.B. No. 3, Townsville, MC, Townsville, Queensland 4810, Australia Fax: +61 (0) 747 725 852 E-mail: banda@aims.gov.au, AU |
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Abstract: | The epidermal tissues, ovaries, viscera, gut contents, and the diet of Holothuria atra (Jaeger), collected from the Great Barrier Reef (GBR), Australia, just prior to spawning, contained carotenoid pigments,
mycosporine-like amino acids (MAAs) and three other metabolites in varying proportions. Mycosporine-glycine (mycosporine-gly),
palythine, asterina-330, shinorine, mycosporine-2-gly, porphyra-334, and palythinol were present in the epidermal tissues.
Mycosporine-gly was the major MAA in the epidermal tissues, gut contents and the diet, and the only MAA present in the ripe
ovaries and the viscera. Gadusol, a metabolite with antioxidant properties, which co-occurs with MAAs, and in certain instances
with trace amounts of 6-deoxygadusol in unfertilised and fertilised eggs and developing larvae of some marine invertebrates
and vertebrates, was absent from H. atra. However, 6-deoxygadusol, with similar physical and chemical properties to gadusol, and the proposed biosynthetic precursor
of MAAs, was present, but only in the ovaries. This is first report of the presence of this proposed biogenetic precursor
of MAAs in significant amounts in a marine invertebrate. Approximately 90% of the total carotenoids of the epidermal tissues,
ovaries and viscera of H. atra are highly oxidised, the main component being astaxanthin followed by canthaxanthin. These were the major carotenoids present
in the ovaries and the total carotenoid content was highest in the ovaries. β-carotene, a common egg carotenoid, was present
in trace quantities in the ovaries but, along with the xanthophylls lutein and zeaxanthin, it occurred in significant amounts
in the gut contents and the diet of H. atra. Carotenoid patterns in the epidermal tissues and viscera were strikingly similar, containing β-carotene, canthaxanthin,
astaxanthin, zeaxanthin, lutein, phoenicoxanthin and echinenone. The alkaloids homarine and isomeric trigonelline, (structurally
unrelated to MAAs) and 6-deoxygadusol were present only in the ovaries and the viscera. It is suggested that these metabolites
and pigments are either involved with photoprotection or reproduction, or associated with both processes. The origin, biogenetic
relationships and the roles of these metabolites and pigments in H. atra are discussed.
Received: 21 November 1997 / Accepted: 14 September 1998 |
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