Skeletal ultrastructure of the calcified red alga Galaxaura oblongata, Hainan Island, China

• Published in: Review of palaeobotany and palynology 1999-02, Vol.104 (3), p.205-212
• Main Authors: Mu, Xinan, Riding, Robert
• Format: Article
• Language: English
• Subjects: algae; calcification; China; Galaxaura; Moniliporellaceae; Recent; Rhodophyta; ultrastructure
• ISSN: 0034-6667; 1879-0615
• DOI: 10.1016/S0034-6667(98)00061-X

Aragonite calcification in the red alga Galaxaura oblongata (Ellis et Solander) Lamouroux (Chaetangiaceae, Nemaliales) from southern China, occurs at three sites in the cortex: (1) intercellular spaces (ICS); (2) the cell wall; and (3) the inner surface of the cortex. The ICS is the principal site of calcification and contains aragonite mainly in the form of equidimensional granules ∼1–2 μm in size, although needle-like crystals up to 3 μm in length are also present locally. Granules range from densely to loosely packed. A dense and even layer peripheral to the ICS is interpreted to represent calcification of the cell wall. Coarser radial clumps of elongate crystals, forming a thin discontinuous layer on the inner surface of the cortex, resemble a cement fringe facing into the medulla, but form during the life of the alga. Calcification in these specimens shows similarities, and differences, to both coralline red algae, in which calcification is limited to the cell wall, and halimedacean green algae in which it is limited to the ICS. Some members of the Palaeozoic family Moniliporellaceae show similarities in their skeletal organization to Galaxaura.