FOURIER TRANSFORM INFRARED MICROSPECTROSCOPY AS A TOOL TO IDENTIFY MACROALGAL PROPAGULES1

Authors

  • Alecia Bellgrove,

    1. School of Life and Environmental Sciences, Deakin University, PO Box 423, Warrnambool, Victoria 3280, Australia
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  • Hiroshi Kihara,

    1. Department of Physics, Kansai Medical University, 18-89 Uyama-Higashi, Hirakata 573-1136, Japan
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  • Akira Iwata,

    1. IR FEL Research Center, Research Institute for Science and Technology, The Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
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    • 3

      Present address: The New Industry Research Organisation, 1-5-2, Minatojima-minamimachi, Chuo-ku, Kobe, 650-0047, Japan.

  • Masakazu N. Aoki,

    1. Shimoda Marine Research Centre, University of Tsukuba, 5-10-1 Shimoda, Shizuoka 415-0025, Japan
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  • Philip Heraud

    1. School of Biological Sciences, Monash University, Wellington Rd, Clayton, Victoria 3800, Australia
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    • 4

      Present address: Monash Immunology and Stem Cell Laboratories, Monash University, Building 75, Wellington Rd., Clayton, Victoria 3800, Australia.


  • 1

    Received 18 January 2008. Accepted 28 January 2009.

Abstract

Understanding of macroalgal dispersal has been hindered by the difficulty in identifying propagules. Different carrageenans typically occur in gametophytes and tetrasporophytes of the red algal family Gigartinaceae, and we may expect that carpospores and tetraspores also differ in composition of carrageenans. Using Fourier transform infrared (FT-IR) microspectroscopy, we tested the model that differences in carrageenans and other cellular constituents between nuclear phases should allow us to discriminate carpospores and tetraspores of Chondrus verrucosus Mikami. Spectral data suggest that carposporophytes isolated from the pericarp and female gametophytes contained κ-carrageenan, whereas tetrasporophytes contained λ-carrageenan. However, both carpospores and tetraspores exhibited absorbances in wave bands characteristic of κ-, ι-, and λ-carrageenans. Carpospores contained more proteins and may be more photosynthetically active than tetraspores, which contained more lipid reserves. We draw analogies to planktotrophic and lecithotrophic larvae. These differences in cellular chemistry allowed reliable discrimination of spores, but pretreatment of spectral data affected the accuracy of classification. The best classification of spores was achieved with extended multiplicative signal correction (EMSC) pretreatment using partial least squares discrimination analysis, with correct classification of 86% of carpospores and 83% of tetraspores. Classification may be further improved by using synchrotron FT-IR microspectroscopy because of its inherently higher signal-to-noise ratio compared with microspectroscopy using conventional sources of IR. This study demonstrates that FT-IR microspectroscopy and bioinformatics are useful tools to advance our understanding of algal dispersal ecology through discrimination of morphologically similar propagules both within and potentially between species.

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