Caulerpa <strong>taxifolia</strong> <strong>in</strong> Moreton Bay Jane Thomas -3- Introduction C. <strong>taxifolia</strong> native distribution C. <strong>taxifolia</strong> <strong>in</strong>troductions Figure 1. Distribution of native and <strong>in</strong>troduced Caulerpa <strong>taxifolia</strong> populations around the world.
2.1 GENERAL BIOLOGY Caulerpa <strong>taxifolia</strong> <strong>in</strong> Moreton Bay The morphology of the Caulerpa thallus is a horizontal creep<strong>in</strong>g stolon from which the photosynthetic fronds and anchor<strong>in</strong>g rhizoid pillars arise. All Bryopsidophyceaen macroalgae, <strong>in</strong>clud<strong>in</strong>g Caulerpa are coenocytic, that is, the protoplasm is mult<strong>in</strong>ucleate and cont<strong>in</strong>uous and not separated by <strong>in</strong>ternal cell walls, although <strong>in</strong>ternal support structures are present (Clayton and K<strong>in</strong>g, 1990). Fragmentation is an efficient mode of reproduction <strong>for</strong> coenocytic green macroalgae, and fragments as small as 2 mm may propagate <strong>in</strong>to full-size plants (Brück and Schnetter, 1993; Walters and Smith, 1994; Smith and Walters, 1999). Caulerpa conta<strong>in</strong>s a suite of toxic secondary metabolites, the major one of which is a sesquiterpenoid called caulerpenyne (Amico et al., 1978; Paul and Fenical, 1986; 1987). The array of tox<strong>in</strong>s <strong>in</strong> C. <strong>taxifolia</strong> are antiviral (Nicoletti et al., 1999), neurotoxic (Brunelli et al., 2000), cytotoxic and cell growth <strong>in</strong>hibitors (Barbier et al., 2001). They also display active or toxic effects on phytoplankton (Lemée et al., 1997), mar<strong>in</strong>e ciliate protists (Ricci et al., 1999) and fertilised eggs of the major Mediterranean herbivore, the sea urch<strong>in</strong> Paracentrotus lividus (Lamarck) (Pedrotti et al., 1996; Pesando et al., 1996; Pesando et al., 1998; Pesando et al., 1999). Additionally, adult P. lividus preferentially avoid graz<strong>in</strong>g on C. <strong>taxifolia</strong> (Lemée et al., 1993; Boudouresque et al., 1996; Lemée et al., 1996). This implies that these tox<strong>in</strong>s are active on eukaryotes and prokaryotes alike, and there is some evidence that they are toxic to angiosperm plants, <strong>in</strong>clud<strong>in</strong>g seagrasses (Guerriero et al., 1994). 2.2 CAULERPA TAXIFOLIA IN QUEENSLAND C. <strong>taxifolia</strong> has been recorded from the Queensland coast s<strong>in</strong>ce the 1850s and occurs from Cape York to the Gold Coast (Harvey, 1860; Cribb, 1958; Huisman, 2000; Phillips and Price, 2002). It has been recorded from south-east Queensland s<strong>in</strong>ce 1909, and from Moreton Bay s<strong>in</strong>ce 1950 which implies that it is most likely a native species (Phillips and Price, 2002; Qld Herbarium, 2002). Numerous genetic studies have suggested that the so-called <strong>in</strong>vasive “aquarium- Mediterranean” stra<strong>in</strong> of C. <strong>taxifolia</strong> orig<strong>in</strong>ated <strong>in</strong> Moreton Bay, us<strong>in</strong>g techniques such as allozyme surveys (Benzie et al., 2000), DNA f<strong>in</strong>gerpr<strong>in</strong>ts (Wiedenmann et al., 2001), ITS sequences (Jousson et al., 2000; Meusnier et al., 2001; Famà et al., 2002; Jane Thomas -4- Introduction
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