Fig 1.
The mechanism of bioaccumulation of CTXs.
Gambierdiscus (for example G. polynesiensis CG14 (A)) at the base of the food web inhabiting the macroalgae Padina spp. (B) [1]. A herbivore, here a white trevally (Pseudocaranx dentex) (C) [2] consumes CTX from G. polynesiensis along with the macroalgae, which then either passes directly to humans through consumption, or through an intermediary piscivorous vector such as Australian spotted mackerel (Scomberomorus munroi) (D) [3]. As an example, the red portion of the humans at the top of the food chain representing the 37.8% of the population in New Caledonia contracting ciguatera during their lifetime [4]. Image of G. polynesiensis (strain CG15) taken by A. L. Kretzschmar, 2016, Nikon Eclipse TS100 equipped with an Infinite Luminera 1 camera.
Table 1.
Published qPCR assays for Gambierdiscus and Fukoyoa spp.
Table 2.
Cases of CFP reported to health authorities in Queensland, Australia.
Table 3.
List of Gambierdiscus clonal strains used for the qPCR assay.
Table 4.
G. lapillus specific qPCR primer set for 138bp amplicon from the SSU rRNA designed in this study.
Fig 2.
(A) Map of Australia, with the position of Heron Island (red circle); (B) Heron Island including surrounding reefs (dotted lines); (C) Approximate location of sampling sites around Heron Island. Map adapted from Kretzschmar et al. (2017) [21] and edited in the GNU Image Manipulation Program 2.8 (http://gimp.org).
Table 5.
Cross-reactivity of the qPCR primer set.
Fig 3.
qPCR cell based standard curves of G. lapillus strains.
HG4 (circle) and HG7 (triangle). Error bars represent the deviation of technical replicates during reactions; x-axis is log scale.
Fig 4.
qPCR gene based standard curves of G. lapillus.
Error bars represent the deviation of technical replicates during reactions; x-axis is log scale.
Fig 5.
G. lapillus presence at the macroalgal sampling sites around Heron Island.
The spatial replicates for each site are set up as shown in (A); the sites in (B) linked to numbering in Fig 2 where positive (green) and negative (purple) as per S1 Table.
Fig 6.
Detection of G. lapillus per spatial replicate at each macroalgal sampling site.
Cell numbers were normalised to the HG7 standard curve (Fig 3A). Also shown are the spatial replicates per macroalgal substrate where Chnoospora sp. samples are represented by circles, Padina sp. by squares and Sargassum sp. by crosses (S1 Table).