Holmes Michael J, Lewis Richard J
Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072, Australia.
Toxins (Basel). 2025 Jul 30;17(8):380. doi: 10.3390/toxins17080380.
We adapt previously developed conceptual and numerical models of ciguateric food chains on the Great Barrier Reef, Australia, to model the bioaccumulation of ciguatoxins (CTXs) in parrotfish, the simplest food chain with only two trophic levels. Our model indicates that relatively low (1 cell/cm) densities of / species (hereafter collectively referred to as ) producing known concentrations of CTX are unlikely to be a risk of producing ciguateric fishes on the Great Barrier Reef unless CTX can accumulate and be retained in parrotfish over many months. Cell densities on turf algae equivalent to 10 /cm producing known maximum concentrations of Pacific-CTX-4 (0.6 pg P-CTX-4/cell) are more difficult to assess but could be a risk. This cell density may be a higher risk for parrotfish than we previously suggested for production of ciguateric groupers (third-trophic-level predators) since second-trophic-level fishes can accumulate CTX loads without the subsequent losses that occur between trophic levels. Our analysis suggests that the ratios of parrotfish length-to-area grazed and weight-to-area grazed scale differently (allometrically), where the area grazed is a proxy for the number of consumed and hence proportional to toxin accumulation. Such scaling can help explain fish size-toxicity relationships within and between trophic levels for ciguateric fishes. Our modelling reveals that CTX bioaccumulates but does not necessarily biomagnify in food chains, with the relative enrichment and depletion rates of CTX varying with fish size and/or trophic level through an interplay of local and regional food chain influences. Our numerical model for the bioaccumulation and transfer of CTX across food chains helps conceptualize the development of ciguateric fishes by comparing scenarios that reveal limiting steps in producing ciguateric fish and focuses attention on the relative contributions from each part of the food chain rather than only on single components, such as CTX production.
我们采用了之前在澳大利亚大堡礁开发的雪卡毒素食物链概念模型和数值模型，对鹦嘴鱼体内雪卡毒素（CTX）的生物累积进行建模，鹦嘴鱼所在的食物链最简单，只有两个营养级。我们的模型表明，产生已知浓度CTX的物种（以下统称为）相对较低的密度（1个细胞/平方厘米）不太可能导致大堡礁出现雪卡毒鱼，除非CTX能够在鹦嘴鱼体内累积并保留数月之久。与已知太平洋CTX - 4最大浓度（0.6皮克P - CTX - 4/细胞）相当的草皮藻细胞密度更难评估，但可能存在风险。这种细胞密度对鹦嘴鱼来说可能比我们之前认为的对雪卡毒石斑鱼（第三营养级捕食者）的风险更高，因为第二营养级的鱼类可以累积CTX负荷，而不会像营养级之间那样出现后续损失。我们的分析表明，鹦嘴鱼的体长与觅食面积之比以及体重与觅食面积之比的缩放方式不同（呈异速生长），其中觅食面积是所摄食数量的替代指标，因此与毒素累积成正比。这种缩放有助于解释雪卡毒鱼在营养级内部和之间的鱼体大小与毒性关系。我们的建模显示，CTX在食物链中会生物累积，但不一定会生物放大，CTX的相对富集和消耗速率会通过局部和区域食物链影响的相互作用，随鱼体大小和/或营养级而变化。我们的CTX在食物链中生物累积和转移的数值模型通过比较揭示雪卡毒鱼产生过程中限制步骤的情景，有助于概念化雪卡毒鱼的形成，并将注意力集中在食物链各部分的相对贡献上，而不仅仅是单个组成部分，如CTX的产生。
