ABSTRACT

Sea turtles harbour epizoic diatoms of which several taxa are considered exclusively epizoic and possible ‘commensals’. The epizoic diatom communities were examined from 124 individuals representing four turtle species (Chelonia mydas, Eretmochelys imbricata, Lepidochelys olivacea and Dermochelys coriacea), from three well-defined areas: Eastern Caribbean, Equatorial West Atlantic and South Pacific. Overall, the epizoic diatoms are very small and need electron microscopy to be accurately identified. Non-Metric MultiDimensional Scaling analyses permitted us to evaluate these diatom assemblages according to turtle species and biogeography. Differentiation was mainly driven by 14 taxa in the diatom genera Chelonicola, Tripterion, Tursiocola, Olifantiella, Navicula and Achnanthes. The highest diatom species richness was found associated with E. imbricata. Dermochelys coriacea and L. olivacea exhibit lower diatom diversities. Some difference in colonization was detected between C. mydas adults and juveniles at the same site, with higher diatom diversity for the juveniles. Within C. mydas we show geographic differentiation of their diatom assemblages, particularly between populations of the Equatorial West Atlantic and South Pacific. Two Tursiocola species ‘commensal’ to C. mydas seemed to be geographically restricted to French Guiana and the Caribbean. Dermochelys coriacea has a diatom assemblage very different from those of the three other turtles, probably due to its particular behaviour. Lepidochelys olivacea is also unique in the complete lack of Chelonicola species. Based on our results, the diatoms Tripterion societatis and Chelonicola spp. (as currently defined) appear to be mutually exclusive on turtle hosts. This study adds significantly to our understanding of the global distribution of epizoic diatoms on sea turtles. We discuss to what extent these diatoms can be used as a geographic marker with regard to the biogeography of the diatoms themselves and their host.

摘要

海龟拥有流行性硅藻，其中一些分类群被认为是完全流行的并且可能是“共生体”。从代表四个龟类（海龟、Eretmochelys imbricata、Lepidochelys olivacea和Dermochelys coriacea）的124 个个体中检查了生代硅藻群落，这些个体来自三个明确定义的区域：东加勒比海、赤道西大西洋和​​南太平洋。总体而言，生代硅藻非常小，需要电子显微镜才能准确识别。非度量多维缩放分析使我们能够根据海龟物种和生物地理学评估这些硅藻组合。分化主要由硅藻属Chelonicola、Tripterion、Tursiocola、Olifantiella、Navicula 中的14 个分类群驱动和阿克南特斯。发现最高的硅藻物种丰富度与E. imbricata相关。Dermochelys coriacea和L. olivacea表现出较低的硅藻多样性。在同一地点的C. mydas成虫和幼虫之间检测到一些定植差异，幼虫的硅藻多样性更高。在C. mydas 中，我们展示了它们的硅藻组合的地理差异，特别是在赤道西大西洋和​​南太平洋的种群之间。与C. mydas “共生”的两种Tursiocola物种似乎在地理上仅限于法属圭亚那和加勒比地区。皮甲藻可能是由于其特殊的行为，它的硅藻组合与其他三只海龟的硅藻组合非常不同。Lepidochelys olivacea在完全缺乏Chelonicola物种的情况下也是独一无二的。根据我们的结果，硅藻Tripterion societatis和Chelonicola spp。（如当前定义）在海龟宿主上似乎是互斥的。这项研究大大增加了我们对海龟上生代硅藻全球分布的理解。我们讨论了这些硅藻在多大程度上可以用作硅藻本身及其宿主生物地理学的地理标记。