Microbiota in fungal-infected sea turtle nest

Hatchery practices influence the outcome of conservation success. In sea turtle hatchery, reusing sand is believed to associate with microbe or pathogen accumulation which affects hatching success. It is unclear whether such approach increases the risk of Fusarium solani species complex (FSSC) infection, which caused huge mortality in sea turtle eggs worldwide. We employed 16S and ITS amplicon sequencing in 123 nest sand samples and isolated fungal strains from diseased eggshells across seven hatcheries in Malaysia. FSSC was isolated from all sampled hatcheries which F. falciforme was the predominant species. A distinct microbial composition and higher abundance of FSSC (mean 5.2 %) were found in used-sand of hatchery. Furthermore, we revealed another fungus Pseudallescheria boydii consistently appeared in higher abundance (mean 11.4 %) in FSSC-infected nest and associated with lower hatching success. An apparent exception was found in one hatchery that maintains more stringent practice by changing the hatchery location (i.e. sand) every nesting season. The microbiota of nest sand from this hatchery is similar to natural environment. Moreover, the FSSC abundance of this hatchery was also the lowest when compared to other sites. This study may help suggest practices that reduce fungal infection on turtle eggs in hatchery setting.

海龟孵化场的运营实践直接影响保护工作的最终成效。在海龟孵化场中，重复使用沙砾被认为会引发微生物与病原体积累，进而干扰海龟卵的孵化成功率。目前尚不清楚这种操作是否会提升茄病镰孢菌种复合体（Fusarium solani species complex, FSSC）的感染风险——该复合体已在全球范围内造成大量海龟卵死亡。本研究针对马来西亚7个孵化场的123份巢沙样本开展16S与ITS扩增子测序，并从患病卵壳中分离得到真菌菌株。所有采样孵化场均分离出了FSSC，其中镰状镰孢（Fusarium falciforme）为优势菌种。经检测，孵化场的重复使用沙砾中存在独特的微生物群落组成，且FSSC的丰度更高（平均占比5.2%）。此外，我们还发现另一真菌——波氏假阿利什霉（Pseudallescheria boydii）在感染FSSC的巢穴中持续维持较高丰度（平均占比11.4%），且与更低的孵化成功率显著相关。但有一个孵化场呈现出明显例外：该场执行了更为严格的操作规范，在每个繁殖季都会更换孵化场地的沙砾。该孵化场的巢沙微生物群落组成与自然环境高度相似，且其FSSC丰度也是所有采样点中最低的。本研究可为孵化场环境下降低海龟卵真菌感染风险的实践方案提供有益参考。