Carletti Marilyn, Viñuela Rodríguez Nuria, Rossetti Gaia, Rossi Virginia, Tan Bryan Gabriel Pulido, Reimer James Davis
Molecular Invertebrate Systematics and Ecology Lab, Graduate School of Engineering and Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
Marche Polytechnic University, Ancona, Italy.
PeerJ. 2025 Jul 30;13:e19757. doi: 10.7717/peerj.19757. eCollection 2025.
Nematodes are among the most diverse and abundant metazoans in aquatic habitats, contributing significantly to global biodiversity. Despite their abundance and importance, the presumed number of undescribed species is high and their diversity is often underestimated.
In this research, sediment samples were collected from three microhabitats (bare sand, seagrass, coral) in two sites around Okinawa-jima Island in subtropical southern Japan. Nematode specimens were obtained by filtering the sediment and were then used to determine meiofaunal assemblages with morphology and molecular methods at the two sites and to compare them with environmental variables.
The results showed an overwhelmingly high biodiversity of nematofauna with both methods. The morphological identification of free-living nematodes was partly supported by molecular analyses, with the results varying more regarding less common taxa. The discrepancies between different methods may be due to low success of DNA amplifications, high nucleotide variability, and overestimation of congeneric specimens. We observed that coral reef habitats clearly differed from nearby sand and seagrass beds in terms of nematode genus-level assemblages. We identified at least 10 orders and 38 genera of nematodes from our samples that only span two different sites, and it is highly likely these samples include undescribed taxa. Our results strongly suggest that coral reefs and neighboring areas are hot-spots for nematode diversity, at least around Okinawa-jima Island if not also in other coral reef regions.
线虫是水生栖息地中种类最多、数量最丰富的后生动物之一，对全球生物多样性有重大贡献。尽管它们数量众多且很重要，但未描述物种的推测数量很高，其多样性常常被低估。
在本研究中，从日本亚热带南部冲绳岛周围两个地点的三个微生境（裸沙、海草、珊瑚）采集沉积物样本。通过过滤沉积物获得线虫标本，然后用形态学和分子方法确定这两个地点的小型底栖动物群落，并将其与环境变量进行比较。
两种方法的结果均显示线虫动物群具有极高的生物多样性。分子分析部分支持了对自由生活线虫的形态学鉴定，对于不太常见的分类群，结果差异更大。不同方法之间的差异可能是由于DNA扩增成功率低、核苷酸变异性高以及对同属标本的高估。我们观察到，就线虫属级群落而言，珊瑚礁栖息地明显不同于附近的沙地和海草床。我们从样本中鉴定出至少10个目和38个属的线虫，这些样本仅来自两个不同地点，很有可能这些样本包含未描述的分类群。我们的结果有力地表明，珊瑚礁及其邻近区域是线虫多样性的热点地区，至少在冲绳岛周围如此，即便在其他珊瑚礁区域并非也是如此。
