Marine Platyhelminthes of the Maldives: A Review of Their Diversity and Distribution

The phylum Platyhelminthes is poorly studied in the Republic of Maldives, and its biodiversity remains largely undocumented. By integrating published literature, citizen-science platforms, and online photographic resources, 39 species belonging to 20 genera and nine families were compiled, including both free-living and parasitic taxa. Only a limited fraction of records came from the formal literature, whereas most were retrieved from citizen-science and web-based sources, highlighting the contribution of non-traditional data streams to biodiversity assessment. Analysis of 170 occurrence records showed a marked spatial unevenness, with most observations concentrated in the central and northern atolls, a pattern likely driven by differences in survey effort, tourism, and diving activity rather than by true biogeographic variation. Free-living species were mainly represented by conspicuous pseudocerotids, while parasitic flatworms were underrepresented because they require host-targeted sampling and are difficult to detect through photographic surveys. Overall, the review shows that current knowledge of Maldivian flatworm diversity is fragmentary and probably underestimated. Beyond compiling existing records, it establishes a baseline for future research on flatworm biodiversity in the Maldives, including systematic sampling, integrative taxonomy, and DNA barcoding, which will be essential to improve species identification, reveal hidden diversity, and support future conservation and management efforts.