A global DNA barcode reference library for Solenogastres (Mollusca, Aplacophora)

Solenogastres (Mollusca, Aplacophora) are shell-less, vermiform marine molluscs found across a wide range of marine habitats and depths. Despite their broad distribution, their diversity remains poorly documented. Because Solenogastres tend to be externally cryptic, morphological identification requires trained specialists and time-consuming processes (e.g., histology). DNA barcoding has emerged as a powerful tool to complement traditional taxonomy, yet Solenogastres remain underrepresented in public genetic datasets. Here, we present the first global DNA barcode reference library for Solenogastres, comprising 655 newly generated sequences combined with previously published sequences, resulting in 531 COI, 483 16S, and 129 CytB barcodes representing an estimated 325 aplacophoran species (287 solenogaster species) from 642 specimens. The included taxa broadly encompass the diversity and geographic distribution of the group. Specimen identification was achieved through an integrative approach that combined molecular data with morphological information from histology, light microscopy, and scanning electron microscopy. Phylogenetic analysis of the concatenated dataset recovers major clades consistent with transcriptome-based studies and reveals several lineages that may require taxonomic revision. This curated dataset, available on GenBank, provides an essential resource for future efforts in systematics, ecology, and biodiversity research of Solenogastres.