Global distribution of Calyptospadix cerulea Clarke, 1882 under various synonyms (A), with an inset showing its distribution in the Baltic Sea (B). The star symbol in the inset marks the C. cerulea record documented in the present study at the Torpedo Launch Station in the Gulf of Gdańsk. Occurrence records were downloaded from GBIF.org (2025), OBIS, Nemesis database and earlier taxonomic works (for detailed list see Suppl. material 2).