Species distribution data are essential for understanding biodiversity patterns, supporting conservation planning and assessing the impacts of environmental change. Amphipods represent one of the most abundant and diverse groups of marine macroinvertebrates, encompassing over 10,900 species worldwide and exhibiting a wide range of trophic and ecological roles. Owing to their sensitivity to environmental changes, amphipods are widely used as bioindicators and are of considerable interest in both basic and applied research. However, incomplete or outdated information on species distributions has often led to misidentifications and inconsistencies in literature, highlighting the need for updated and reliable checklists.

This study presents an inventory of unpublished records comprising more than 300 species collected from the Italian maritime zones of the Adriatic, Tyrrhenian and Ionian areas. The Tyrrhenian Sea exhibited the highest taxonomic richness, whereas the Adriatic Sea accounted for the greatest number of records, likely reflecting differences in sampling effort. Eleven non-indigenous species (NIS), representing 3.6% of the total, were recorded, primarily in ports, lagoons and aquaculture facilities, while 6.6% of the species were classified as cryptogenic or of uncertain origin. Sandy and mixed substrates supported the highest species richness, consistent with their greater sampling effort. Overall, this study provides an updated overview of amphipod biodiversity and distribution in Italian seas and underscores the need for systematic and continuous monitoring. According to the FAIR (Findable, Accessible, Interoperable, Reusable) principles, the dataset was published on the GBIF (Global Biodiversity Information Facility) platform.

Amphipoda, Italian waters, Mediterranean Sea, biodiversity assessment, NBFC, GBIF-IT, LifeWatch-IT