The present paper reports the water mite identified as Litarachna duboscqi collected in March 2024 from nautical ropes in the harbour of Trapani (Sicily). It is the first record for southern Italy and the central Mediterranean Sea.

A female copepod specimen belonging to the family Botryllophilidae Sars G.O., 1921 was retrieved for the first time in December 2023 from nautical ropes of the tourist marina in Palermo (Cala Marina), near the commercial port of the city. The individual lacks many of the distinctive morpho-anatomical characteristics of the class Copepoda, as usual in cyclopoid parasites. In this group, females typically carry paired multiseriate egg sacs, which are extruded from the genital openings and lead to taxonomic identification. The family is commonly associated with tunicates. There are few reports of commensal and/or parasitic copepods associated with sea squirts in the Mediterranean Sea. This record cannot be treated as a new non-indigenous species for the Italian coasts yet, as there are no extensive studies on the distribution of the taxon.

This preliminary study presents an updated checklist of amphipod crustaceans inhabiting Italian seas and provides valuable insights into their diversity, distribution, and ecological traits. By combining existing literature with unpublished data, we were able to record 500 species in Italian waters. The analyses revealed a significant increase in the number of amphipod species documented in the Country, primarily due to intensified research efforts and the introduction of non-native species. This study highlights the importance of ongoing monitoring and research to assess marine biodiversity. Future efforts should prioritize understudied groups, such as planktonic species, and those living in deep-sea marine environments.

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 However, incomplete or outdated information on species distributions has often led to misidentifications and inconsistencies in literature, highlighting the need for updated and reliable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.

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 10,700 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 the 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.

We classified European and adjacent seas into nine biogeographic realms and provinces (bioregions) based on a new compilation of over 17,000 records of the distribution of 1,182 native species of Amphipoda (Crustacea) at a spatial resolution of 4° latitude longitude. The dominant, characterising, and percent of unique species (endemicity) for each realm are reported. In order of distinctiveness and endemicity the bioregions were the Mid-North Atlantic (53 %), Black Sea freshwater (35 %), Mediterranean and Black Sea marine (32 %), Canary Islands and Cape Verde (21 %), North-West coast of Africa (14 %), North-East Atlantic shelf (12 %), coastal Norwegian Sea (9 %), Azores (9 %) and Baltic Sea (6 %). A hierarchical cluster analysis suggested these may be grouped into realms and provinces. Records filling geographic gaps, and comparable studies on additional taxa, will improve this biogeographic analysis. Meanwhile, the planning of Marine Protected Areas needs to include areas within each of these bioregions to be inclusive of all species in the study area.