Description of two new <i>Apseudopsis</i> species (<i>A. larnacensis</i> sp. nov and <i>A. salinus</i> sp. nov.) (Tanaidacea: Crustacea) from the Mediterranean and a biogeographic overview of the genus

The Mediterranean Sea is recognized as one of the most threatened marine environments due to pollution, the unintentional spread of invasive species, and habitat destruction. Understanding the biodiversity patterns within this sea is crucial for effective resource management and conservation planning. During a research cruise aimed at assessing biodiversity near desalination plants in the vicinity of Larnaca, Cyprus, conducted as part of the WATER-MINING project (Horizon 2020), specimens of the tanaidacean genus <i>Apseudopsis</i> were collected. These were classified into two species, identified as new to science, and are described herein as <i>Apseudopsis larnacensis</i> sp. nov and <i>Apseudopsis salinus</i> sp. nov. <i>Apseudopsis larnacensis</i> sp. nov is distinguished from its congeners by the presence of a lateral apophysis on pleonite 5, which is longer than those on pleonites 1-4, hyposphenia on pereonites 2-6, and six ventral spines on the propodus of pereopod 1. <i>Apseudopsis salinus</i> sp. nov. is characterized by a rounded posterolateral margin on pereonite 6, hyposphenia on pereonites 1-6, and four ventral spines on the propodus of pereopod 1. An updated key to the Atlantic and Mediterranean <i>Apseudopsis</i> species is provided. This study provides an overview of the distribution, bathymetric, and habitat preference of all known <i>Apseudopsis</i> species. Data extracted from the literature and two popular online databases were analyzed to identify diversity patterns across seas and ecoregions. Our analysis reveals that the Mediterranean is the most diverse region for <i>Apseudopsis</i>, with the Levantine Sea hosting ten species and the South European Atlantic Shelf seven species. Shallow waters and muddy and sandy habitats are conducive for <i>Apseudopsis</i> occurrence.