Mass mortality of diadematoid sea urchins in the Red Sea and Western Indian Ocean.

Sea urchins are primary herbivores on coral reefs, regulating algal biomass and facilitating coral settlement and growth.1,2,3,4,5,6,7,8,9,10,11,12 Recurring mass mortality events (MMEs) of Diadema species Gray, 1825 have been recorded globally,13,14,15,16,17,18,19,20,21,22,23 the most notorious and ecologically significant of which occurred in the Caribbean in 1983,14,17,19,20 contributing to the shift from coral to algal-dominated ecosystems.17,24,25 Recently, first evidence of Diadema setosum mass mortality was reported from the eastern Mediterranean Sea.23 Here, we report extensive mass mortalities of several diadematoid species inhabiting the Red Sea and Western Indian Ocean (WIO)26,27,28 including first evidence of mortalities in the genus Echinothrix Peters, 1853. Mortalities initiated in the Gulf of Aqaba on December 2022 and span the Red Sea, the Gulf of Oman, and the Western Indian Ocean (Réunion Island), with population declines reaching 100% at some sites. Infected individuals are characterized by spine loss and tissue necrosis, resulting in exposed skeletons (i.e., tests) and mortality. Molecular diagnostics of the 18S rRNA gene confirm the presence of a waterborne scuticociliate protozoan most closely related to Philaster apodigitiformis in infected specimens-identical to the pathogen found in the 2022 Caribbean mass mortality of Diadema antillarum.13,15,18 Collapse of these key benthic grazers in the Red Sea and Western Indian Ocean may lead to algal dominance over corals, threatening the stability of coral reefs on a regional scale.29,30,31,32 We issue a warning regarding the further expansion of mortalities and call for immediate monitoring and conservation efforts for these key ecological species.

Revisiting the species list of freshwater fish in Israel based on DNA barcoding.

Israel's region forms a continental bridge; hence, the freshwater fish fauna in Israel consists of unique populations of species that originated from Africa, Asia, or Europe and are often endemic or at the edge of their distribution range. Worldwide, fish biodiversity suffers significantly from pressures and disturbances of freshwater habitats, especially in arid regions, such as in parts of Israel. Biodiversity conservation requires efficient tools for monitoring changes in populations. DNA barcoding, by complementing and enhancing species identification, provides such monitoring tools. In this study, over 200 specimens representing over 28 species were DNA barcoded and together with previously available records, a DNA barcoding database for freshwater fish of Israel was established. Of the 71 distinct barcodes generated, 37% were new, attesting to the uniqueness of fish populations in Israel. For most species, morphological and molecular species identifications agreed. However, discrepancies were found for five genera. Based on DNA barcoding, we propose Acanthobrama telavivensis as a junior synonym for Acanthobrama lissneri. In Garra spp., we propose splitting Garra nana into two species and assigning Garra rufa in the region to Garra jordanica, or possibly to two species. Israeli Pseudophoxinus kervillei is not the same species as in Syria and Lebanon. However, Pseudophoxinus syriacus might not be endangered since it is genetically very similar to Pseudophoxinus drusensis. In Israel, instead of five reported Oxynoemacheilus species, combining DNA barcoding with morphology suggests only three. Genetic and geographic separation suggested that Aphanius mento is likely a species complex. The study provides a thorough barcoding database, suggests significant species reconsiderations in the region, and highlights the Sea of Galilee and the Beit She'an valley streams as biodiversity "hotspots." This study will therefore promote further studying of the fish species in the region and their ecology, as well as the monitoring and conservation of freshwater fish biodiversity in Israel and the region.