Federica Barreca

Earth's biodiversity is central to ecosystem health and resilience, providing essential functions and services. The Red Sea is a recognised marine biodiversity hotspot with high endemism and unique environmental conditions that support extensive but poorly resolved biodiversity. Here, we applied metagenomic analyses to sediment samples collected from coastal to deep‐sea environments during the Red Sea Decade Expedition 2022 to characterise biodiversity across the web of life. From a single shotgun assay per sample, this approach simultaneously characterised the sediment microbiome, which amplicon‐based surveys recover only through parallel, targeted assays, and extended detection to higher eukaryotes. Using high‐throughput sequencing, we generated 12.8 billion sequences, revealing taxa covering all domains of life. Although eukaryotic sequences represented only 0.7% of the taxonomically annotated dataset, we managed to identify 679 eukaryotic families. Prokaryotic diversity was high, as expected in a basin‐scale sampling coupled with high sequencing depth, with groups covering a wide functional array. Community structure analyses revealed depth‐driven stratification of open‐ocean benthic microbial communities and latitudinal structuring of coastal benthic eukaryotes. Overall, this dataset provides an empirical reliability–coverage trade‐off with direct consequences for the design of eDNA monitoring programmes targeting conservation‐priority taxa, and clear priorities for taxa specific reference‐database expansion.

Antipathidae Ehrenberg, 1834 is the largest family within the order Antipatharia (commonly known as black corals), and includes corals distributed worldwide from shallow to deep waters. With over 124 nominal species, Antipathidae comprises taxa with diverse morphologies, whose taxonomic boundaries, diversity, and distribution remain poorly resolved due to morphological convergence, limited sampling, and discordance between genetic and morphological evidence. Here, we integrated phylogenomic analyses from target-capture of ultraconserved elements (UCEs) and exon loci with detailed morphological analyses for a total of 107 black coral specimens, including 70 collected from the Red Sea between 3 and 623 m water depth, 18 from the Indo-Pacific and Atlantic Oceans between 3 and 26 m water depth, and 19 specimens from museum collections, five of which representing type material. Moreover, previously published UCE data from 77 specimens was included in the analysis. Our results supported the resurrection of the family Stichopathidae Roule, 1905 to accommodate the genera Cirrhipathes de Blainville, 1830 and Stichopathes Brook, 1889, formerly assigned to Antipathidae. We described three new genera, Multilobopathes gen. nov., Papillopathes gen. nov., and Opreskopathes gen. nov., to accommodate species previously assigned to Antipathes Pallas, 1766, including newly discovered taxa from the Red Sea. Antipathes lentipinna is reassigned to Multilobopathes lentipinna (Brook, 1889) comb. nov., Antipathes grandis to Papillopathes grandis (Verrill, 1928) comb. nov., Antipathes caribbeana, Antipathes umbratica, and Antipathes rubusiformis are reassigned to Opreskopathes caribbeana (Opresko, 1996), Opreskopathes umbratica (Opresko, 1996), and Opreskopathes rubusiformis (Warner & Opresko, 2004) comb. nov., respectively. Finally, four new species, Multilobopathes ornatus sp. nov., Multilobopathes intricatus sp. nov., Multilobopathes densispinosus sp. nov., and Stichopathes arenicola sp. nov., are described from the Red Sea. Our results provide the first step towards a comprehensive revision of the diversity and distribution of the order Antipatharia.

Colonial corals display diverse growth forms shaped by both environmental conditions and intrinsic developmental mechanisms. Understanding these internal morphogenetic rules is critical for accurately modeling coral colony formation. In this study, we investigated the intrinsic budding patterns of Dendrophyllia cf. horsti , an azooxanthellate deep-sea coral from the Red Sea. Using detailed morphological analyses of colony architecture, we identified consistent intrinsic constraints that govern colony development. Lateral corallites bud at a consistent angle (mean 15.9°) relative to the growth axis, and the orientation of the directive septa in daughter corallites remains stable across generations (mean 19.8°). Budding was consistently restricted to two specific sites per internode located near the lateral primary septa. In most colonies, budding occurred on the same side at successive internodes, although occasional observations suggested variation in the relative position of budding sites. These findings suggest that even in deep-sea, non-photosynthetic species, colony morphology is strongly regulated by intrinsic developmental constraints, as previously demonstrated in congeneric species. The results contribute valuable data for simulating coral growth and highlight the importance of intrinsic constraints in shaping colonial forms across Scleractinia.

Two species of squat lobsters from the families Munididae and Chirostylidae were collected by ROV and manned submersible, respectively, at mesophotic depths of the Red Sea off the coast of Saudi Arabia. Sadayoshia benzoniae sp. nov. is described based on two specimens found among coral rubble and octocorals collected at depths of 104–248.5 m, whereas Uroptychus deliquus Baba, Corbari & Macpherson, 2024 is reported from the Red Sea for the first time, based on a single specimen found in association with a fan coral, Melithaea sp. (Alcyonacea, Melithaeidae), at a depth of 220 m. Both genera are recorded from the Red Sea for the first time.

The diversity and evolution of the Red Sea invertebrates in mesophotic and deep-water benthic ecosystems remain largely unexplored. The Palaemonidae is a diversified family of caridean shrimps with numerous taxa in need of taxonomic revisions based on recent molecular analyses. The Red Sea mesophotic and bathyal palaemonid shrimps are largely unstudied. During recent expeditions off the Red Sea coast of Saudi Arabia, several palaemonid specimens were collected at a depth range of 88–494 m, spanning the mesophotic and bathyal zones. This material was examined morphologically and genetically to infer phylogenetic relationships among the Red Sea taxa and several other palaemonid genera. The concordant morphological and genetic data led to the description of two new genera and two new species. Moreover, one species was recorded in the Red Sea for the first time, with a new host record, whereas three further deep-water species, which do not occur in the Red Sea, were formally transferred to a different genus. As more exploration efforts are deployed, research on the diversity and evolutionary relationships among marine invertebrates from the Red Sea will further underline the uniqueness of its mesophotic and bathyal fauna.