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.

Abiotic conditions influence biodiversity and population connectivity, the assessment of which is critical for predicting climate change impacts and guiding conservation efforts. Coral reefs face severe losses, making effective conservation strategies increasingly urgent. Here, we use a seascape genomics approach to examine the population genetic structure of three non-model scleractinian corals around the Arabian Peninsula, a region with distinctive oceanographic features. We reveal contrasting patterns across species, which we integrate with geographic distances, larval dispersal models, and environmental data. Population structure appears shaped both by isolation by distance (IBD) and isolation by resistance (IBR), with environmental gradients often covarying with spatial separation. Our findings clarify coral diversification and evolutionary responses to conditions around the region. This work also provides a methodological framework to advance our understanding of processes structuring reef populations, thereby informing efforts to design robust marine protected area networks in the face of climate change and biodiversity loss.

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.