Biology subjects

del Rio-Hortega, L.

Publications and source records attributed to del Rio-Hortega, L..

3 recordsLinked to original sources

bioRxiv2026

Diversity, host-specificity, and environmental drivers of the coral reef eukaryome

Coral reefs are among the most diverse ecosystems on Earth, yet the diversity and structure of their associated microeukaryotic communities remain poorly resolved. We characterized reef-associated eukaryomes across 113 reefs spanning the Pacific Ocean using more than 6,300 samples from corals, seawater, and sediments during the Tara Pacific expedition. We identified [~]121,000 eukaryotic ASVs, revealing one of Earths largest undocumented reservoirs of eukaryotic diversity; over 80% of the recovered diversity was previously undetected in global ocean surveys and fewer than 2% of sequences matched reference databases. Reef habitats supported highly distinct communities, with sediments and seawater harboring 20-40-fold higher richness than corals. Unexpectedly, coral-associated communities across 29 host lineages were consistently dominated by small metazoans, particularly demosponges and maxillopods, identifying these taxa as pervasive and previously unrecognized components of coral eukaryomes alongside Apicomplexa. Across the Pacific, eukaryome composition was strongly structured by environmental gradients, with thermal stress emerging as the primary driver of community turnover. Together, these results identify coral reefs as a globally important reservoir of hidden eukaryotic diversity and reveal the reef eukaryome as a sensitive indicator of ecosystem reorganization under climate change.

systems biology↗

bioRxiv2026

HIDDEN APICOMPLEXAN PARASITE DIVERSITY LINKS CORAL AND PLANKTON MICROBIOMES ACROSS REEF SEASCAPES

Parasitism is one of the most widespread trophic strategies in nature, though its diversity and ecological distribution in marine ecosystems remain poorly characterized. Apicomplexa are a major clade of obligate parasites best known for medically important taxa, yet their diversity and distribution in the ocean is still largely unresolved. Here, we used metabarcoding data from the Tara expeditions to investigate the diversity, distribution, and environmental drivers of Apicomplexa across coral reef ecosystems and adjacent oceanic habitats. By integrating samples spanning planktonic communities, coral tissues, and marine sediments across multiple oceanic regions, we substantially expand the known phylogenetic breadth of marine apicomplexans. Although apicomplexans were generally low in relative abundance, they were widely distributed across marine environments. Community composition differed markedly among habitats. Corallicolid lineages were consistently associated with coral hosts, whereas planktonic samples harbored a greater diversity of apicomplexans, dominated by crustacean-associated gregarines. Sediments contained particularly high apicomplexan richness, including several poorly characterized groups. Capitalizing on the pan-Pacific transect of the expedition, we resolved biogeographic patterns in apicomplexan diversity across ocean basins: tropical regions showed the highest overall diversity, while polar environments contained distinct apicomplexan assemblages not detected in other ocean biomes. Together, these results highlight the extensive and previously underappreciated diversity of marine Apicomplexa and demonstrate that integrating multiple marine biomes is essential for resolving the phylogenetic and ecological breadth of parasitism in the ocean.

genomics↗

bioRxiv2026

Ocean-scale transcriptomic analysis of corallicolids (Apicomplexa) reveals their ubiquity and molecular interactions with Pocillopora corals.

Corals are complex holobionts, encompassing numerous prokaryotes, viruses, and protists. This associated microbial community strongly influences coral health and its resilience to global ocean warming. Corallicolid apicomplexans are widespread coral-infecting parasites, yet their impact on the coral host remains poorly understood. This knowledge gap largely stems from the low abundance of these parasites in coral tissues, which makes them difficult to isolate and access to their genetic material. Here we analyzed nearly 1,000 Pocillopora coral colonies collected from 32 islands during the Tara Pacific expedition to identify the drivers of corallicolid prevalence and abundance. Corallicolids were detected in almost all Pocillopora colonies with variable relative abundances between islands. The high abundance of specific corallicolid populations correlates with seawater temperature and levels of host protein carbonylation. We used a large collection of 297 metatranscriptomes to assemble a corallicolid transcriptome and we identified apicomplexan parasite signature genes, including the GRA9 and PV2 confirming the close phylogenetic relationship with the family of Eimeriidae. Gene expression patterns indicate that the high abundance of corallicolids correlates with a high transcription of genes encoding apical complex proteins and genes involved in the control of host immune defenses. Overall, this study provides new insights into corallicolid biology and its interaction with the coral host by combining a newly generated transcriptome with a large-scale sampling of Pocillopora corals across the Pacific Ocean.

genomics↗