Poulin, E. | bioRxiv Science

bioRxiv2025

Skuas mortalities linked to positives HPAIV A/H5 beyond Polar Antarctic Circle

The ongoing extinction crisis, driven by human activity, poses a significant threat to seabirds and its especially relevant in highly valuable environments such as Antarctica. Among these threats, seabirds face the risk of local extinctions due to emerging infectious diseases like the Highly Pathogenic Avian Influenza Virus (HPAIV).Progressive spread of HPAIV A/H5N1 outbreaks across South America and the sub-Antarctic islands have been detected, reaching the northern regions of the West Antarctic Peninsula (WAP) during the 2023-2024 season. Here we conducted a comprehensive epidemiological survey conducted on sixteen seabird nesting localities along the WAP from November 2024 to January 2025 to assess the health status of the Antarctic seabirds and detect the presence of HPAIV. We observed unusual mortalities among nesting populations of skuas, with a total of 35 deaths skuas recorded along the WAP and beyond the Antarctic Polar Circle, including Important bird breeding areas around Margarita Bay. HPAIV A/H5 was confirmed in all dead skuas sampled (n=11), from six different locations. This finding represents the southernmost record of seabird mortality in Antarctica related to HPAIV to date. The expansion of HPAIV observed here raises concerns about further spread of avian flu out the Antarctic Peninsula, potentially leading to increased mortality rates in the Antarctic bird populations. These findings are relevant for the assessment of the general health status of Antarctic seabird populations and provide a baseline for the continuous monitoring of the HPAIV spread in avian species during the next breeding seasons.

ecology↗

bioRxiv2024

Highly Pathogenic Avian Influenza A (H5N1) Suspected in penguins and shags on the Antarctic Peninsula and West Antarctic Coast

Suspected cases of Highly Pathogenic Avian Influenza (H5N1) were detected in Adelie penguins and Antarctic shags at the southernmost latitude so far in Antarctica, at two breeding sites out of 13 visited, using highly specific PCR assay. These first records mark the progression of the H5N1 panzootic into Antarctica.

genetics↗

bioRxiv2023

Unveiling the co-phylogeny signal between plunderfish Harpagifer spp. and their gut microbiomes across the Southern Ocean.

Understanding the factors that sculpt fish gut microbiome is challenging, especially in natural populations characterized by high environmental and host genomic complexity. Yet, closely related hosts are valuable models for deciphering the contribution of host evolutionary history to microbiome assembly, through the underscoring of phylosymbiosis and co-phylogeny patterns. Here, we hypothesized that the recent allopatric speciation of Harpagifer across the Southern Ocean (1.2-0.8 Myr) will promote the detection of robust phylogenetic congruence between the host and its microbiome. We characterized the gut mucosa microbiome of 77 individuals from four field-collected species of the plunderfish Harpagifer (Teleostei, Notothenioidei), distributed across three biogeographic regions of the Southern Ocean. We found that seawater physicochemical properties, host phylogeny and geography collectively explained 35% of the variation in bacterial community composition in Harpagifer gut mucosa. The core microbiome of Harpagifer spp. gut mucosa was characterized by a low diversity, mostly driven by selective processes, and dominated by a single Aliivibrio taxon detected in more than 80% of the individuals. Almost half of the core microbiome taxa, including Aliivibrio, harbored co-phylogeny signal at microdiversity resolution with Harpagifer phylogeny. This suggests an intimate symbiotic relationship and a shared evolutionary history with Harpagifer. The robust phylosymbiosis signal emphasizes the relevance of the Harpagifer model to understanding the contribution of fish evolutionary history to the gut microbiome assembly. We propose that the recent allopatric speciation of Harpagifer across the Southern Ocean may have generated the diversification of Aliivibrio into patterns recapitulating the host phylogeny. ImportanceAlthough challenging to detect in wild populations, phylogenetic congruence between marine fish and its microbiome is critical, as it allows highlighting potential intimate associations between the hosts and ecologically relevant microbial symbionts. Through a natural system consisting of closely related fish species of the Southern Ocean, our study provides foundational information about the contribution of host evolutionary trajectory on gut microbiome assembly, that represents an important yet underappreciated driver of the global marine fish holobiont. Notably, we unveiled striking evidence of co-diversification between Harpagifer and its microbiome, demonstrating both phylosymbiosis of gut bacterial communities, and co-phylogeny of specific bacterial symbionts, in patterns that mirror the host diversification. Considering the increasing threats that fish species are facing in the Southern Ocean, understanding how the host evolutionary history could drive its microbial symbiont diversification represents a major challenge to better predict the consequences of environmental disturbances on microbiome and host fitness.

microbiology↗