Capacity of deep‐sea corals to obtain nutrition from cold seeps aligned with microbiome reorganization

Cold seeps in the deep sea harbor various animals that have adapted to utilize seepage chemicals with the aid of chemosynthetic microbes that serve as primary producers. Corals are among the animals that live near seep habitats and yet, there is a lack of evidence that corals gain benefits and/or incur costs from cold seeps. Here, we focused on Callogorgia delta and Paramuricea sp. type B3 that live near and far from visual signs of currently active seepage at five sites in the deep Gulf of Mexico. We tested whether these corals rely on chemosynthetically-derived food in seep habitats and how the proximity to cold seeps may influence; (i) coral colony traits (i.e., health status, growth rate, regrowth after sampling, and branch loss) and associated epifauna, (ii) associated microbiome, and (iii) host transcriptomes. Stable isotope data showed that many coral colonies utilized chemosynthetically derived food, but the feeding strategy differed by coral species. The microbiome composition of C. delta, unlike Paramuricea sp., varied significantly between seep and non-seep colonies and both coral species were associated with various sulfur-oxidizing bacteria (SUP05). Interestingly, the relative abundances of SUP05 varied among seep and non-seep colonies and were strongly correlated with carbon and nitrogen stable isotope values. In contrast, the proximity to cold seeps did not have a measurable effect on gene expression, colony traits, or associated epifauna in coral species. Our work provides the first evidence that some corals may gain benefits from living near cold seeps with apparently limited costs to the colonies. Cold seeps provide not only hard substrate but also food to cold-water corals. Furthermore, restructuring of the microbiome communities (particularly SUP05) is likely the key adaptive process to aid corals in utilizing seepage-derived carbon. This highlights that those deep-sea corals may upregulate particular microbial symbiont communities to cope with environmental gradients

Juvenile corals inherit mutations acquired during the parents lifespan

128 years ago, August Weismann proposed that the only source of inherited genetic variation in animals is the germline. Julian Huxley reasoned that if this were true, it would falsify Jean-Baptiste Lamarck′s theory that acquired characteristics are heritable. Since then, scientists have discovered that not all animals segregate germline cells from somatic cells permanently and early in development. In fact, throughout their lives, Cnidaria and Porifera maintain primordial stem cells that continuously give rise to both germline and somatic cells. The fate of mutations generated in this primordial stem cell line during adulthood remains an open question. It was unknown whether post−embryonic mutations could be heritable in animals−until now. Here we use two independent genetic marker analyses to show that post-embryonic mutations are inherited in the coral Acropora palmata (Cnidaria, Anthozoa). This discovery upends the long-held supposition that post-embryonic genetic mutations acquired over an animal′s lifetime in non-germline tissues are not heritable2. Over the centuries-long lifespan of a coral, the inheritance of post-embryonic mutations may not only change allele frequencies in the local larval pool but may also spread novel alleles across great distances via larval dispersal. Thus, corals may have the potential to adapt to changing environments via heritable somatic mutations. This mechanism challenges our understanding of animal adaptation and prompts a deeper examination of both the process of germline determination in clonal animals and the role of post−embryonic genetic mutations in adaptation and epigenetics. Understanding the role of post−embryonic mutations in animal adaptation will be crucial as ecological change accelerates in the Anthropocene

Discovery of active off-axis hydrothermal vents at 9° 54'N East Pacific Rise

International audienceWe describe the discovery of a large, active, high-temperature off-axis hydrothermal vent field on the East Pacific Rise. Hydrothermal vents are more prevalent across the crestal region of midocean ridges than previously thought. Our finding has important implications for understanding the fundamental controls on vent location and hydrology of hydrothermal systems along the crest of fast-spreading midocean ridges. The site provides a validation point for observations and models that call for significant hydrothermal heat loss beyond the immediate spreading axis. Finding an active off-axis vent field implies that temporally stable off-axis vent-endemic populations may provide a source of colonizing fauna to on-axis hydrothermal ecosystems after seafloor volcanic eruptions