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Our knowledge regarding the role of the microbiome in fish health has been steadily increasing in the last decade, especially for species of commercial interest. Conversely, relatively few studies focus on the microbiomes of wild fish, especially apex predators like sharks, due to lower economic interest and greater difficulty in obtaining samples. Studies investigating microbiome differences between diverse anatomical locations of sharks are limited, and the majority of the available studies are focused on the microbial diversity present on shark teeth, with the aim of preventing infections due to bites of these animals or evaluating the presence of certain pathogens in healthy or diseased specimens. Here, we investigated the skin, mouth, gills, and cloaca microbiomes of five individuals of two phylogenetically distant species of sharks (Prionace glauca and Somniosus rostratus) to obtain a better understanding of the diversity regarding the microbiomes of these animals, how they change throughout different body parts, and how much they are influenced and determined by the ecology and evolutionary relationship between host and microbiome. To confirm the taxonomy of the sharks under study, we barcoded the specimens by sequencing the mtDNA COI from a biopsy of their skin. Microbial diversity based on the 16S rRNA gene reveals that partially overlapping microbiomes inhabit different body parts of each shark species, while the communities are distinct between the two species. Our results suggest that sharks' microbiome species-specific differences are controlled by the ecology of the shark species. This is the first study comparatively analyzing the microbiome diversity of different anatomical locations in two shark species of the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

As human exploration and harvesting moves to the high seas, ecological understanding of the deep sea has become a priority, especially in those commercially exploited species whose life cycle, habitat use, and demographic structure remain poorly understood. Here we combine otolith trace element and stable isotope analyses with microsatellite data to investigate population structure and connectivity in the migratory deep-sea black scabbardfish (Aphanopus carbo), sampled along a latitudinal gradient spanning much of the known species range in the Northeast Atlantic. In each sampled life stage, otolith trace element and oxygen isotope compositions are similar among fish from different capture locations, but otolith compositions vary greatly between life stages. Oxygen isotope compositions indicate ontogenetic migrations from relatively warm water conditions during larval growth to cooler waters with increasing age. Analysis of microsatellite DNA also suggests lack of genetic structure among the areas sampled. The multidisciplinary approach employed collectively suggests that A. carbo individuals undergo an ocean-scale ontogenetic migration, beginning with spawning in southern, warm-water Macaronesian areas (potentially dominated by Madeira), followed by a large proportion of immature fish moving to and feeding on the continental slope in northern areas. The results lend the first conclusive evidence for defining the life-history circuit of this species and the perception of its stock structure across the North Atlantic. L'exploration humaine vers la haute mer et l'exploitation de cette derniere font en sorte que la comprehension ecologique des profondeurs marines devient prioritaire, particulierement en ce qui concerne les especes exploitees a des fins commerciales dont les cycles biologiques, les habitudes d'utilisation de l'habitat et les structures demographiques demeurent mal compris. Nous combinons l'analyse des elements en traces et des isotopes stables des otolites a des donnees de microsatellites pour etudier la structure et la connectivite des populations de sabres noirs (Aphanopus carbo), une espece demersale migratrice, echantillonnees le long d'un gradient couvrant une bonne partie de l'aire de repartition connue de l'espece dans le nord-est de l'Atlantique. Pour chaque etape du cycle de vie echantillonnee, les poissons captures dans des lieux differents presentent des concentrations semblables d'elements en traces et d'isotopes stables dans les otolites, alors que la composition des otolites varie grandement d'une etape du cycle de vie a l'autre. Les concentrations d'isotopes d'oxygene indiquent l'existence de migrations ontogeniques a partir de lieux caracterises par des eaux relativement chaudes durant la croissance des larves, vers des eaux plus froides a mesure que les poissons vieillissent. L'analyse de microsatellites d'ADN semble egalement indiquer une absence de structure genetique entre les differents lieux echantillonnes. L'approche multidisciplinaire employee donne collectivement a penser que les individus d'A. carbo effectuent une migration ontogenetique d'echelle oceanique qui commence par le frai dans des regions meridionales d'eau chaude de la Macaronesie (potentiellement dominees par la region de Madere), suivi du deplacement d'une grande partie des poissons immatures vers les pentes continentales de regions septentrionales, oU ils s'alimentent. Nos resultats constituent les premieres donnees concluantes permettant de circonscrire le circuit emprunte par cette espece au cours de son cycle de vie et d'entrevoir la structure du stock a l'echelle de l'Atlantique Nord. [Traduit par la Redaction], Introduction For most deep-sea fish, there is rather limited information on general ecology, life cycles, and population structure (Begg et al. 1999). In particular, the extent of large-scale migrations in [...]

The pencil cardinal Epigonus denticulatus is a small deep‐water fish inhabiting continental slopes usually between 300 and 600 m depth. We report the first record of E. denticulatus in the Azores archipelago, where one specimen was found floating by fisherman off Faial island. Meristic and morphometric characters are in accordance with those reported for the species and molecular analyses further supported species identity. The record of E. denticulatus as a native species in the Azores increases the number of Epigonus species in the region to a total of three. [ABSTRACT FROM AUTHOR]

The microbiome plays a key role in the health of all metazoans. Whether and how the microbiome favors the ad-aptation processes of organisms to extreme conditions, such as those of Antarctica, which are incompatible with most metazoans, is still unknown. We investigated the microbiome of three endemic and widespread species of Antarctic polychaetes: Leitoscoloplos geminus, Aphelochaeta palmeri, and Aglaophamus trissophyllus. We report here that these invertebrates contain a stable bacterial core dominated by Meiothermus and Anoxybacillus, equipped with a versatile genetic makeup and a unique portfolio of proteins useful for coping with extremely cold conditions as revealed by pangenomic and metaproteomic analyses. The close phylosymbiosis between Meiothermus and Anoxybacillus and these Antarctic polychaetes indicates a connection with their hosts that started in the past to support holobiont adaptation to the Antarctic Ocean. The wide suite of bacterial cryoprotective proteins found in Antarctic polychaetes may be useful for the development of nature-based biotechnological applications. [ABSTRACT FROM AUTHOR]

The presence of the opal chimaera, Chimaera opalescens, is reported for the first time in the deep waters of the Azores, with the capture of four specimens by fishermen and the video recording of an additional five individuals. Species identification was supported by the 646 bp sequenced fragment of the mitochondrial gene cytochrome oxidase subunit I. Because C. opalescens is a recently recognised species that had been recurrently misidentified as rabbitfish, Chimaera monstrosa, the historical data of C. monstrosa in the Azores were reviewed to assess the possible presence of both Chimaera species in the region. Although several authors have reported the occurrence of C. monstrosa in the Azorean waters since the 1800s, the majority of these are based on only three specimens caught during the late 1800s. The investigation performed using literature and examination of the museum specimens still available concluded that the most likely scenario is that C. monstrosa is absent from the Azores and past records of that species in the region are most likely misidentifications of C. opalescens., (© 2020 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of The Fisheries Society of the British Isles.)