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1. Habitat split as a driver of disease in amphibians

   https://doi.org/10.1111/brv.12927  

   Becker, C. Guilherme ; Greenspan, Sasha E. ; Martins, Renato A. ; Lyra, Mariana L. ; Prist, Paula ; Metzger, Jean Paul ; São Pedro, Vinicius ; Haddad, Célio F. B. ; Le Sage, Emily H. ; Woodhams, Douglas C. ; et al ( January 2023 , Biological Reviews)

   Anthropogenic habitat disturbance is fundamentally altering patterns of disease transmission and immunity across the vertebrate tree of life. Most studies linking anthropogenic habitat change and disease focus on habitat loss and fragmentation, but these processes often lead to a third process that is equally important:habitat split. Defined as spatial separation between the multiple classes of natural habitat that many vertebrate species require to complete their life cycles, habitat split has been linked to population declines in vertebrates, e.g. amphibians breeding in lowland aquatic habitats and overwintering in fragments of upland terrestrial vegetation. Here, we link habitat split to enhanced disease risk in amphibians (i) by reviewing the biotic and abiotic forces shaping elements of immunity and (ii) through a spatially oriented field study focused on tropical frogs. We propose a framework to investigate mechanisms by which habitat split influences disease risk in amphibians, focusing on three broad host factors linked to immunity: (i) composition of symbiotic microbial communities, (ii) immunogenetic variation, and (iii) stress hormone levels. Our review highlights the potential for habitat split to contribute to host‐associated microbiome dysbiosis, reductions in immunogenetic repertoire, and chronic stress, that often facilitate pathogenic infections and disease in amphibians and other classes of vertebrates. We highlight that targeted habitat‐restoration strategies aiming to connect multiple classes of natural habitats (e.g. terrestrial–freshwater, terrestrial–marine, marine–freshwater) could enhance priming of the vertebrate immune system through repeated low‐load exposure to enzootic pathogens and reduced stress‐induced immunosuppression.

    

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2. Aquatic Walking and Swimming Kinematics of Neonate and Juvenile Epaulette Sharks

   https://doi.org/10.1093/icb/icac127  

   Porter, Marianne E. ; Hernandez, Andrea V. ; Gervais, Connor R. ; Rummer, Jodie L. ( July 2022 , Integrative And Comparative Biology)

   The epaulette shark, Hemiscyllium ocellatum, is a small, reef-dwelling, benthic shark that—using its paired fins—can walk, both in and out of water. Within the reef flats, this species experiences short periods of elevated CO2 and hypoxia as well as fluctuating temperatures as reef flats become isolated with the outgoing tide. Past studies have shown that this species is robust (i.e., respiratory and metabolic performance, behavior) to climate change-relevant elevated CO2 levels as well as hypoxia and anoxia tolerant. However, epaulette shark embryos reared under ocean warming conditions hatch earlier and smaller, with altered patterns and coloration, and with higher metabolic costs than their current-day counterparts. Findings to date suggest that this species has adaptations to tolerate some, but perhaps not all, of the challenging conditions predicted for the 21st century. As such, the epaulette shark is emerging as a model system to understand vertebrate physiology in changing oceans. Yet, few studies have investigated the kinematics of walking and swimming, which may be vital to their biological fitness, considering their habitat and propensity for challenging environmental conditions. Given that neonates retain embryonic nutrition via an internalized yolk sac, resulting in a bulbous abdomen, while juveniles actively forage for worms, crustaceans, and small fishes, we hypothesized that difference in body shape over early ontogeny would affect locomotor performance. To test this, we examined neonate and juvenile locomotor kinematics during the three aquatic gaits they utilize—slow-to-medium walking, fast walking, and swimming—using 13 anatomical landmarks along the fins, girdles, and body midline. We found that differences in body shape did not alter kinematics between neonates and juveniles. Overall velocity, fin rotation, axial bending, and tail beat frequency and amplitude were consistent between early life stages. Data suggest that the locomotor kinematics are maintained between neonate and juvenile epaulette sharks, even as their feeding strategy changes. Studying epaulette shark locomotion allows us to understand this—and perhaps related—species’ ability to move within and away from challenging conditions in their habitats. Such locomotor traits may not only be key to survival, in general, as a small, benthic mesopredator (i.e., movements required to maneuver into small reef crevices to avoid aerial and aquatic predators), but also be related to their sustained physiological performance under challenging environmental conditions, including those associated with climate change—a topic worthy of future investigation.

    

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3. Divergent sensory and immune gene evolution in sea turtles with contrasting demographic and life histories

   https://doi.org/10.1073/pnas.2201076120  

   Bentley, Blair P. ; Carrasco-Valenzuela, Tomás ; Ramos, Elisa K. ; Pawar, Harvinder ; Souza Arantes, Larissa ; Alexander, Alana ; Banerjee, Shreya M. ; Masterson, Patrick ; Kuhlwilm, Martin ; Pippel, Martin ; et al ( February 2023 , Proceedings of the National Academy of Sciences)

   Sea turtles represent an ancient lineage of marine vertebrates that evolved from terrestrial ancestors over 100 Mya. The genomic basis of the unique physiological and ecological traits enabling these species to thrive in diverse marine habitats remains largely unknown. Additionally, many populations have drastically declined due to anthropogenic activities over the past two centuries, and their recovery is a high global conservation priority. We generated and analyzed high-quality reference genomes for the leatherback ( Dermochelys coriacea ) and green ( Chelonia mydas ) turtles, representing the two extant sea turtle families. These genomes are highly syntenic and homologous, but localized regions of noncollinearity were associated with higher copy numbers of immune, zinc-finger, and olfactory receptor (OR) genes in green turtles, with ORs related to waterborne odorants greatly expanded in green turtles. Our findings suggest that divergent evolution of these key gene families may underlie immunological and sensory adaptations assisting navigation, occupancy of neritic versus pelagic environments, and diet specialization. Reduced collinearity was especially prevalent in microchromosomes, with greater gene content, heterozygosity, and genetic distances between species, supporting their critical role in vertebrate evolutionary adaptation. Finally, diversity and demographic histories starkly contrasted between species, indicating that leatherback turtles have had a low yet stable effective population size, exhibit extremely low diversity compared with other reptiles, and harbor a higher genetic load compared with green turtles, reinforcing concern over their persistence under future climate scenarios. These genomes provide invaluable resources for advancing our understanding of evolution and conservation best practices in an imperiled vertebrate lineage. 

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4. Unchartered waters: Climate change likely to intensify infectious disease outbreaks causing mass mortality events in marine mammals

   https://doi.org/10.1111/gcb.15163  

   Sanderson, Claire E. ; Alexander, Kathleen A. ( June 2020 , Global Change Biology)

   Infectious disease emergence has increased significantly over the last 30 years, with mass mortality events (MMEs) associated with epizootics becoming increasingly common. Factors influencing these events have been widely studied in terrestrial systems, but remain relatively unexplored in marine mammals. Infectious disease‐induced MMEs (ID MMEs) have not been reported ubiquitously among marine mammal species, indicating that intrinsic (host) and/or extrinsic (environmental) ecological factors may influence this heterogeneity. We assess the occurrence of ID MMEs (1955–2018) across extant marine mammals (n = 129) in relation to key life‐history characteristics (sociality, trophic level, habitat breadth) and environmental variables (season, sea surface temperature [SST] anomalies, El Niño occurrence). Our results show that ID MMEs have been reported in 14% of marine mammal species (95% CI 9%–21%), with 72% (n = 36; 95% CI 56%–84%) of these events caused predominantly by viruses, primarily morbillivirus and influenza A. Bacterial pathogens caused 25% (95% CI 14%–41%) of MMEs, with only one being the result of a protozoan pathogen. Overall, virus‐induced MMEs involved a greater number of fatalities per event compared to other pathogens. No association was detected between the occurrence of ID MMEs and host characteristics, such as sociality or trophic level, but ID MMEs did occur more frequently in semiaquatic species (pinnipeds) compared to obligate ocean dwellers (cetaceans; χ² = 9.6,p = .002). In contrast, extrinsic factors significantly influenced ID MMEs, with seasonality linked to frequency (χ² = 19.85,p = .0002) and severity of these events, and global yearly SST anomalies positively correlated with their temporal occurrence (Z = 3.43,p = 2.7e‐04). No significant association was identified between El Niño and ID MME occurrence (Z = 0.28,p = .81). With climate change forecasted to increase SSTs and the frequency of extreme seasonal weather events, epizootics causing MMEs are likely to intensify with significant consequences for marine mammal survival.

    

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5. sFDvent: A global trait database for deep‐sea hydrothermal‐vent fauna

   https://doi.org/10.1111/geb.12975  

   Chapman, Abbie S. A. ; Beaulieu, Stace E. ; Colaço, Ana ; Gebruk, Andrey V. ; Hilario, Ana ; Kihara, Terue C. ; Ramirez‐Llodra, Eva ; Sarrazin, Jozée ; Tunnicliffe, Verena ; Amon, Diva J. ; et al ( July 2019 , Global Ecology and Biogeography)

   Traits are increasingly being used to quantify global biodiversity patterns, with trait databases growing in size and number, across diverse taxa. Despite growing interest in a trait‐based approach to the biodiversity of the deep sea, where the impacts of human activities (including seabed mining) accelerate, there is no single repository for species traits for deep‐sea chemosynthesis‐based ecosystems, including hydrothermal vents. Using an international, collaborative approach, we have compiled the first global‐scale trait database for deep‐sea hydrothermal‐vent fauna – sFDvent (sDiv‐funded trait database for theFunctionalDiversity ofvents). We formed a funded working group to select traits appropriate to: (a) capture the performance of vent species and their influence on ecosystem processes, and (b) compare trait‐based diversity in different ecosystems. Forty contributors, representing expertise across most known hydrothermal‐vent systems and taxa, scored species traits using online collaborative tools and shared workspaces. Here, we characterise the sFDvent database, describe our approach, and evaluate its scope. Finally, we compare the sFDvent database to similar databases from shallow‐marine and terrestrial ecosystems to highlight how the sFDvent database can inform cross‐ecosystem comparisons. We also make the sFDvent database publicly available online by assigning a persistent, unique DOI.

   Six hundred and forty‐six vent species names, associated location information (33 regions), and scores for 13 traits (in categories: community structure, generalist/specialist, geographic distribution, habitat use, life history, mobility, species associations, symbiont, and trophic structure). Contributor IDs, certainty scores, and references are also provided.

   Global coverage (grain size: ocean basin), spanning eight ocean basins, including vents on 12 mid‐ocean ridges and 6 back‐arc spreading centres.

   sFDvent includes information on deep‐sea vent species, and associated taxonomic updates, since they were first discovered in 1977. Time is not recorded. The database will be updated every 5 years.

   Deep‐sea hydrothermal‐vent fauna with species‐level identification present or in progress.

   .csv and MS Excel (.xlsx).

    

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