Computational analysis of vertebrate myoglobins reveals aggregation resistance in aquatic birds and higher surface hydrophobicity in fish

Myoglobin is the major oxygen carrying protein in vertebrate muscle. Previous studies identified in secondarily aquatic mammalian lineages high myoglobin net charge, which serves to prevent aggregation at the extremely high intracellular myoglobin concentrations found in these species. However, it is unknown how aquatic birds that dive for extended durations prevent myoglobin aggregation at their high intracellular myoglobin concentrations. It is also unknown whether secondarily aquatic lineages reduced the surface hydrophobicity of their myoglobins to prevent aggregation. Here, we used a deep learning-predicted distance-based protein folding algorithm to model the tertiary structures of 302 vertebrate myoglobin orthologs and performed a comparative analysis of their predicted net charge and surface hydrophobicities. The results suggest that aquatic avian divers, such as penguins and diving ducks, evolved highly charged myoglobins to reduce aggregation propensity and allow greater storage of oxygen for extended underwater foraging. High myoglobin net charge was also identified in golden eagles, a species that routinely suffers high-altitude hypoxia. Although no general association was found between myoglobin surface hydrophobicity and intracellular concentration, comparison of predicted net charge and surface hydrophobicities revealed significant differences between major vertebrate classes; bird myoglobins are the most positively charge, reptile myoglobins are the most negatively charged, and the myoglobins of ray-finned fish (Actinopterygii) have higher surface hydrophobicity than those of lobe-finned fish (Sarcopterygii). Our findings indicate the convergent evolution of high myoglobin net charge in aquatic birds and mammals, and offer novel insights into the diversification of myoglobin among vertebrate clades.

The pathogenesis of a North American H5N2 clade 2.3.4.4 group A highly pathogenic avian influenza virus in surf scoters (Melanitta perspicillata)

Background Aquatic waterfowl, particularly those in the order Anseriformes and Charadriiformes, are the ecological reservoir of avian influenza viruses (AIVs). Dabbling ducks play a recognized role in the maintenance and transmission of AIVs. Furthermore, the pathogenesis of highly pathogenic AIV (HPAIV) in dabbling ducks is well characterized. In contrast, the role of diving ducks in HPAIV maintenance and transmission remains unclear. In this study, the pathogenesis of a North American A/Goose/1/Guangdong/96-lineage clade 2.3.4.4 group A H5N2 HPAIV, A/Northern pintail/Washington/40964/2014, in diving sea ducks (surf scoters, Melanitta perspicillata) was characterized. Results Intrachoanal inoculation of surf scoters with A/Northern pintail/Washington/40964/2014 (H5N2) HPAIV induced mild transient clinical disease whilst concomitantly shedding high virus titers for up to 10 days post-inoculation (dpi), particularly from the oropharyngeal route. Virus shedding, albeit at low levels, continued to be detected up to 14 dpi. Two aged ducks that succumbed to HPAIV infection had pathological evidence for co-infection with duck enteritis virus, which was confirmed by molecular approaches. Abundant HPAIV antigen was observed in visceral and central nervous system organs and was associated with histopathological lesions. Conclusions Collectively, surf scoters, are susceptible to HPAIV infection and excrete high titers of HPAIV from the respiratory and cloacal tracts whilst being asymptomatic. The susceptibility of diving sea ducks to H5 HPAIV highlights the need for additional research and surveillance to further understand the contribution of diving ducks to HPAIV ecology.

Nonbreeding Duck Use at Central Flyway National Wildlife Refuges

Within the U.S. portion of the Central Flyway, the U.S. Fish and Wildlife Service manages waterfowl on numerous individual units (i.e., Refuges) within the National Wildlife Refuge System. Presently, the extent of waterfowl use that Refuges receive and the contribution of Refuges to waterfowl populations (i.e., the proportion of the Central Flyway population registered at each Refuge) remain unassessed. Such an evaluation would help determine to what extent Refuges support waterfowl relative to stated targets, aid in identifying species requiring management attention, inform management targets, and improve fiscal efficiencies. Using historic monitoring data (1954–2008), we performed this assessment for 23 Refuges in Texas, New Mexico, Oklahoma, Kansas, and Nebraska during migration and wintering months (October–March). We examined six dabbling ducks and two diving ducks, plus all dabbling ducks and all diving ducks across two periods (long-term [all data] and short-term [last 10 October–March periods]). Individual Refuge use was represented by the sum of monthly duck count averages for October–March. We used two indices of Refuge contribution: peak contribution and January contribution. Peak contribution was the highest monthly count average for each October–March period divided by the indexed population total for the Central Flyway in the corresponding year; January contribution used the January count average divided by the corresponding population index. Generally, Refuges in Kansas, Nebraska, and New Mexico recorded most use and contribution for mallards Anas platyrhynchos. Refuges along the Texas Gulf Coast recorded most use and contribution for other dabbling ducks, with Laguna Atascosa and Aransas (including Matagorda Island) recording most use for diving ducks. The long-term total January contribution of the assessed Refuges to ducks wintering in the Central Flyway was greatest for green-winged teal Anas crecca with 35%; 12–15% for American wigeon Mareca americana, gadwall Mareca strepera, and northern pintail Anas acuta; and 7–8% for mallard and mottled duck Anas fulvigula. Results indicated that the reliance on the National Wildlife Refuge System decreased for these ducks, with evidence suggesting that, for several species, the assessed Refuges may be operating at carrying capacity. Future analyses could be more detailed and informative were Refuges to implement a single consistent survey methodology that incorporated estimations of detection bias in the survey process, while concomitantly recording habitat metrics on and neighboring each Refuge.

The cranial morphometrics of the wildfowl (Anatidae)

Wildfowl (Anatidae) are a diverse group of birds and globally distributed. These birds feed by widely varying methods, there are generalist and specialist species. In a number of vertebrate taxa trophic specializations have led to distinct differences in the morphology of the skull, like in birds. Our knowledge and understanding of the relationship between cranial morphology and feeding mechanism of wildfowl are limited. The aim of this article is to increase our knowledge of the relationship between skull shape and foraging habits and find the identifiable attributes of the differently adapted groups. We used morphometric methods with 7 linear measurements of the skull. We used principal component (PC) analysis to identify the groups with different foraging habits. The PCs were related to measurements which represent the demanded muscle mass for feeding and the amount of capable food items. The grazers have a narrower bill and bigger bone surface which requires more muscle tissue than the broad billed filter-feeders. We observed the structural and functional differences between grazers and filter-feeders. There are no important differences in the bill measurements between omnivore dabbling and diving ducks. Only the bill is not enough to deduce the foraging habits.

Low-Pathogenic Influenza A Viruses in North American Diving Ducks Contribute to the Emergence of a Novel Highly Pathogenic Influenza A(H7N8) Virus

ABSTRACT Introductions of low-pathogenic avian influenza (LPAI) viruses of subtypes H5 and H7 into poultry from wild birds have the potential to mutate to highly pathogenic avian influenza (HPAI) viruses, but such viruses' origins are often unclear. In January 2016, a novel H7N8 HPAI virus caused an outbreak in turkeys in Indiana, USA. To determine the virus's origin, we sequenced the genomes of 441 wild-bird origin influenza A viruses (IAVs) from North America and subjected them to evolutionary analyses. The results showed that the H7N8 LPAI virus most likely circulated among diving ducks in the Mississippi flyway during autumn 2015 and was subsequently introduced to Indiana turkeys, in which it evolved high pathogenicity. Preceding the outbreak, an isolate with six gene segments (PB2, PB1, PA, HA, NA, and NS) sharing >99% sequence identity with those of H7N8 turkey isolates was recovered from a diving duck sampled in Kentucky, USA. H4N8 IAVs from other diving ducks possessed five H7N8-like gene segments (PB2, PB1, NA, MP, and NS; >98% sequence identity). Our findings suggest that viral gene constellations circulating among diving ducks can contribute to the emergence of IAVs that affect poultry. Therefore, diving ducks may serve an important and understudied role in the maintenance, diversification, and transmission of IAVs in the wild-bird reservoir. IMPORTANCE In January 2016, a novel H7N8 HPAI virus caused a disease outbreak in turkeys in Indiana, USA. To determine the origin of this virus, we sequenced and analyzed 441 wild-bird origin influenza virus strains isolated from wild birds inhabiting North America. We found that the H7N8 LPAI virus most likely circulated among diving ducks in the Mississippi flyway during autumn 2015 and was subsequently introduced to Indiana turkeys, in which it evolved high pathogenicity. Our results suggest that viral gene constellations circulating among diving ducks can contribute to the emergence of IAVs that affect poultry. Therefore, diving ducks may play an important and understudied role in the maintenance, diversification, and transmission of IAVs in the wild-bird reservoir. Our study also highlights the importance of a coordinated, systematic, and collaborative surveillance for IAVs in both poultry and wild-bird populations.