Candidatus (Ca.) Allocryptoplasma is a newly identified, genetically diverse genus of vector-borne bacteria closely related to established blood-borne zoonotic pathogens, including Anaplasma, Ehrlichia, and Neoehrlichia species. Ca. Allocryptoplasma is a globally distributed pathogen detected across taxonomically diverse tick species and varied ecological niches. It maintains a complex enzootic circulation involving multiple vertebrate classes, including birds, small mammals, primates, and particularly reptiles, which serve as reservoir hosts. Methods: To characterize this emerging agent, multi-locus genetic DNA sequence analyses using the maximum likelihood method were performed on 16S rRNA, sucA, and rpoB genes amplified from the blood and vectors of marine iguanas and lizard species sampled across multiple islands in the Galápagos archipelago. Results: The compiled genomic data demonstrate that the Ca. Allocryptoplasma detected in the Galápagos lizards and marine iguanas represents a distinct lineage and a novel Ca. Allocryptoplasma species. Conclusions: Given its broad host plasticity, widespread geographic footprint, and vector-mediated transmission, the potential of Ca. Allocryptoplasma as a hidden, emerging zoonotic blood pathogen warrants intensive further evaluation.

Although the ability to sense Earth's magnetic field is phylogenetically widespread, receptors for the magnetic sense have not been identified unequivocally in any animal. Because magnetic fields penetrate biological tissue, magnetoreceptors could hypothetically exist anywhere in the body. To investigate the location of magnetoreceptors in juvenile loggerhead sea turtles (Caretta caretta), we attached a weak magnet, which generated a magnetic disturbance over a small localized area, to three anatomical regions (head, mid-body and posterior). We then observed responses of turtles to magnetic map cues they had been conditioned to associate with food. Responses to the food-associated field decreased significantly when a magnet was attached to the head, but no such disruption occurred when the magnet was placed at the other locations. The results provide the first evidence for cephalic magnetoreceptors in turtles and provide a simple methodology that can be used to help localize receptors in other magnetoreceptive animals.

Although some migratory animals can derive directional (compass) and positional (map) information from Earth's magnetic field, the underlying mechanisms of magnetic sensing have remained enigmatic. One hypothesis proposes that crystals of the mineral magnetite (Fe3O4) function in magnetoreception, a concept bolstered by findings that brief, strong magnetic pulses capable of reversing the magnetic dipole moment of magnetite affect magnetic orientation responses of several animals. Disentangling whether such pulses affected an animal's magnetic compass sense or magnetic map sense, however, has often been difficult. Here, we investigated the effect of a magnetic pulse on the magnetic map sense of loggerhead sea turtles (Caretta caretta) using an established conditioning assay that requires turtles to use magnetic map information but not their magnetic compass. We report that a magnetic pulse disrupted turtle responses, consistent with the interpretation that the magnetic map sense of turtles is based at least partly on magnetite-based magnetoreceptors.

While accurate engineered solutions to determine global position require vast networks of well-maintained transponder stations, many animals can solve this problem using only Earth’s magnetic field. Moreover, animals are capable of this feat despite evidence suggesting that the magnetic sense operates at an extremely low signal-to-noise ratio. As such, this sense may provide valuable insights for the engineer. Here, we explore neuromorphic encoding strategies that may underlie this ability in animals and test their ability to accurately encode noisy magnetic information. We describe sparse encoding strategies that may function in this sense, with systems composed of as few as eight receptors and tens of neurons. We also find that neural architecture based on the arthropod central complex (implicated in other orientation tasks) is particularly robust to encoding noisy magnetic field information.

The Galápagos marine iguana (Amblyrhynchus cristatus), the world's only marine lizard, feeds predominantly on algae. Owing to warming waters and reduced upwelling, algal abundance is reduced during El Niño events, causing high iguana mortality. During such periods, adult iguanas may shrink in size, a compelling phenomenon that has been suggested as an adaptation to reduce energetic needs. However, shifts in energy consumption have never been tested directly. We measured the body condition and metabolic rates of marine iguanas during an El Niño year and the subsequent neutral year. During El Niño, body mass relative to length was 17% lower, girth relative to length was 12% lower, and resting metabolic rates were 20% lower. This supports the hypothesis that marine iguanas partly offset the adverse effect of El Niño by an active response aimed at reducing their energy consumption, complementary to the energy-saving effect of body size reduction. Future ocean warming could force this endemic species to resort to such strategies increasingly often, and will likely exacerbate the already-high mortality rates caused by these events.

Australian migratory moths use the night sky to maintain their course when they travel long distances to shelter in cool caves during the arid summer. Australian migratory moths use the night sky to maintain their course when they travel long distances to shelter in cool caves during the arid summer.

Growing evidence indicates that migratory animals exploit the magnetic field of the Earth for navigation, both as a compass to determine direction and as a map to determine geographical position1. It has long been proposed that, to navigate using a magnetic map, animals must learn the magnetic coordinates of the destination2,3, yet the pivotal hypothesis that animals can learn magnetic signatures of geographical areas has, to our knowledge, yet to be tested. Here we report that an iconic navigating species, the loggerhead turtle (Caretta caretta), can learn such information. When fed repeatedly in magnetic fields replicating those that exist in particular oceanic locations, juvenile turtles learned to distinguish magnetic fields in which they encountered food from magnetic fields that exist elsewhere, an ability that might underlie foraging site fidelity. Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception4-6, suggesting that the magnetic map sense of the turtle does not rely on this mechanism. By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles.

Marine iguanas occasionally face severe food shortages because of algal dieback during El Ni & ntilde;o events. Research on their adaptations to these periods has highlighted their unique ability to shrink in body length, which reduces their energetic needs. Additional mechanisms, like sustaining lower body temperatures and metabolic rates, could potentially also lower energy consumption, but have never been examined. We measured 665 iguanas over an 11-year period including three El Ni & ntilde;o events, and examined how heart rates (a proxy for metabolic rates) and body temperatures change with sea-surface temperature oscillations (Oceanic Ni & ntilde;o Index, ONI). Heart rate (adjusting for body size, temperature, season, and study site) was negatively correlated with ONI and lower during El Ni & ntilde;o, whereas the adjusted body temperature did not correlate with ONI or differ between El Ni & ntilde;o and other periods. We therefore hypothesize that marine iguanas can depress their metabolic rates in response to the harsh conditions, an adaptation that is complementary to shrinking and may further enhance their survival through periods of limited food. Direct metabolic measurements are needed to test this hypothesis.

Semiterrestrial crabs have evolved to adjust to the challenges of living on land. Burrowing animals, including crabs, experience a unique mechanical environment featuring compressive stress from the elastic rebound of burrow walls, the weight of overlying sediments, shear forces from the flow of fluid pumped into burrows by the animals for oxygen, and forces from fluid flow through the surrounding porous sediment. Mechanosensory systems in burrowing animals likely play a key role in predator-prey ecology, with crabs potentially sensing propagating pressure waves generated by other animals (e.g., bird predators walking on overlying soil).

Achieving long-term retention of pop-up satellite archival tags (PSATs) has proven difficult for all fishes but is particularly challenging for small migrant species due to the relatively large size of tags. In this study, the authors tested the latest and smallest PSAT model on the market, the mark-report satellite tag (mrPAT), and developed a simple, cost-effective method of tag attachment on sheepshead Archosargus probatocephalus (Walbaum 1792), a small marine fish. During laboratory trials, the method of tag attachment used in this study outperformed the existing methods with two c. 40 cm fish retaining their tags for 3 months (the duration of the laboratory study). During field deployments, data were successfully obtained for 17 of the 25 tagged fish [37-50 cm fork length (FL)]. Of these, 14 tags (82%) remained on the fish until the pre-programmed release date resulting in tag retention times of up to 172 days (mean: 140 days). The investigation represents the first extensive study into the feasibility of PSATs for monitoring fishes in this size range. The authors demonstrate that their method of attachment and this latest PSAT model are feasible for c. 5-month deployments on fishes that are relatively small (c. 45 cm FL). These results with A. probatocephalus represent a potentially significant advance in PSAT methodology for fishes of this size. Future investigations are needed to determine if this method is transferrable to other species in the same size range.

Intraocular pressure using rebound tonometry in the Galápagos marine iguana (Amblyrhynchus cristatus)

In June of 2013, our team embarked on the first of what would be many projects investigating the health of Galápagos wildlife. With a permit from the Galápagos National Park (PNG) in progress, and the support of the Galápagos Science Center (GSC), three of us (Greg Lewbart, Max Hirschfeld, Ken Lohmann), along with PNG Ranger Juan Garcia and several GSC volunteers, initiated and completed a 2-day health assessment of 28 green turtles (Chelonia mydas) and a single hawksbill turtle (Eretmochelys imbricata). While waiting for our research permit and our aviso de campo (field permit) to be finalized, we had almost a week to explore San Cristóbal and think about future projects related to veterinary medicine and wild animal welfare. A literature search turned up hundreds of articles on wildlife evolution, natural history, ecology, genetics, invasive species eradication, anatomy, and physiology. The veterinary literature was limited to about five dozen publications, most focused on avian species. Many avian taxa were covered and included topics such as parasites, bacterial diseases, viral diseases, pollution, and baseline health assessments (Calle et al. 2017). Very few papers addressed health and diseases of reptiles, and we decided this would be a good area to focus.

In addition to providing animals with a source of directional or ‘compass’ information, Earth’s magnetic field also provides a potential source of positional or ‘map’ information that animals might exploit to assess location. In less than a generation, the idea that animals use Earth’s magnetic field as a kind of map has gone from a contentious hypothesis to a well-established tenet of animal navigation. Diverse animals ranging from lobsters to birds are now known to use magnetic positional information for a variety of purposes, including staying on track along migratory pathways, adjusting food intake at appropriate points in a migration, remaining within a suitable oceanic region, and navigating toward specific goals. Recent findings also indicate that sea turtles, salmon, and at least some birds imprint on the magnetic field of their natal area when young and use this information to facilitate return as adults, a process that may underlie long-distance natal homing (a.k.a. natal philopatry) in many species. Despite recent progress, much remains to be learned about the organization of magnetic maps, how they develop, and how animals use them in navigation.

Radio frequency electromagnetic noise (RF) of anthropogenic origin has been shown to disrupt magnetic orientation behavior in some animals. Two sources of natural RF might also have the potential to disturb magnetic orientation behavior under some conditions: solar RF and atmospheric RF. In this review, we outline the frequency ranges and electric/magnetic field magnitudes of RF that have been shown to disturb magnetoreceptive behavior in laboratory studies and compare these to the ranges of solar and atmospheric RF. Frequencies shown to be disruptive in laboratory studies range from 0.1 to 10 MHz, with magnetic magnitudes as low as 1 nT reported to have effects. Based on these values, it appears unlikely that solar RF alone routinely disrupts magnetic orientation. In contrast, atmospheric RF does sometimes exceed the levels known to disrupt magnetic orientation in laboratory studies. We provide a reference for when and where atmospheric RF can be expected to reach these levels, as well as a guide for quantifying RF measurements.

As the largest and most diverse vertebrate group on the planet, fishes have evolved an impressive array of sensory abilities to overcome the challenges associated with navigating the aquatic realm. Among these, the ability to detect Earth's magnetic field, or magnetoreception, is phylogenetically widespread and used by fish to guide movements over a wide range of spatial scales ranging from local movements to transoceanic migrations. A proliferation of recent studies, particularly in salmonids, has revealed that fish can exploit Earth's magnetic field not only as a source of directional information for maintaining consistent headings, but also as a kind of map for determining location at sea and for returning to natal areas. Despite significant advances, much about magnetoreception in fishes remains enigmatic. How fish detect magnetic fields remains unknown and our understanding of the evolutionary origins of vertebrate magnetoreception would benefit greatly from studies that include a wider array of fish taxa. The rich diversity of life-history characteristics that fishes exhibit, the wide variety of environments they inhabit, and their suitability for manipulative studies, make fishes promising subjects for magnetoreception studies.

Magnetotactic bacteria (MTB) are a diverse group of highly motile Gram-negative microorganisms with the common ability to orient along magnetic field lines, a behavior known as magnetotaxis. Ubiquitous in aquatic sediment environments, MTB are often microaerophilic and abundant at the oxic/anoxic interface. Magnetic field sensing is accomplished using intracellular, membrane-encased, iron-containing minerals known as magnetosomes. The chemistry, morphology and arrangement of magnetosomes differs substantially among different MTB. Although magnetic field sensing mechanisms, genetic bases and protein functions have been elucidated in select model organisms such as the Magnetospirillum strains and Desulfovibrio RS-1, not all findings are applicable to diverse clades of MTB. As the number of identified species has increased, it has become evident that many of the characteristics and mechanisms once presumed to be prototypical of MTB are in fact not universal. Here we present a general overview of the current state of MTB research for readers outside of the realm of prokaryotic research, focusing on recent discoveries, knowledge gaps and future directions. In addition, we report new insights acquired using holographic technology to observe and quantify microbial responses in magnetic fields that are earth-strength or weaker, providing a new ecophysiological approach to in situ MTB research.