Hunting bats adjust their echolocation to receive weak prey echoes for clutter reduction

This study was funded by the Carlsberg Semper Ardens grant to P.T.M. and by the Emmy Noether program of the Deutsche Forschungsgemeinschaft (DFG; German Research Foundation, grant no. 241711556) to H.R.G. All experiments were carried out under the following licenses: 721/12.06.2017, 180/07.08.2018, and 795/17.05.2019.How animals extract information from their surroundings to guide motor patterns is central to their survival. Here, we use echo-recording tags to show how wild hunting bats adjust their sensory strategies to their prey and natural environment. When searching, bats maximize the chances of detecting small prey by using large sensory volumes. During prey pursuit, they trade spatial for temporal information by reducing sensory volumes while increasing update rate and redundancy of their sensory scenes. These adjustments lead to very weak prey echoes that bats protect from interference by segregating prey sensory streams from the background using a combination of fast-acting sensory and motor strategies. Counterintuitively, these weak sensory scenes allow bats to be efficient hunters close to background clutter broadening the niches available to hunt for insects.Publisher PDFPeer reviewe

A Computational Systems Biology Software Platform for Multiscale Modeling and Simulation: Integrating Whole-Body Physiology, Disease Biology, and Molecular Reaction Networks

Today, in silico studies and trial simulations already complement experimental approaches in pharmaceutical R&D and have become indispensable tools for decision making and communication with regulatory agencies. While biology is multiscale by nature, project work, and software tools usually focus on isolated aspects of drug action, such as pharmacokinetics at the organism scale or pharmacodynamic interaction on the molecular level. We present a modeling and simulation software platform consisting of PK-Sim® and MoBi® capable of building and simulating models that integrate across biological scales. A prototypical multiscale model for the progression of a pancreatic tumor and its response to pharmacotherapy is constructed and virtual patients are treated with a prodrug activated by hepatic metabolization. Tumor growth is driven by signal transduction leading to cell cycle transition and proliferation. Free tumor concentrations of the active metabolite inhibit Raf kinase in the signaling cascade and thereby cell cycle progression. In a virtual clinical study, the individual therapeutic outcome of the chemotherapeutic intervention is simulated for a large population with heterogeneous genomic background. Thereby, the platform allows efficient model building and integration of biological knowledge and prior data from all biological scales. Experimental in vitro model systems can be linked with observations in animal experiments and clinical trials. The interplay between patients, diseases, and drugs and topics with high clinical relevance such as the role of pharmacogenomics, drug–drug, or drug–metabolite interactions can be addressed using this mechanistic, insight driven multiscale modeling approach

Top-Down Control of Herbivory by Birds and Bats in the Canopy of Temperate Broad-Leaved Oaks (Quercus robur)

The intensive foraging of insectivorous birds and bats is well known to reduce the density of arboreal herbivorous arthropods but quantification of collateral leaf damage remains limited for temperate forest canopies

The lugworm Abarenicola affinis (Arenicolidae, Polychaeta) in tidal flats of Otago, southern New Zealand.

Lugworms (Polychaeta: Arenicolidae) occur in coastal sediments worldwide and can dominate the macrofauna of intertidal sand and mud flats. They have been recognised as ecosystem engineers due to their bioturbating and bioirrigating activities, which can profoundly influence sediment properties and other biota. In view of the potentially significant role of lugworms, the present study examined aspects of the biology and ecology of the endemic lugworm Abarenicola affinis in coastal environments of southern New Zealand. Abarenicola affinis occur in tidal inlets along the Otago coast with a patchy distribution. Mean abundance ranged between 4 and 21 individuals per m² across four different tidal flats (Papanui, Hoopers, Purakaunui inlets, and Harwood in Otago Harbour), resulting in an overall mean abundance of 11 individuals per m². Two investigated lugworm populations in neighbouring inlets were stable across seasons, but exhibited differences in terms of their spatial distribution, biomass, body size, and burrow depth. Lugworm populations appeared to be limited by intertidal seagrass (Zostera muelleri), which had a significant negative influence on Abarenicola affinis abundance and biomass in one inlet. In laboratory experiments, seagrass root‐rhizome matrices imposed restrictions on the burrowing ability of Abarenicola affinis but did not prevent lugworms from burrowing and feeding similar to those in unvegetated sediment. Lugworms in seagrass treatments, particularly small individuals which stayed within the root‐rhizome matrix, processed less sediment than those in unvegetated treatments, suggesting that they may have exploited seagrass detritus as an additional food source. Sediment turnover by Abarenicola affinis was found to be stable over seasons, with lugworms being mostly active when burrows were submerged during high tide. Defaecation frequencies were shorter for small lugworms than for large ones, whereas the faecal amounts increased with increasing lugworm size. An annual sediment turnover estimate for an intertidal Abarenicola affinis population was calculated at 24.4 kg sediment dry weight per m², equivalent to a sediment depth of 2 cm. Habitat modification by lugworms had little influence on the macrofaunal assemblage composition in one tidal flat, and abiotic factors such as tidal level and proportion of sediment fines best explained assemblage patterns. Manipulative small‐scale exclusion of lugworms from otherwise densely populated areas did not result in significant changes in macrofaunal assemblages, but showed a subtle promotional effect of Abarenicola affinis on abundance of macrofauna, in particular dominant amphipods, at one of two sampling occasions. The effect was inferior to the high spatial variation in macrofaunal assemblages at the other sampling occasion. The study indicates that the impact of Abarenicola affinis on sediment and associated biota is spatially dependent and may be generally weak. As the distribution of this species is influenced by abiotic and biotic habitat variables, those factors will have, in turn, a profound influence on its engineering capacity. Abarenicola affinis does not reach the dominance and ecological importance as documented for lugworm species in other parts of the world (e.g. Arenicola marina in Europe), due to smaller and patchier populations, relatively smaller sediment turnover capacity, and less distinct influences on macrobenthic infauna. Future research is needed to gain more information on the species’ population dynamics, and to elucidate ways in which these lugworms interact with their abiotic and biotic environment in coastal ecosystems of New Zealand

The lugworm Abarenicola affinis (Arenicolidae, Polychaeta) in tidal flats of Otago, southern New Zealand.

Lugworms (Polychaeta: Arenicolidae) occur in coastal sediments worldwide and can dominate the macrofauna of intertidal sand and mud flats. They have been recognised as ecosystem engineers due to their bioturbating and bioirrigating activities, which can profoundly influence sediment properties and other biota. In view of the potentially significant role of lugworms, the present study examined aspects of the biology and ecology of the endemic lugworm Abarenicola affinis in coastal environments of southern New Zealand. Abarenicola affinis occur in tidal inlets along the Otago coast with a patchy distribution. Mean abundance ranged between 4 and 21 individuals per m² across four different tidal flats (Papanui, Hoopers, Purakaunui inlets, and Harwood in Otago Harbour), resulting in an overall mean abundance of 11 individuals per m². Two investigated lugworm populations in neighbouring inlets were stable across seasons, but exhibited differences in terms of their spatial distribution, biomass, body size, and burrow depth. Lugworm populations appeared to be limited by intertidal seagrass (Zostera muelleri), which had a significant negative influence on Abarenicola affinis abundance and biomass in one inlet. In laboratory experiments, seagrass root‐rhizome matrices imposed restrictions on the burrowing ability of Abarenicola affinis but did not prevent lugworms from burrowing and feeding similar to those in unvegetated sediment. Lugworms in seagrass treatments, particularly small individuals which stayed within the root‐rhizome matrix, processed less sediment than those in unvegetated treatments, suggesting that they may have exploited seagrass detritus as an additional food source. Sediment turnover by Abarenicola affinis was found to be stable over seasons, with lugworms being mostly active when burrows were submerged during high tide. Defaecation frequencies were shorter for small lugworms than for large ones, whereas the faecal amounts increased with increasing lugworm size. An annual sediment turnover estimate for an intertidal Abarenicola affinis population was calculated at 24.4 kg sediment dry weight per m², equivalent to a sediment depth of 2 cm. Habitat modification by lugworms had little influence on the macrofaunal assemblage composition in one tidal flat, and abiotic factors such as tidal level and proportion of sediment fines best explained assemblage patterns. Manipulative small‐scale exclusion of lugworms from otherwise densely populated areas did not result in significant changes in macrofaunal assemblages, but showed a subtle promotional effect of Abarenicola affinis on abundance of macrofauna, in particular dominant amphipods, at one of two sampling occasions. The effect was inferior to the high spatial variation in macrofaunal assemblages at the other sampling occasion. The study indicates that the impact of Abarenicola affinis on sediment and associated biota is spatially dependent and may be generally weak. As the distribution of this species is influenced by abiotic and biotic habitat variables, those factors will have, in turn, a profound influence on its engineering capacity. Abarenicola affinis does not reach the dominance and ecological importance as documented for lugworm species in other parts of the world (e.g. Arenicola marina in Europe), due to smaller and patchier populations, relatively smaller sediment turnover capacity, and less distinct influences on macrobenthic infauna. Future research is needed to gain more information on the species’ population dynamics, and to elucidate ways in which these lugworms interact with their abiotic and biotic environment in coastal ecosystems of New Zealand

Lugworm (Abarenicola affinis) in seagrass and unvegetated habitats

Abstract In Otago, southern New Zealand, the lugworm Abarenicola affinis resides in neighbouring tidal inlets with and without seagrass (Zostera muelleri). A comparison of abundance, body size and biomass of A. affinis between seagrass habitat (Papanui Inlet) and unvegetated habitat (Hoopers Inlet) showed little seasonal variation of these parameters in each habitat and relatively similar abundances between both habitats. In contrast, lugworm biomass was considerably lower in the seagrass habitat due to the lack of large individuals compared with unvegetated habitat. In the seagrass habitat, there was a significant negative influence of Z. muelleri below-ground biomass on abundance and biomass of A. affinis, indicating that seagrass affected lugworm burrowing and/or feeding processes. In contrast to the unvegetated habitat, where lugworms spread relatively evenly across the intertidal area, lugworms were mostly restricted to the upper intertidal zone in the seagrass habitat. The findings suggest that the extensive seagrass bed in the mid and low intertidal zones of Papanui Inlet limited lugworm distribution in an otherwise suitable habitat. Whereas small lugworms colonised seagrass areas, the largest individuals occurred only in unvegetated sediment and seemed to be more hampered by the presence of seagrass than smaller individuals. The findings highlight negative feedback between antagonistic ecosystem engineers, with the potential of seagrass physical structures (autogenic engineering) to impact negatively on lugworm activity (allogenic engineering)

The effect of cave illumination on bats

Artificial light at night has large impacts on nocturnal wildlife such as bats, yet its effect varies with wavelength of light, context, and across species involved. Here, we studied in two experiments how wild bats of cave-roosting species (Rhinolophus mehelyi, R. euryale, Myotis capaccinii and Miniopterus schreibersii) respond to LED lights of different colours. In dual choice experiments, we measured the acoustic activity of bats in response to neutral-white, red or amber LED at a cave entrance and in a flight room – mimicking a cave interior. In the flight room, M. capaccinii and M. schreibersii preferred red to white light, but showed no preference for red over amber, or amber over white light. In the cave entrance experiment, all light colours reduced the activity of all emerging species, yet red LED had the least negative effect. Rhinolophus species reacted most strongly, matching their refusal to fly at all under any light treatment in the flight room. We conclude that the placement and light colour of LED light should be considered carefully in lighting concepts for caves both in the interior and at the entrance. In a cave interior, red LED light could be chosen – if needed at all – for careful temporary illumination of areas, yet areas important for bats should be avoided based on the precautionary principle. At cave entrances, the high sensitivity of most bat species, particularly of Rhinolophus spp., towards light sources almost irrespective of colour, calls for utmost caution when illuminating cave entrances

Echolocating bats prefer a high risk-high gain foraging strategy to increase prey profitability

Predators that target multiple prey types are predicted to switch foraging modes according to prey profitability to increase energy returns in dynamic environments. Here, we use bat-borne tags and DNA metabarcoding of feces to test the hypothesis that greater mouse-eared bats make immediate foraging decisions based on prey profitability and changes in the environment. We show that these bats use two foraging strategies with similar average nightly captures of 25 small, aerial insects and 29 large, ground-dwelling insects per bat, but with much higher capture success in the air (76%) vs ground (30%). However, owing to the 3–20 times larger ground prey, 85% of the nightly food acquisition comes from ground prey despite the 2.5 times higher failure rates. We find that most bats use the same foraging strategy on a given night suggesting that bats adapt their hunting behavior to weather and ground conditions. We conclude that these bats use high risk-high gain gleaning of ground prey as a primary foraging tactic, but switch to aerial hunting when environmental changes reduce the profitability of ground prey, showing that prey switching matched to environmental dynamics plays a key role in covering the energy intake even in specialized predators

Green Fluorescent Protein-Tagged Adeno-Associated Virus Particles Allow the Study of Cytosolic and Nuclear Trafficking

To allow the direct visualization of viral trafficking, we genetically incorporated enhanced green fluorescent protein (GFP) into the adeno-associated virus (AAV) capsid by replacement of wild-type VP2 by GFP-VP2 fusion proteins. High-titer virus progeny was obtained and used to elucidate the process of nuclear entry. In the absence of adenovirus 5 (Ad5), nuclear translocation of AAV capsids was a slow and inefficient process: at 2 h and 4 h postinfection (p.i.), GFP-VP2-AAV particles were found in the perinuclear area and in nuclear invaginations but not within the nucleus. In Ad5-coinfected cells, isolated GFP-VP2-AAV particles were already detectable in the nucleus at 2 h p.i., suggesting that Ad5 enhanced the nuclear translocation of AAV capsids. The number of cells displaying viral capsids within the nucleus increased slightly over time, independently of helper virus levels, but the majority of the AAV capsids remained in the perinuclear area under all conditions analyzed. In contrast, independently of helper virus and with 10 times less virions per cell already observed at 2 h p.i., viral genomes were visible within the nucleus. Under these conditions and even with prolonged incubation times (up to 11 h p.i.), no intact viral capsids were detectable within the nucleus. In summary, the results show that GFP-tagged AAV particles can be used to study the cellular trafficking and nuclear entry of AAV. Moreover, our findings argue against an efficient nuclear entry mechanism of intact AAV capsids and favor the occurrence of viral uncoating before or during nuclear entry