scholarly journals A kinematic analysis of Micrurus coral snakes reveals unexpected variation in stereotyped anti-predator displays within a mimicry system

2019 ◽  
Author(s):  
Talia Y. Moore ◽  
Shannon M. Danforth ◽  
Joanna G. Larson ◽  
Alison R. Davis Rabosky
Keyword(s):  
Stabilizing Selection ◽  
List Type ◽  
South American ◽  
Species Identity ◽  
Predator Prey ◽  
Curve Magnitude ◽  
Body Location ◽  
Critical Components ◽  
Common Signal ◽  
High Degree

AbstractWarning signals in chemically defended organisms are critical components of predator-prey interactions, often requiring multiple coordinated display components for a signal to be effective. When threatened by a predator, venomous coral snakes (genus Micrurus) display a vigorous, non-locomotory thrashing behaviour that has been only qualitatively described. Given the high-contrast and often colourful banding patterns of these snakes, this thrashing display is hypothesized to be a key component of a complex aposematic signal under strong stabilizing selection across species in a mimicry system.By experimentally testing snake response across simulated predator cues, we analysed variation in the presence and expression of a thrashing display across five species of South American coral snakes.Although the major features of the thrash display were conserved across species, we found significant variation in the propensity to perform a display at all, the duration of thrashing, and the curvature of snake bodies that was mediated by predator cue type, snake body size, and species identity. We also found an interaction between curve magnitude and body location that clearly shows which parts of the display vary most across individuals and species.Our results suggest that contrary to the assumption in the literature that all species and individuals perform the same display, a high degree of variation persists in thrashing behaviour exhibited by Micrurus coral snakes despite presumably strong selection to converge on a common signal. This quantitative behavioural characterization presents a new framework for analysing the non-locomotory motions displayed by snakes in a broader ecological context, especially for signalling systems with complex interaction across multiple modalities.

scholarly journals A Quantitative Analysis of Micrurus Coral Snakes Reveals Unexpected Variation in Stereotyped Anti-Predator Displays Within a Mimicry System

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
T Y Moore ◽  
S M Danforth ◽  
J G Larson ◽  
A R Davis Rabosky
Keyword(s):  
Stabilizing Selection ◽  
South American ◽  
Species Identity ◽  
Predator Prey ◽  
Signaling Systems ◽  
Curve Magnitude ◽  
Body Location ◽  
Critical Components ◽  
Common Signal ◽  
High Degree

Synopsis Warning signals in chemically defended organisms are critical components of predator–prey interactions, often requiring multiple coordinated display components for effective communication. When threatened by a predator, venomous coral snakes (genus Micrurus) display a vigorous, non-locomotory thrashing behavior that has previously been qualitatively described. Given the high contrast and colorful banding patterns of these snakes, this thrashing display is hypothesized to be a key component of a complex aposematic signal under strong stabilizing selection across species in a mimicry system. By experimentally testing snake response across simulated predator cues, we analyzed variation in the presence and expression of a thrashing display across five species of South American coral snakes. Although the major features of the thrash display were conserved across species, we found that predator cue type, snake body size, and species identity predict significant inter- and intraspecific variation in the propensity to perform a display, the duration of thrashing, and the curvature of snake bodies. We also found an interaction between curve magnitude and body location that clearly shows which parts of the display vary most across individuals and species. Our results suggest that contrary to the assumption that all Micrurus species and individuals perform the same display, a high degree of variation exists despite presumably strong selection to conserve a common signal. This quantitative behavioral characterization presents a new framework for analyzing the non-locomotory motions displayed by snakes in a broader ecological context, especially for signaling systems with complex interaction across multiple modalities.

scholarly journals Osteopontin and iCD8α cells promote intestinal intraepithelial lymphocyte homeostasis

2019 ◽  
Author(s):  
Ali Nazmi ◽  
Michael J. Greer ◽  
Kristen L. Hoek ◽  
M. Blanca Piazuelo ◽  
Joern-Hendrik Weitkamp ◽  
...  
Keyword(s):  
Immune Responses ◽  
Intestinal Inflammation ◽  
Intraepithelial Lymphocytes ◽  
Intestinal Lumen ◽  
Anatomical Location ◽  
List Type ◽  
Intestinal Intraepithelial Lymphocyte ◽  
Critical Components ◽  
Cellular Immune

AbstractIntestinal intraepithelial lymphocytes (IEL) comprise a diverse population of cells residing in the epithelium at the interface between the intestinal lumen and the sterile environment of the lamina propria. Because of this anatomical location, IEL are considered critical components of intestinal immune responses. Indeed, IEL are involved in many different immunological processes ranging from pathogen control to tissue stability. However, despite their critical importance in mucosal immune responses, very little is known about the homeostasis of different IEL subpopulations. The phosphoprotein osteopontin is important for critical physiological processes, including cellular immune responses such as survival of Th17 cells and homeostasis of NK cells, among others. Because of its impact in the immune system, we investigated the role of osteopontin in the homeostasis of IEL. Here, we report that mice deficient in the expression of osteopontin exhibit reduced numbers of the IEL subpopulations TCRγδ+, TCRβ+CD4+, TCRβ+CD4+CD8α+and TCRβ+CD8αα+cells in comparison to wild-type mice. For some IEL subpopulations the decrease in cells numbers could be attributed to apoptosis and reduced cell division. Moreover, we showin vitrothat exogenous osteopontin stimulates the survival of murine IEL subpopulations and unfractionated IEL derived from human intestines, an effect mediated by CD44, a known osteopontin receptor. We also show that iCD8α IEL, but not TCRγδ+IEL, TCRβ+IEL or intestinal epithelial cells, can promote survival of different IEL populations via osteopontin, indicating an important role for iCD8α cells in the homeostasis of IEL.Key PointsOsteopontin promotes homeostasis of mouse and human IEL, mediated by its ligand CD44iCD8α cells produce osteopontin which impacts the survival of other IELLack of osteopontin renders mice susceptible to intestinal inflammation

SOD polymorphism in the Xiphinema americanum-group (Nematoda: Longidoridae)

Nematology ◽  
2004 ◽  
Vol 6 (6) ◽  
pp. 867-876 ◽  
Author(s):  
Robert Robbins ◽  
Rui Lemos ◽  
Peter Nagy ◽  
Michael McKenry ◽  
Franco Lamberti ◽  
...  
Keyword(s):  
North American ◽  
South American ◽  
Homogeneous Groups ◽  
The Usa ◽  
Geographic Separation ◽  
High Degree ◽  
First Time ◽  
Large Groups ◽  
Single Enzyme ◽  
Group 1

AbstractIsoelectrofocusing of superoxide dismutase (SOD) isoforms was carried out on the extracts of 117 nematode populations belonging to the so-called Xiphinema americanum-group. These populations came from the USA (77), Chile (5), Argentina (1), Venezuela (5), Portugal (15), Italy (2), Crete (1), Montenegro (1), Slovakia (4), Hungary (3), Egypt (1) and India (2). A total of 17 bands of enzyme activity were observed in the screening, whilst single enzyme phenotypes showed from two to eight bands. The high degree of SOD polymorphism of this nematode collection was grouped by cluster analysis into seven distinct homogeneous groups characterised by specific combinations of SOD markers. Sub-groups could be discriminated for larger groups. The small Groups 3 and 5 were constituted mostly by populations from USA east coast states (i.e., NY and PA, respectively). The larger Group 1 resulted from the association of populations coming from various and distant North American States. In other large groups, North American populations were associated with South American and European populations. Overall, the data presented here suggest that geographic separation and different hosts do not seem to be the source of genetic diversity for the X. americanum-group. When an adequate number of populations were collected from the same country, the variability expressed by such a sub-sample was comparable to that of the whole nematode collection. For the first time, homogeneous populations of a large collection of X. americanum-group populations were associated by molecular means in order to explore further approaches that may help resolve the recalcitrant taxonomy and phylogeny of this much debated group.

scholarly journals Predator-induced flow disturbances alert prey, from the onset of an attack

2014 ◽  
Vol 281 (1790) ◽  
pp. 20141083 ◽  
Author(s):  
Jérôme Casas ◽  
Thomas Steinmann
Keyword(s):  
Prey Capture ◽  
Ground Effect ◽  
Just In Time ◽  
Soil Arthropods ◽  
Predator Prey ◽  
Flow Sensing ◽  
Predator Attack ◽  
Flow Disturbances ◽  
A Minor ◽  
High Degree

Many prey species, from soil arthropods to fish, perceive the approach of predators, allowing them to escape just in time. Thus, prey capture is as important to predators as prey finding. We extend an existing framework for understanding the conjoint trajectories of predator and prey after encounters, by estimating the ratio of predator attack and prey danger perception distances, and apply it to wolf spiders attacking wood crickets. Disturbances to air flow upstream from running spiders, which are sensed by crickets, were assessed by computational fluid dynamics with the finite-elements method for a much simplified spider model: body size, speed and ground effect were all required to obtain a faithful representation of the aerodynamic signature of the spider, with the legs making only a minor contribution. The relationship between attack speed and the maximal distance at which the cricket can perceive the danger is parabolic; it splits the space defined by these two variables into regions differing in their values for this ratio. For this biological interaction, the ratio is no greater than one, implying immediate perception of the danger, from the onset of attack. Particular attention should be paid to the ecomechanical aspects of interactions with such small ratio, because of the high degree of bidirectional coupling of the behaviour of the two protagonists. This conclusion applies to several other predator–prey systems with sensory ecologies based on flow sensing, in air and water.

Breeding

1935 ◽  
Vol 8 (4) ◽  
pp. 54-80
Keyword(s):  
Low Temperature ◽  
Moisture Content ◽  
Early Stage ◽  
Control Group ◽  
List Type ◽  
Type Number ◽  
Depressing Effect ◽  
Internal Organs ◽  
Completely Regular ◽  
High Degree

Growth of Chicken-Embryos. Das Wachstum des Hühnerembryos in Abhängigkeit von verschiedenen Temperaturen und Feuchtigkeitsgraden im Brutapparat. N. M. Schkljar. Archiv für Geflügelkunde, 1935, No. 5.Summary:1.A completely regular and strong growth of the hen embryos is obtained with a temperature of 38.4° C. (101.1° F.) and 64% moisture.2.A temperature of 39.9° C. (103.82° F.) and 62% moisture have a somewhat depressing effect on the developement of the embryos during the first six and last two days of the incubation, an increase in growth taking place on the 16th days.3.A high degree of moisture of 77% and a temperature of 38.3 ° C. (100.9° F.) prevent growth up to the 18th day, a decisive increase taking place after this date.4.With a low temperature of 37° C. (98.66° F.) and a moisture content of 63%, the developement of embryos remains noticeably backward, specially during the first few days. Under such conditions, as early as after the sixth day, growth in relation to the control group is delayed by two days.5.Between the increase in weigth and the developement of embryos, there exists, in an early stage, an inverted ratio of dependance.6.The rate of growth of the internal organs is not a process working within itself, but subject to the general conformity to law.7.The growth of the embryo is not the result of an uninterruped developement, but consists of a sequence of increases and depressions.

scholarly journals Weak spatiotemporal response of prey to predation risk in a freely interacting system

2017 ◽  
Author(s):  
Jeremy J. Cusack ◽  
Michel T. Kohl ◽  
Matthew C. Metz ◽  
Tim Coulson ◽  
Daniel R. Stahler ◽  
...  
Keyword(s):  
Predation Risk ◽  
Cervus Elaphus ◽  
Null Model ◽  
Space Use ◽  
Home Ranges ◽  
List Type ◽  
Predator Prey ◽  
Risk Of Predation ◽  
Spatiotemporal Scales ◽  
Spatiotemporal Response

AbstractThe extent to which prey space use actively minimises predation risk continues to ignite controversy. Methodological reasons that have hindered consensus include inconsistent measurements of predation risk, biased spatiotemporal scales at which responses are measured, and lack of robust null expectations.We addressed all three challenges in a comprehensive analysis of the spatiotemporal responses of adult female elk (Cervus elaphus) to the risk of predation by grey wolves (Canis lupus) during winter in northern Yellowstone, USA.We quantified spatial overlap between the winter home ranges of GPS-collared elk and three measures of predation risk: the intensity of wolf space use, the distribution of wolf-killed elk and vegetation openness. We also assessed whether elk varied their use of areas characterised by more or less predation risk across hours of the day, and estimated encounter rates between simultaneous elk and wolf pack trajectories. We determined whether observed values were significantly lower than expected if elk movements were random with reference to predation risk using a null model approach.Although a small proportion of elk did show a tendency to minimise use of open vegetation at specific times of the day, overall we highlight a notable absence of spatiotemporal response by female elk to the risk of predation posed by wolves in northern Yellowstone.Our results suggest that predator-prey interactions may not always result in strong spatiotemporal patterns of avoidance.

scholarly journals Consequences of consumer origin and omnivory on stability in experimental food web modules

2019 ◽  
Author(s):  
Monica Granados ◽  
Katie S. Pagnucco ◽  
Anthony Ricciardi
Keyword(s):  
Food Web ◽  
Coefficient Of Variation ◽  
Species Interactions ◽  
Native Species ◽  
Weak Interactions ◽  
Temporal Stability ◽  
List Type ◽  
Species Identity ◽  
Novel Ecosystem ◽  
Native Populations

AbstractFood web stability, a fundamental characteristic of ecosystems, is influenced by the nature and strength of species interactions. Theory posits that food webs are stabilized by omnivory and disrupted by novel consumers.To test the effects of secondary consumer origin and trophic level on basal resource stability, we constructed crayfish-snail-algae modules using four congeneric species of crayfish (Faxonius spp.), two from native populations (F. propinquus and F. virilis) and two from non-native populations (F. limosus and F. rusticus). We performed surgical manipulations of crayfish feeding structures to create omnivore food web and predator food chain modules. We compared the temporal stability of these modules using measures of the coefficient of variation of the basal resource (benthic algae).Consistent with theoretical and empirical predictions, food web modules with omnivory had the lowest coefficient of variation. However, contrary to prediction, we did not find consistently higher coefficients of variation in modules with non-native species. Rather, across species, we found the lowest coefficient of variation in modules with one of the non-native species (F. rusticus) and one native species (F. virilis), owing to stronger interactions between these crayfish species and their snail and algal food resources.The results suggest that omnivory is indeed stabilizing and that very weak interactions or very low attack rates of the consumer on the basal resource can be unstable. Thus, we demonstrate that omnivores may have different impacts than predators when introduced into a novel ecosystem, differences that can supersede the effect of species identity.

scholarly journals Missense variants in ACE2 are predicted to encourage and inhibit interaction with SARS-CoV-2 Spike and contribute to genetic risk in COVID-19

2020 ◽  
Author(s):  
Stuart A. MacGowan ◽  
Geoffrey J. Barton
Keyword(s):  
Endocytic Pathway ◽  
Spike Protein ◽  
List Type ◽  
Missense Mutations ◽  
Binding Assays ◽  
S Protein ◽  
Missense Variants ◽  
Local Populations ◽  
High Degree ◽  
Protective Variants

AbstractSARS-CoV-2 invades host cells via an endocytic pathway that begins with the interaction of the SARS-CoV-2 Spike glycoprotein (S-protein) and human Angiotensin-converting enzyme 2 (ACE2). Genetic variability in ACE2 may be one factor that mediates the broad-spectrum severity of SARS-CoV-2 infection and COVID-19 outcomes. We investigated the capacity of ACE2 variation to influence SARS-CoV-2 infection with a focus on predicting the effect of missense variants on the ACE2 SARS-CoV-2 S-protein interaction. We validated the mCSM-PPI2 variant effect prediction algorithm with 26 published ACE2 mutant SARS-CoV S-protein binding assays and found it performed well in this closely related system (True Positive Rate = 0.7, True Negative Rate = 1). Application of mCSM-PPI2 to ACE2 missense variants from the Genome Aggregation Consortium Database (gnomAD) identified three that are predicted to strongly inhibit or abolish the S-protein ACE2 interaction altogether (p.Glu37Lys, p.Gly352Val and p.Asp355Asn) and one that is predicted to promote the interaction (p.Gly326Glu). The S-protein ACE2 inhibitory variants are expected to confer a high degree of resistance to SARS-CoV-2 infection whilst the S-protein ACE2 affinity enhancing variant may lead to additional susceptibility and severity. We also performed in silico saturation mutagenesis of the S-protein ACE2 interface and identified a further 38 potential missense mutations that could strongly inhibit binding and one more that is likely to enhance binding (Thr27Arg). A conservative estimate places the prevalence of the strongly protective variants between 12-70 per 100,000 population but there is the possibility of higher prevalence in local populations or those underrepresented in gnomAD. The probable interplay between these ACE2 affinity variants and ACE2 expression polymorphisms is highlighted as well as gender differences in penetrance arising from ACE2’s situation on the X-chromosome. It is also described how our data can help power future genetic association studies of COVID-19 phenotypes and how the saturation mutant predictions can help design a mutant ACE2 with tailored S-protein affinity, which may be an improvement over a current recombinant ACE2 that is undergoing clinical trial.Key results1 ACE2 gnomAD missense variant (p.Gly326Glu) and one unobserved missense mutation (Thr27Arg) are predicted to enhance ACE2 binding with SARS-CoV-2 Spike protein, which could result in increased susceptibility and severity of COVID-193 ACE2 missense variants in gnomAD plus another 38 unobserved missense mutations are predicted to inhibit Spike binding, these are expected to confer a high degree of resistance to infectionThe prevalence of the strongly protective variants is estimated between 12-70 per 100,000 population but higher prevalence may exist in local populations or those underrepresented in gnomADA strategy to design a recombinant ACE2 with tailored affinity towards Spike and its potential therapeutic value is presentedThe predictions were extensively validated against published ACE2 mutant binding assays for SARS-CoV Spike protein

scholarly journals Direct evidence of megamammal-carnivore interaction decoded from bone marks in historical fossil collections from the Pampean region

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3117 ◽  
Author(s):  
Karina Vanesa Chichkoyan ◽  
Borja Figueirido ◽  
Margarita Belinchón ◽  
José Luis Lanata ◽  
Anne-Marie Moigne ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Popular Media ◽  
South American ◽  
Long Bones ◽  
Ecological Interactions ◽  
Predator Prey ◽  
Ecological Relationships ◽  
Pampean Region ◽  
Fossil Bones ◽  
Crucial Information

Pleistocene South American megafauna has traditionally attracted the interest of scientists and the popular media alike. However, ecological interactions between the species that inhabited these ecosystems, such as predator-prey relationships or interspecific competition, are poorly known. To this regard, carnivore marks imprinted on the fossil bones of megamammal remains are very useful for deciphering biological activity and, hence, potential interspecific relationships among taxa. In this article, we study historical fossil collections housed in different European and Argentinean museums that were excavated during the 19th and early 20th centuries in the Pampean region, Argentina, in order to detect carnivore marks on bones of megamammals and provide crucial information on the ecological relationships between South American taxa during the Pleistocene. Our results indicate that the long bones of megafauna from the Pampean region (e.g., the Mylodontidae and Toxodontidae families) exhibit carnivore marks. Furthermore, long bones of medium-sized species and indeterminate bones also present punctures, pits, scores and fractures. Members of the large-carnivore guild, such as ursids, canids and even felids, are recognised as the main agents that inflicted the marks. We hypothesize that the analysed carnivore marks represent the last stages of megaherbivore carcass exploitation, suggesting full consumption of these animals by the same or multiple taxa in a hunting and/or scavenging scenario. Moreover, our observations provide novel insights that help further our understanding of the palaeoecological relationships of these unique communities of megamammals.

Mammalian Faunal Dynamics of the Great American Interchange: Reply to an Alternative Interpretation

Paleobiology ◽  
1978 ◽  
Vol 4 (2) ◽  
pp. 206-209 ◽  
Author(s):  
S. David Webb
Keyword(s):  
Alternative Interpretation ◽  
Early Pleistocene ◽  
List Type ◽  
South American ◽  
Type Number ◽  
Community Evolution

In their “alternative interpretation” Marshall and Hecht raise two interesting questions: I)Is “Taxocene Analysis” a permissible approach to community evolution, and if so under what conditions?II)What really happened to the ten South American ungulate genera that vanished during the Early Pleistocene?As these are fundamentally different questions, I shall consider each separately.

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