Tonic Immobility Is Influenced by Starvation, Life Stage, and Body Mass in Ixodid Ticks

Abstract The ability to escape predation modulates predator–prey interactions and represents a crucial aspect of organismal life history, influencing feeding, mating success, and survival. Thanatosis, also known as death feigning or tonic immobility (TI), is taxonomically widespread, but understudied in blood-feeding vectors. Hematophagous arthropods, such as ticks, are unique among animals as their predators (birds, mice, lizards, frogs, and other invertebrates) may also be their source of food. Therefore, the trade-off between predator avoidance and host-seeking may shift as the time since the last bloodmeal increases. Because ticks are slow-moving and unable to fly, or otherwise escape, we predicted that they may use TI to avoid predation, but that TI would be influenced by time since the last bloodmeal (starvation). We therefore aimed to quantify this relationship, examining the effect of starvation, body mass, and ontogeny on TI for two tick species: Dermacentor variabilis (Say) (Acari: Ixodidae) and Rhipicephalus sanguineus (Latreille) (Acari: Ixodidae). As we predicted, the duration and use of TI decreased with time since feeding and emergence across species and life stages. Therefore, ticks may become more aggressive in their search for a bloodmeal as they continue to starve, opting to treat potential predators as hosts, rather than avoiding predation by feigning death. Antipredator behaviors such as TI may influence the intensity and amount of time ticks spend searching for hosts, driving patterns of tick-borne pathogen transmission. This identification and quantification of a novel antipredation strategy add a new component to our understanding of tick life history.

Download Full-text

Modulation of odour-guided behaviour in mosquitoes

Cell and Tissue Research ◽

10.1007/s00441-020-03368-6 ◽

2021 ◽

Vol 383 (1) ◽

pp. 195-206

Author(s):

Sharon R. Hill ◽

Rickard Ignell

Keyword(s):

Functional Genomics ◽

Life Stage ◽

Blood Feeding ◽

Model Systems ◽

Extrinsic Factors ◽

Intrinsic Factors ◽

Host Seeking ◽

Enhancing Resources ◽

Maturation Age ◽

Behavioural Repertoire

AbstractMosquitoes are emerging as model systems with which to study innate behaviours through neuroethology and functional genomics. Decades of work on these disease vectors have provided a solid behavioural framework describing the distinct repertoire of predominantly odour-mediated behaviours of female mosquitoes, and their dependence on life stage (intrinsic factors) and environmental cues (extrinsic factors). The purpose of this review is to provide an overview of how intrinsic factors, including adult maturation, age, nutritional status, and infection, affect the attraction to plants and feeding on plant fluids, host seeking, blood feeding, supplemental feeding behaviours, pre-oviposition behaviour, and oviposition in female mosquitoes. With the technological advancements in the recent two decades, we have gained a better understanding of which volatile organic compounds are used by mosquitoes to recognise and discriminate among various fitness-enhancing resources, and characterised their neural and molecular correlates. In this review, we present the state of the art of the peripheral olfactory system as described by the neural physiology, functional genomics, and genetics underlying the demonstrated changes in the behavioural repertoire in female mosquitoes. The review is meant as a summary introduction to the current conceptual thinking in the field.

Download Full-text

"Heat waves" experienced during larval life have species-specific consequences on life-history traits and sexual development in anuran amphibians

10.1101/2021.12.17.473144 ◽

2021 ◽

Author(s):

Janos Ujszegi ◽

Reka Bertalan ◽

Nikolett Ujhegyi ◽

Viktoria Verebelyi ◽

Edina Nemeshazi ◽

...

Keyword(s):

Life History ◽

Larval Development ◽

Body Mass ◽

Sexual Development ◽

Life History Traits ◽

Heat Waves ◽

Life Stage ◽

Bufo Bufo ◽

Negative Consequences ◽

Cold Adapted

Extreme temperatures during heat waves can induce mass-mortality events, but can also exert sublethal negative effects by compromising life-history traits and derailing sexual development. Ectothermic animals may, however, also benefit from increased temperatures via enhanced physiological performance and the suppression of cold-adapted pathogens. Therefore, it is crucial to address how the intensity and timing of naturally occurring or human-induced heat waves affect life-history traits and sexual development in amphibians, to predict future effects of climate change and to minimise risks arising from the application of elevated temperature in disease mitigation. We raised agile frog (Rana dalmatina) and common toad (Bufo bufo) tadpoles at 19 °C and exposed them to a simulated heat wave of 28 or 30 °C for six days during one of three ontogenetic periods (early, mid or late larval development). In agile frogs, exposure to 30 °C during early larval development increased mortality. Regardless of timing, all heat-treatments delayed metamorphosis, and exposure to 30 °C decreased body mass at metamorphosis. Furthermore, exposure to 30 °C during any period and to 28 °C late in development caused female-to-male sex reversal, skewing sex ratios strongly towards males. In common toads, high temperature only slightly decreased survival and did not influence phenotypic sex ratio, while it reduced metamorph mass and length of larval development. Juvenile body mass measured two months after metamorphosis was not adversely affected by temperature treatments in either species. Our results indicate that heat waves may have devastating effects on amphibian populations, and the severity of these negative consequences, and sensitivity can vary greatly between species and with the timing and intensity of heat. Finally, thermal treatments against cold-adapted pathogens have to be executed with caution, taking into account the thermo-sensitivity of the species and the life stage of animals to be treated.

Download Full-text

Advances in Understanding Vector Behavioural Traits after Infection

Pathogens ◽

10.3390/pathogens10111376 ◽

2021 ◽

Vol 10 (11) ◽

pp. 1376

Author(s):

Nouman Javed ◽

Asim Bhatti ◽

Prasad N. Paradkar

Keyword(s):

Management Strategies ◽

Blood Feeding ◽

Pathogen Transmission ◽

Bed Nets ◽

Host Feeding ◽

Transmission Potential ◽

Disease Epidemiology ◽

Behavioural Changes ◽

Host Seeking ◽

Vector Borne

Vector behavioural traits, such as fitness, host-seeking, and host-feeding, are key determinants of vectorial capacity, pathogen transmission, and epidemiology of the vector-borne disease. Several studies have shown that infection with pathogens can alter these behavioural traits of the arthropod vector. Here, we review relevant publications to assess how pathogens modulate the behaviour of mosquitoes and ticks, major vectors for human diseases. The research has shown that infection with pathogens alter the mosquito’s flight activity, mating, fecundity, host-seeking, blood-feeding, and adaptations to insecticide bed nets, and similarly modify the tick’s locomotion, questing heights, vertical and horizontal walks, tendency to overcome obstacles, and host-seeking ability. Although some of these behavioural changes may theoretically increase transmission potential of the pathogens, their effect on the disease epidemiology remains to be verified. This study will not only help in understanding virus–vector interactions but will also benefit in establishing role of these behavioural changes in improved epidemiological models and in devising new vector management strategies.

Download Full-text

Exploiting assembly pheromone for the control of ixodid ticks

Acarologia ◽

10.24349/acarologia/20184254 ◽

2018 ◽

Vol 58 (2) ◽

pp. 471-482

Author(s):

R.S. Ranju ◽

Bhaskaran Ravi Latha ◽

V. Leela

Keyword(s):

Tick Species ◽

Life Stage ◽

Effective Means ◽

Rhipicephalus Sanguineus ◽

Positive Control ◽

Negative Control ◽

Ixodid Ticks ◽

Assembly Pheromone ◽

Larval Stages

The effect of an Assembly Pheromone – Deltamethrin complex (AP – D complex) on the larvae of five ixodid tick species viz. Rhipicephalus sanguineus, R. microplus, R. haemaphysaloides, Hyalomma marginatum and Haemaphysalis bispinosa, as well as the adults of R. sanguineus and R. microplus, was assessed by in vitro bioassays. All the larval as well as adult stages of ticks exposed to the AP – D complex were lured and killed within 24 hours of exposure, except H. bispinosa. Exposure to the AP – D complex for an hour resulted in 70%, 95%, 90%, 90%, 95% mortality of the larval stages of Rhipicephalus sanguineus, R. microplus, R. haemaphysaloides, H. bispinosa and H. marginatum respectively. No mortality was observed when the larval stages of the five tick species were exposed to AP alone (positive control). Exposure of adults to the AP – D complex for an hour resulted 92% and 90% mortality of R. microplus and R. sanguineus, respectively. Negligible mortality was recorded in adult ticks exposed to deltamethrin alone (Negative control), while no mortality was recorded when exposed only to AP (Positive control). Hence, the AP – D complex is better in luring and killing ticks than AP or D alone, regardless of the life stage. Our results suggest that the development of a sustained release AP – D complex device may be an effective means of controlling ticks in India.

Download Full-text

Comparative Microbiome Profiles of Sympatric Tick Species from the Far-Western United States

Insects ◽

10.3390/insects10100353 ◽

2019 ◽

Vol 10 (10) ◽

pp. 353 ◽

Cited By ~ 8

Author(s):

Betsabel Chicana ◽

Lisa I. Couper ◽

Jessica Y. Kwan ◽

Enxhi Tahiraj ◽

Andrea Swei

Keyword(s):

United States ◽

Tick Species ◽

Life Stage ◽

Dermacentor Variabilis ◽

Pathogen Transmission ◽

Western United States ◽

Microbial Composition ◽

Host Preferences ◽

Microbial Species ◽

Tick Microbiome

Insight into the composition and function of the tick microbiome has expanded considerably in recent years. Thus far, tick microbiome studies have focused on species and life stages that are responsible for transmitting disease. In this study we conducted extensive field sampling of six tick species in the far-western United States to comparatively examine the microbial composition of sympatric tick species: Ixodes pacificus, Ixodes angustus, Dermacentor variabilis, Dermacentor occidentalis, Dermacentor albipictus, and Haemaphysalis leporispalustris. These species represent both common vectors of disease and species that rarely encounter humans, exhibiting a range of host preferences and natural history. We found significant differences in microbial species diversity and composition by tick species and life stage. The microbiome of most species examined were dominated by a few primary endosymbionts. Across all species, the relative abundance of these endosymbionts increased with life stage while species richness and diversity decreased with development. Only one species, I. angustus, did not show the presence of a single dominant microbial species indicating the unique physiology of this species or its interaction with the surrounding environment. Tick species that specialize in a small number of host species or habitat ranges exhibited lower microbiome diversity, suggesting that exposure to environmental conditions or host blood meal diversity can affect the tick microbiome which in turn may affect pathogen transmission. These findings reveal important associations between ticks and their microbial community and improve our understanding of the function of non-pathogenic microbiomes in tick physiology and pathogen transmission.

Download Full-text

Supercooling Points of Adult Dermacentor variabilis (Acari: Ixodidae) From a Population Near the Northern Distribution Limit

Journal of Medical Entomology ◽

10.1093/jme/tjaa223 ◽

2020 ◽

Author(s):

Matthew E M Yunik ◽

Neil B Chilton

Keyword(s):

Cold Hardiness ◽

Dermacentor Variabilis ◽

Subzero Temperatures ◽

Host Seeking ◽

Short Period ◽

Significant Difference ◽

Northern Distribution ◽

Dog Tick ◽

Provincial Park ◽

Established Population

Abstract The northern distributional limit of Dermacentor variabilis Say, the American dog tick, is expanding in Saskatchewan and Manitoba (western Canada). The ability of D. variabilis to continue to expand its range northwards will depend upon the ability of individuals within populations at the species distributional edge to withstand very low temperatures during winter. One component of cold hardiness is the supercooling point (SCP), the temperature below 0°C at which an individual freezes. In this study, the SCP was determined for 94 questing D. variabilis adults (44 females and 50 males) from an established population near Blackstrap Provincial Park in Saskatchewan. SCP values ranged from −18.2 to −6.7°C, with a median of −13.3°C. This suggests that host-seeking D. variabilis adults differ in their ability to survive exposure to subzero temperatures, for at least a short period of time, without freezing. The distribution of SCPs was bimodal, but there was no significant difference in SCP values between female and male ticks, and no relationship between SCP and tick body weight. It remains to be determined what factors contribute to the variation in SCP values among questing D. variabilis adults.

Download Full-text

Tick Ecdysteroid Hormone, Global Microbiota/Rickettsia Signaling in the Ovary versus Carcass during Vitellogenesis in Part-Fed (Virgin) American Dog Ticks, Dermacentor variabilis

Microorganisms ◽

10.3390/microorganisms9061242 ◽

2021 ◽

Vol 9 (6) ◽

pp. 1242

Author(s):

Loganathan Ponnusamy ◽

Haley Sutton ◽

Robert D. Mitchell ◽

Daniel E. Sonenshine ◽

Charles S. Apperson ◽

...

Keyword(s):

Hormonal Regulation ◽

Natural Populations ◽

Blood Feeding ◽

Dermacentor Variabilis ◽

Transovarial Transmission ◽

Rickettsia Species ◽

Adult Females ◽

Dog Tick ◽

Total Bacteria

The transovarial transmission of tick-borne bacterial pathogens is an important mechanism for their maintenance in natural populations and transmission, causing disease in humans and animals. The mechanism for this transmission and the possible role of tick hormones facilitating this process have never been studied. Injections of physiological levels of the tick hormone, 20-hydroxyecdysone (20E), into part-fed (virgin) adult females of the American dog tick, Dermacentor variabilis, attached to the host caused a reduction in density of Rickettsia montanensis in the carcass and an increase in the ovaries compared to buffer-injected controls. This injection initiates yolk protein synthesis and uptake by the eggs but has no effect on blood feeding. Francisella sp. and R. montanensis were the predominant bacteria based on the proportionality in the carcass and ovary. The total bacteria load increased in the carcass and ovaries, and bacteria in the genus Pseudomonas increased in the carcass after the 20E injection. The mechanism of how the Rickettsia species respond to changes in tick hormonal regulation needs further investigation. Multiple possible mechanisms for the proliferation of R. montanensis in the ovaries are proposed.

Download Full-text

Implications of diet on mosquito life history traits and pathogen transmission

Environmental Research ◽

10.1016/j.envres.2021.110893 ◽

2021 ◽

Vol 195 ◽

pp. 110893

Author(s):

Laura Carvajal-Lago ◽

María José Ruiz-López ◽

Jordi Figuerola ◽

Josué Martínez-de la Puente

Keyword(s):

Life History ◽

Life History Traits ◽

Pathogen Transmission

Download Full-text

Host behaviour, age and sex correlate with ectoparasite prevalence and intensity in a colonial mammal, the little brown bat

Behaviour ◽

10.1163/1568539x-00003233 ◽

2014 ◽

Vol 152 (1) ◽

pp. 83-105 ◽

Cited By ~ 17

Author(s):

Quinn M.R. Webber ◽

Liam P. McGuire ◽

Steven B. Smith ◽

Craig K.R. Willis

Keyword(s):

Pathogen Transmission ◽

Myotis Lucifugus ◽

Physical Contact ◽

Wildlife Diseases ◽

Colonial Species ◽

Host Seeking ◽

Host Sex ◽

Little Brown Bat ◽

Host Behaviour ◽

Age And Sex

The influence of behaviour on host-parasite dynamics has theoretical support but few empirical studies have examined this influence for wild-captured hosts, especially in colonial species, which are thought to face generally high risk of exposure. Behavioural tendencies of hosts in novel environments could mediate host exposure. We tested the hypothesis that behavioural tendencies of hosts, and host sex and age, correlate with prevalence and intensity of ectoparasites in a gregarious mammal, the little brown bat (Myotis lucifugus). We also tested whether relationships between host behaviour and parasite prevalence and intensity would vary between taxa of ectoparasites which differ in host-seeking behaviour. We predicted that individual hosts displaying active and explorative behaviours would have higher prevalence and intensity of parasites that depend on physical contact among hosts for transmission (mites) but that host behaviour would not influence prevalence and intensity of mobile ectoparasites with active host-seeking behaviour (fleas). We recorded behavioural responses of wild-captured bats in a novel-environment test and then sampled each individual for ectoparasites. After accounting for age and sex we found mixed support for our hypotheses in some but not all demographics. More active adult and young of the year (YOY) males were more likely to host mites while more active adult and YOY females were less likely to host fleas. Our results highlight possible differences in the influence of host and parasite behaviour on parasite transmission dynamics for colonial compared to non-colonial species and have conservation implications for understanding pathogen transmission in bat white-nose syndrome and other wildlife diseases.

Download Full-text

THE DISTRIBUTION OF RICKETTSIA IN THE TISSUES OF INSECTS AND ARACHNIDS

Journal of Experimental Medicine ◽

10.1084/jem.37.4.431 ◽

1923 ◽

Vol 37 (4) ◽

pp. 431-456 ◽

Cited By ~ 37

Author(s):

E. V. Cowdry

Keyword(s):

Rhipicephalus Sanguineus ◽

Dermacentor Variabilis ◽

Animal Products ◽

Gram Negative ◽

Pediculus Humanus ◽

Larval Stages ◽

Pulex Irritans ◽

Boophilus Decoloratus ◽

Occasional Occurrence ◽

Definition Of

In the absence of a satisfactory definition of Rickettsia the observations herein recorded were arbitrarily limited to bacterium-like organisms which are intracellular and Gram-negative. Rickettsia of this type were found in the following species: Amblyomma americana, Amblyomma hebræum, Boophilus decoloratus, Atomus sp., Casinaria infesta, Chrysopa oculata, Ctenocephalus canis, Dermacentor variabilis, Lepisma saccharina, Lucoppia curviseta, Margaropus annulatus, Margaropus annulatus australis, Ornithodoros turicata, Pulex irritans, Rhipicephalus sanguineus, Rhipicephalus evertsi, and Salticus scenicus. Since intracellular, Gram-negative Rickettsia have been recorded in the literature as existing in Cimex lectularius, Dermacentor venustus, Melophagus ovinus, and Pediculus humanus, the occasional occurrence of such bodies must be conceded in the following groups not closely related phylogenetically: Attidæ, Trombidiidæ, Argasidæ, lxodidæ, Cinura, Acanthiidæ, Pediculidæ, Hippoboscidæ, Chrysopidæ, Pulicidæ, and Ichneumonidæ. The species which harbor Rickettsia differ widely in diet and habitat. One such species is insectivorous throughout life, two are insectivorous in larval stages, becoming vegetarian in the adult condition, one is chiefly vegetarian but partakes of some animal products, and two are usually entirely vegetarian; while the remainder subsist wholly upon a diet of mammalian blood. Rickettsia are associated, in only a few cases, with diseases in mammals. The evidence at hand does not lead beyond the conclusion that the Rickettsia mentioned above are true Gram-negative microorganisms, easily distinguishable from mitochondria and all other cytoplasmic and nuclear granulations, rather completely adapted to an intracellular existence, exhibiting in some cases a remarkable degree of host specificity, and often inherited through the eggs.

Download Full-text