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First published online May 1, 2009
Journal of Experimental Biology 212, 1436-1441 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.028951
Increased locomotor activity and metabolism of Aedes aegypti infected with a life-shortening strain of Wolbachia pipientis
1 School of Biological Sciences, The University of Queensland, St Lucia,
Queensland, 4072, Australia
2 Information Technology Services, The University of Queensland, St Lucia,
Queensland, 4072, Australia
3 Sansom Institute, University of South Australia, GPO Box 2471, Adelaide, South
Australia, 5001, Australia
* Author for correspondence (e-mail: e.mcgraw{at}uq.edu.au)
Accepted 3 March 2009
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Summary |
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 TOP Summary INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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Key words: Aedes aegypti, Wolbachia pipientis, locomotor activity, metabolic rate, insect
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INTRODUCTION |
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TOPSummaryINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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;
Ijichi et al., 2002). Because
the microbe is transmitted maternally through the egg, both somatic tissue
infection in females and the infection of males are effectively a dead end for
the microbe. While most research has understandably focused on the ability of
Wolbachia to manipulate host reproduction, there is growing evidence
that the infection may have additional consequences for hosts. For example, in
the parasitoid wasp Leptopilina heterotoma
(Fleury et al., 2000),
Wolbachia decreases locomotor activity, whereas in
Drosophila it can either increase or decrease activity, depending on
the host species and the infecting Wolbachia strain
(Peng et al., 2008). The
underlying causes of these infection-induced effects are not known, but may
include Wolbachia-induced pathogenesis, effects on local cellular and
tissue function, and/or changes in energetic demands.
The Wolbachia strain wMelPop, first identified in
Drosophila melanogaster, shortens adult lifespan
(Min and Benzer, 1997). Unlike
most other Wolbachia infections, wMelPop acts more like a
traditional bacterial pathogen than an intracellular symbiont. Insects
infected with wMelPop survive roughly half as long as uninfected
counterparts and premature death is thought to be caused by bacterial
over-replication leading to local cell rupture and tissue damage
(McGraw et al., 2002;
McMeniman et al., 2008;
Min and Benzer, 1997;
Reynolds et al., 2003).
Recently, the mosquito disease vector Aedes aegypti was artificially
infected with this strain of Wolbachia as the first step in
developing a biocontrol strategy. The goal of the strategy is to shift
mosquito population age structure such that it leads to a reduction in human
pathogen transmission (Brownstein et al.,
2003; McMeniman et al.,
2009). This approach takes advantage of the extrinsic incubation
period (EIP) or the delay in time between when an insect consumes a
pathogen-infected blood meal and when it can actively transmit the agent in
subsequent feeding. This time window varies depending on the
host–pathogen association as dictated by developmental constraints of
the pathogen and/or the process of pathogen migration from the gut to the
salivary glands (Brownstein et al.,
2003). The result of this EIP is that only older individuals in
vector populations transmit disease. As such, premature insect death caused by
Wolbachia infection has the potential to significantly reduce the
transmission of insect-transmitted pathogens like dengue viruses.
The potential success of a wMelPop-based biocontrol strategy
hinges upon a range of other factors in the insect–microbe association.
Firstly, as for all infectious agent or genetic modification strategies, the
altered insects must be competitive in the field when compared with wild
counterparts. This requirement is buffered somewhat by the action of
cytoplasmic incompatibility (CI), a reproductive manipulation caused by
Wolbachia. The expression of CI is predicted to aid in the spread of
Wolbachia even when the infection confers moderate reductions in host
fitness (O'Neill et al., 1997;
Turelli, 1994). Secondly, the
introduced symbiont must not inadvertently enhance the transmission efficiency
of vectored disease agents. Simply reducing the number of old age individuals
in the population is not sufficient if the infection simultaneously improves
mosquito vector competence. In Ae. aegypti, wMelPop has already been
shown to cause life shortening and strong CI
(McMeniman et al., 2009). The
further progression of this biocontrol strategy, however, requires a broader
understanding of the microbe's effects on host biology that might impact on
fitness and vectorial capacity.
In mosquitoes, locomotor activity underpins the activities of locating mates, suitable hosts for feeding, resting places for blood meal digestion and finally oviposition sites. Changes in these behaviours could substantially affect both the transinfected mosquito's competitiveness in the field and its capacity to transmit disease. Here we report the results of a study aimed at determining whether wMelPop alters the locomotor activity of Ae. aegypti. Behavioural observations were made over three adult mosquito ages in an attempt to capture the progression of wMelPop pathogenesis in the host. We also measured, in parallel experiments, the carbon dioxide production of the mosquitoes to examine the effect of Wolbachia infection on metabolic rate. Our expectation was that the infected mosquitoes would demonstrate decreased activity and a corresponding decrease in metabolic rate, due to energetic drain or bacterial pathogenicity. Both trends were expected to intensify as the insect aged and Wolbachia pathogenesis advanced.
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MATERIALS AND METHODS |
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TOPSummaryINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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). In
brief, the Wolbachia strain wMelPop, native to
Drosophila melanogaster (Min and
Benzer, 1997), was transferred into Ae. aegypti by
embryonic microinjection. Descendants of this isofemale line were outcrossed
for several generations to the original recipient line of mosquitoes and
selected for stable infection before closing the colony. At generations 8 and
9 post-transinfection, an aposymbiotic control line was created by antibiotic
treatment of the Wolbachia-infected line
(McMeniman et al., 2009). All
experiments reported here were carried out on mosquitoes at generations
14–16 post-transinfection (i.e. 4–6 generations post-treatment),
with replicates representing different generations. Mosquitoes were reared
under standard conditions (25°C, 12 h:12 h L:D, 80% relative humidity, RH)
(Gerberg et al., 1994). Larvae
were reared in plastic trays at a density of 150 per 3 l of water and supplied
with a daily dose of 0.15 g TetraMin aquarium fish food (Tetra, Melle,
Germany). Adults were separated by sex and maintained as virgins in cages (30
cmx30 cmx30 cm) of 
150 individuals. Adults were supplied with
a basic diet of 10% sucrose solution administered through cotton pledgets. The
adult ages of 3, 15 and 25 days were selected to represent the periods when
100%, 90% and 20% of the wMelPop-infected population were
still surviving, respectively (McMeniman
et al., 2009).
Video recording of mosquito locomotion
Our locomotor assay was based on several previously published models
(Allemand et al., 1994;
Bonatz et al., 1987;
Grobbelaar et al., 1967;
Kawada and Takagi, 2004;
Liseichikov and Zakharevskii,
1978; Mankin,
1994; Reynolds and Riley,
2002; Rowley et al.,
1987; Sbalzarini and
Koumoutsakos, 2005), but was most heavily influenced by Williams
and Kokkinn (Williams and Kokkinn,
2005). Mosquitoes were placed in an observation chamber
(Fig. 1) during experiments and
their motion captured via a video camera. The observation chamber
(Fig. 1) was constructed using
white (sides and back) and transparent Perspex (front pane) and contained
distinct cells that allowed for the simultaneous observation of 10 individual
mosquitoes, one per cell. Mosquitoes were provided with 10% sucrose solution
ad libitum during observation periods, dispensed through dental
cotton wicks (1xØ0.5 cm). The wicks placed in each observation
cell also provided constant humidity (80–85% RH). Mosquitoes were
transferred from rearing cages to observation chambers 20 min prior to
recording of activity to allow them to adapt to the new environment. Recording
began daily at 14:30 h, was paused during the hours of darkness
(21:00–07:00 h) and was completed at 12:30 h the following day to allow
time to transfer in the next set of mosquitoes. After each observation period
mosquitoes were aspirated out of the chamber and killed. The chambers were
cleaned with ethanol (80%) and the food supply replaced prior to subsequent
observation periods. No mosquito mortality was observed during the
observations. A total of three replicates each of 10 mosquitoes were studied
per sexxstrainxage per study chamber.
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A two-colour camera (DR2-13S2m/C-CS, Point Grey Research, Vancouver, BC, Canada) was fitted with a CCTV lens (12VM412ASIR, Tamron, Commack, NY, USA) and fixed on a mounting bracket 110 cm from the chamber. The distance of the camera to the object, the zoom, and the focus and iris aperture was optimized to reduce barrelling and distortion of images. A flat source light was placed 10 cm behind the chamber, which provided sufficient lighting for the camera sensor to capture high quality images but did not increase ambient temperatures. The light source power switch was synchronized with the room lights using a timer. The entire experimental setup was enclosed in cardboard to minimize intrusion of additional stimuli.
The file format used for recording, Audio Video Interleave (AVI), is
limited to a maximum size of 2 GB, which amounted to approximately 8 min of
video footage. To obtain a continuous video recording, we developed a program
called Mossiecap in Matlab (Mathworks, Inc., Natick, MA, USA) that recorded
multiple sequential 1.5 GB AVI files. This file size captured 6 min of video
(i.e. 10 files=60 min) at 12 framess–1. Each day's footage
(420 GB) was recorded onto an external hard drive connected to a desktop
computer. The contents of each hard drive were then transferred to the
hierarchical storage management (HSM) system at The University of Queensland.
Video files stored on the HSM were then evenly distributed to local disks on
20 workstations located in the Visualization and Advanced Computing (ViSAC)
laboratories at The University of Queensland. Mossiefly, a custom-designed
program developed in Matlab was used to process videos for motion detection
and tracking. This program detected and tracked movement (walking and flying
separately) of individual mosquitoes and digitized the coordinates and time
for each movement. The files containing data from movement detection were then
analysed using Mossiestat, a program developed in Matlab that summarized the
movement data captured with Mossiefly into numerical values used for
statistical analysis. A total measure of activity (summation of time spent
flying and walking) reported per hour was used for all subsequent statistical
analysis as it was more informative than examining the variables
independently.
Metabolic rate
Closed-system respirometry was used to measure CO2 production
(
CO2) in the mosquitoes.
CO2 production has been shown extensively to be an accurate measure
of metabolism for small and highly aerobic organisms such as insects
(Lighton, 1991;
Lighton and Duncan, 2002;
Van Voorhies et al., 2004).
Our experiment was designed to determine whether metabolic rate was
significantly different between wMelPop-infected and uninfected
mosquitoes in each of two daytime intervals lasting 4 h. Fifteen individual
mosquitoes were measured for each sexxstrainxagexinterval
combination. These measurements were replicated 3 times. Mosquitoes were
discarded after the recording interval and replaced with fresh mosquitoes from
the same rearing cage.
An ADInstruments (Sydney, Australia) gas analyzer (ML205) and a PowerLab (85P) analog-to-digital converter connected to a computer running data acquisition software (ADInstruments, Chart 5) were used to measure CO2 production from mosquitoes. Before each experiment, the gas analyser was calibrated with gas of a known CO2 content. Individual mosquitoes were loaded into 25 ml syringes, mounted with a three-way valve stopcock. Before the three-way valve was closed the syringe was carefully flushed with room air to remove possible CO2 traces. Immediately after the 15 syringes were closed, a separate syringe was filled with air and kept as a control sample for initial room air CO2 concentration. After the 4 h interval, the syringes were injected into the gas analyser at 2 ml s–1 until 5 ml of air remained. The gas concentrations for each mosquito were used to calculate mosquito metabolic rate. The dry mass of each mosquito was obtained after freezing them for 48 h at –20°C and desiccating the tissue in a dry vacuum pump. Dry mass was measured with an electronic balance (Sartorius bp211D; Goettingen, Germany) to the nearest 0.01 mg. Mosquitoes were not weighed before metabolic rate experiments because immobilization methods (i.e. CO2 asphyxiation) may alter metabolic rate.
The following formulas based on those of Bartholomew and colleagues
(Bartholomew et al., 1985) were
used for calculation of metabolic rate (ml CO2
h–1):
 | (1) |
):
 | (2) |
is the mean mass of male and
female mosquitoes used for each of the metabolic experiments, and M
is the mass of individual mosquitoes. This formula assumes that CO2
production is proportional to mass0.75
(West et al., 2002).
Statistical analysis
Transformations (square root) of the activity measures and the scaled
metabolic rate were necessary to generate normal distributions. General linear
models were then constructed in Statistica Release 8 (StatSoft;
www.statsoft.com)
for each of the sexes separately to explore the effects of age, infection
status, time of day and replicate on each of the activity and metabolic rate
datasets separately. Student's t-tests were then employed to
specifically test for differences in metabolic rate between infected and
uninfected mosquitoes at each of the three ages.
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RESULTS |
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TOPSummaryINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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DISCUSSION |
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TOPSummaryINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
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The direct negative effects of antibiotic treatment on the insect and the
role of genetic drift during breeding can potentially limit the capacity of
uninfected lines to serve as true controls in studies like this one.
Tetracycline treatment has been shown to cause reductions in the density of
mitochondria in Drosophila that can last for several generations
post-treatment (Ballard and Melvin,
2007). The mosquitoes in this study were therefore reared for
4–6 generations post-treatment prior to experimentation to minimize any
such effects on the physiological phenotypes measured. The process of
antibiotic treatment, aside from clearing insects of Wolbachia, has
the added consequence of removing microbial gut flora. In mosquitoes,
re-colonization of gut flora in the control line should not be a major issue
given that the larval phase is subsequently reared in a microbial-rich aquatic
environment parallel to that of the infected line. Lastly, experiments were
conducted within 6 generations of antibiotic curing and at each generation the
effective population size was kept large to minimize drift effects.
Our initial expectation was that wMelPop would act like a
traditional bacterial pathogen. While little is known about the behavioural
responses of mosquitoes with systemic bacterial infections, experiments in
Drosophila melanogaster lend some predictions about infection and
insect activity. In the case of Streptococcus pneumoniae and
Listeria monocytogenes, infected flies exhibit altered circadian
rhythms, but no real change in total activity in a day
(Shirasu-Hiza et al., 2007).
Infected flies exhibit more homogeneous patterns of activity, without
pronounced peaks and troughs. Whether this change in activity is the direct
result of bacterial virulence or an unintended result of the host immune
response is still not known (Shirasu-Hiza
and Schneider, 2007). This model, however, does not describe the
behaviour of wMelPop-infected Ae. aegypti, as their activity
patterns, while elevated, were largely parallel to those of uninfected
mosquitoes. The wMelPop-infected mosquitoes did not appear to have
altered circadian rhythms. Further examination of infected mosquitoes during
the night-time are required to assess patterns of activity over a 24 h
cycle.
Wolbachia infections are highly dispersed throughout host tissues,
with their exact tissue distribution and density dependent on both the host
and Wolbachia strain (Dobson et
al., 1999; Ijichi et al.,
2002). It is possible that Wolbachia infections in these
diverse somatic tissues underlie the changes in activity or metabolism seen
here. In the original characterization of wMelPop in Drosophila
melanogaster, the bacteria were thought to over-replicate, most
dramatically in nervous and muscle tissues
(Min and Benzer, 1997). It is
conceivable that local changes or damage in the cells of these tissues could
be affecting higher-level physiological functions and behaviour. The effects
we see could simply be the unintended consequence of somatic tissue
infection.
The genome sequence of the wMel strain revealed that, as expected
for an endosymbiont, Wolbachia does not contain the complete set of
metabolic pathways possessed by free-living bacteria
(Wu et al., 2004). In
particular it can utilize only a limited number of substrates and is able to
synthesize very few metabolic intermediates. Considered an amino acid
heterotroph, the microbe probably obtains most of its energy by importing
amino acids directly from the host. Wolbachia's drain on host
resources, especially in the case of wMelPop where the infection
titre is high, may lead to increased energy demands. The activity seen in the
infected mosquito may simply reflect more frequent trips to the sugar water
source present in the cells. Increases in such food-seeking activities could
also drive increases in metabolism
(Delthier, 1976), although this
does not seem likely as peak patterns in activity and metabolic rate do not
coincide (3 days versus 15 days of age, respectively). If infected
mosquitoes are indeed hungrier, one would predict quantifiable increases in
sugar water and blood meal consumption in the presence of infection.
The last explanation that encompasses the increases in both metabolic rate
and activity is that wMelPop-infected mosquitoes are experiencing
accelerated senescence, in effect living faster and dying younger. Tradeoffs
between metabolic rate and lifespan have long been proposed in insects, but
most evidence from Drosophila suggests such relationships do not
exist (Hulbert et al., 2004;
Van Voorhies et al., 2003;
Van Voorhies et al., 2004).
The shortened lifespan of wMelPop-infected D. melanogaster
has always been attributed to local tissue death and destruction caused by
bacterial over-replication, but the direct relationship between bacterial
density and death may not be the same in Ae. aegypti (A. W. C. Fong,
personal communication). Until the pathology of the wMelPop infection
is better understood in Ae. aegypti it will not be clear whether the
phenotypes of shortened lifespan and higher metabolic rate and activity are
related. One challenge to dissecting these relationships is that, as
wMelPop-infected individuals age and become sicker, it becomes
increasingly difficult to partition the direct effects of Wolbachia
on hosts from the generalized death process. Examining the pathology of
wMelPop in middle-aged mosquitoes, well before the onset of death,
may therefore be most informative.
The effect of the wMelPop infection on activity has now been
measured in D. melanogaster, D. simulans
(Peng et al., 2008) and
Ae. aegypti. In D. melanogaster, wMelPop behaves like
another native and benign infection, wMel, in reducing host activity
across the insect's lifespan. This suggests the activity changes are caused
simply by the presence of Wolbachia, rather than by any density-based
effects or by increasing pathogenesis near death. D. simulans
artificially transinfected with wMelPop exhibits only marginal
increases in activity in very old hosts, whereas the native infection
wRi has the capacity to vastly increase host activity at all ages
studied (Peng et al., 2008).
Interestingly, the wRi strain also confers greater fecundity to its
host (Weeks et al., 2007) and
its spreading capacity in wild populations is well documented
(Turelli and Hoffmann, 1991).
These varying results in D. simulans indicate that the
Wolbachia strain and possibly length of association may play a
substantial role in determining activity. The capacity for such different host
responses from within the Drosophila genus does not allow for the
development of broadly generalizable models of wMelPop effects on
behavior. An understanding of the unique effects of wMelPop on
Ae. aegypti will begin in the first instance by characterizing its
tissue distribution and density.
While understanding the mechanism underlying Wolbachia-induced changes in Ae. aegypti is of interest for advancement of the biocontrol strategy, determining whether differences in activity and metabolism substantially change mosquito food-, human host- and mate-seeking behaviours is more important. Each of these activities critically underpins insect fitness in the field and therefore could substantially affect the competitiveness of transinfected Ae. aegypti in a mixed population. In addition, changes to blood feeding or biting rate of Ae. aegypti caused by wMelPop infection may further decrease or increase mosquito vectorial capacity, which this Wolbachia-based strategy aims to reduce.
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Footnotes |
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References |
|---|
|
TOPSummaryINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONReferences |
|---|
Allemand, R., Pompanon, F., Fleury, F., Fouillet, P. and Bouletreau, M. (1994). Behavioral circadian-rhythms measured in real-time by automatic image-analysis-applications in parasitoid insects. Physiol. Entomol. 19,1 -8.[CrossRef]
Ballard, J. W. and Melvin, R. G. (2007). Tetracycline treatment influences mitochondrial metabolism and mtDNA density two generations after treatment in Drosophila. Insect Mol. Biol. 16,799 -802.[Medline]
Bartholomew, G. A., Lighton, J. R. B. and Louw, G. N. (1985). Energetics of locomotion and patterns of respiration in tenebrionid beetles from the namib desert. J. Comp. Physiol. B 155,155 -162.[CrossRef]
Bonatz, A. E., Steiner, H. and Huston, J. P. (1987). Video image-analysis of behavior by microcomputer: categorization of turning and locomotion after 6-ohda injection into the substantia-nigra. J. Neurosci. Methods 22, 13-26.[CrossRef][Medline]
Brownstein, J. S., Hett, E. and O'Neill, S. L. (2003). The potential of virulent Wolbachia to modulate disease transmission by insects. J. Invertebr. Pathol. 84, 24-29.[CrossRef][Medline]
Delthier, V. G. (1976). The Hungry Fly. Cambrige, MA: Harvard University Press.
Dobson, S. L., Bourtzis, K., Braig, H. R., Jones, B. F., Zhou, W., Rousset, F. and O'Neill, S. L. (1999). Wolbachia infections are distributed throughout insect somatic and germ line tissues. Insect Biochem. Mol. Biol. 29,153 -160.[CrossRef][Medline]
Fleury, F., Vavre, F., Ris, N., Fouillet, P. and Bouletreau, M. (2000). Physiological cost induced by the maternally-transmitted endosymbiont Wolbachia in the Drosophila parasitoid Leptopilina heterotoma.Parasitology 121,493 -500.[CrossRef][Medline]
Fuery, C. J., Withers, P. C., Hobbs, A. A. and Guppy, M. (1998). The role of protein synthesis during metabolic depression in the Australian desert frog Neobatrachus centralis. Comp. Biochem. Physiol. A 119,469 -476.[CrossRef][Medline]
Gerberg, E. J., Barnard, D. R. and Ward, R. A. (1994). Manual for Mosquito Rearing and Experimental Techniques. Lake Charles, LA: American Mosquito Control Association.
Grobbelaar, J. H., Morrison, G. J., Baart, E. E. and Moran, V. C. (1967). A versatile, highly sensitive activity recorder for insects. J. Insect Physiol. 13,1843 -1848.[CrossRef]
Hulbert, A. J., Clancy, D. J., Mair, W., Braeckman, B. P., Gems, D. and Partridge, L. (2004). Metabolic rate is not reduced by dietary-restriction or by lowered insulin/IGF-1 signalling and is not correlated with individual lifespan in Drosophila melanogaster.Exp. Gerontol. 39,1137 -1143.[CrossRef][Medline]
Ijichi, N., Kondo, N., Matsumoto, R., Shimada, M., Ishikawa, H.
and Fukatsu, T. (2002). Internal spatiotemporal population
dynamics of infection with three Wolbachia strains in the adzuki bean
beetle, Callosobruchus chinensis (Coleoptera: Bruchidae).
Appl. Environ. Microbiol.
68,4074
-4080.
Kawada, H. and Takagi, M. (2004). Photoelectric sensing device for recording mosquito host-seeking behavior in the laboratory. J. Med. Entomol. 41,873 -881.[Medline]
Lighton, J. R. B. (1991). Measurements on insects. In Concise Encyclopedia on Biological and Biomedical Measurment Systems (ed. P. A. Payne), pp.201 -208. Oxford: Pergamon Press.
Lighton, J. R. B. and Duncan, F. D. (2002). Energy cost of locomotion: validation of laboratory data by in situ respirometry. Ecology 83,3517 -3522.
Liseichikov, Y. N. and Zakharevskii, A. S. (1978). Electronic device for determining motor-activity. Bull. Exp. Biol. Med. 85,696 -697.[CrossRef]
Mankin, R. W. (1994). Acoustical detection of Aedes-taeniorhynchus swarms and emergence exoduses in remote salt marshes. J. Am. Mosq. Control Assoc. 10,302 -308.[Medline]
McGraw, E. A., Merritt, D. J., Droller, J. N. and O'Neill, S.
L. (2002). Wolbachia density and virulence
attenuation after transfer into a novel host. Proc. Natl. Acad.
Sci. USA 99,2918
-2923.
McMeniman, C. J., Lane, A. M., Fong, A. W. C., Voronin, D. A.,
Iturbe-Ormaetxe, I., Yamada, R., McGraw, E. A. and O'Neill, S. L.
(2008). Host adaptation of a Wolbachia strain after
long-term serial passage in mosquito lines. Appl. Environ.
Microbiol. 74,6963
-6969.
McMeniman, C. J., Lane, R. V., Cass, B. N., Fong, A. W. C.,
Sidhu, M., Wang, Y. and O'Neill, S. L. (2009). Stable
introduction of a life-shortening Wolbachia strain into the mosquito
Aedes aegypti. Science
323,141
-144.
Min, K. T. and Benzer, S. (1997).
Wolbachia, normally a symbiont of Drosophila, can be
virulent, causing degeneration and early death. Proc. Natl. Acad.
Sci. USA 94,10792
-10796.
O'Neill, S. L., Hoffmann, A. A. and Werren, J. H. (1997). Influential Passengers: Inherited Microorganisms and Arthropod Reproduction. Oxford: Oxford University Press.
Peng, Y., Nielsen, J. E., Cunningham, J. P. and McGraw, E.
A. (2008). Wolbachia infection alters olfactory-cued
locomotion in Drosophila spp. Appl. Environ.
Microbiol. 74,3943
-3948.
Reynolds, D. R. and Riley, J. R. (2002). Remote-sensing, telemetric and computer-based technologies for investigating insect movement: a survey of existing and potential techniques. Comp. Electron. Agric. 35,271 -307.[CrossRef]
Reynolds, K. T., Thomson, L. J. and Hoffmann, A. A.
(2003). The effects of host age, host nuclear background and
temperature on phenotypic effects of the virulent Wolbachia strain popcorn in
Drosophila melanogaster. Genetics
164,1027
-1034.
Rowley, W. A., Jones, M. D. R., Jacobson, D. W. and Clarke, J. L. (1987). A microcomputer-monitored mosquito flight activity system. Ann. Entomol. Soc. Am. 80,534 -538.
Sbalzarini, I. F. and Koumoutsakos, P. (2005). Feature point tracking and trajectory analysis for video imaging in cell biology. J. Struct. Biol. 151,182 -195.[CrossRef][Medline]
Shirasu-Hiza, M. M. and Schneider, D. S. (2007). Confronting physiology: how do infected flies die? Cell Microbiol. 9,2775 -2783.[CrossRef][Medline]
Shirasu-Hiza, M. M., Dionne, M. S., Pham, L. N., Ayres, J. S. and Schneider, D. S. (2007). Interactions between circadian rhythm and immunity in Drosophila melanogaster. Curr. Biol. 17,R354 .
Turelli, M. (1994). Evolution of incompatibility-inducing microbes and their hosts. Evolution 48,1500 -1513.[CrossRef]
Turelli, M. and Hoffmann, A. A. (1991). Rapid spread of an inherited incompatibility factor in California Drosophila.Nature 353,440 -442.[CrossRef][Medline]
Van Voorhies, W. A., Khazaeli, A. A. and Curtsinger, J. W.
(2003). Selected contribution: long-lived Drosophila
melanogaster lines exhibit normal metabolic rates. J. Appl.
Physiol. 95,2605
-2613.
Van Voorhies, W. A., Khazaeli, A. A. and Curtsinger, J. W.
(2004). Testing the "rate of living" model: further
evidence that longevity and metabolic rate are not inversely correlated in
Drosophila melanogaster. J. Appl. Physiol.
97,1915
-1922.
Weeks, A. R., Turelli, M., Harcombe, W. R., Reynolds, K. T. and Hoffmann, A. A. (2007). From parasite to mutualist: rapid evolution of Wolbachia in natural populations of Drosophila.PLoS Biol. 5,e114 .[CrossRef][Medline]
West, G. B., Woodruff, W. H. and Brown, J. H.
(2002). Allometric scaling of metabolic rate from molecules and
mitochondria to cells and mammals. Proc. Natl. Acad. Sci.
USA 99,2473
-2478.
Williams, C. R. and Kokkinn, M. J. (2005). Daily patterns of locomotor and sugar-feeding activity of the mosquito Culex annulirostris from geographically isolated populations. Physiol. Entomol. 30,309 -316.
Wu, M., Sun, L. V., Vamathevan, J., Riegler, M., Deboy, R., Brownlie, J. C., McGraw, E. A., Martin, W., Esser, C., Ahmadinejad, N. et al. (2004). Phylogenomics of the reproductive parasite Wolbachia pipientis wMel: a streamlined genome overrun by mobile genetic elements. Plos Biol. 2, 327-341.[CrossRef]
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  K. Knight WOLBACHIA PARASITE COULD LIMIT DENGUE FEVER J. Exp. Biol., May 15, 2009; 212(10): i - ii. [Full Text] [PDF]
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