First published online November 14, 2008
Journal of Experimental Biology 211, 3682-3690 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.019901
Static electric field detection and behavioural avoidance in cockroaches
Philip L. Newland1,*,
Edmund Hunt1,
Suleiman M. Sharkh2,
Noriyuki Hama3,
Masakazu Takahata3 and
Christopher W. Jackson1
1 School of Biological Sciences, Biomedical Science Building, University of
Southampton, Bassett Crescent East, Southampton SO16 7PX, UK
2 School of Engineering Sciences, University of Southampton, Southampton SO17
1BJ, UK
3 Animal Behavior and Intelligence, Division of Biological Sciences, Graduate
School of Science, Hokkaido University, Sapporo 060-0810, Japan
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Fig. 1. The Y-tube choice chamber and the avoidance of static electric fields. (A)
Photograph of the Y-tube apparatus showing the release chamber (RC) connected
to the central chamber (CC). Copper loop electrodes (E), localised the field
to one chamber (C1 or C2). At the end of each tube a capture chamber (CapC)
was attached to hold tested individuals. Aluminium earth bands (EB) were used
to localise the field within the treated chamber. The electrodes (E) were
connected to a Brandenburg Alpha III power source. (B) Vector plot of the
electric field generated by an electrode in one arm of the Y-tube at 1 kV
using Maxwell SV modelling software. (C) The walking path of a control
cockroach tracked using Ethovision software when no electric filed was
present. (D) The walking path of a cockroach when an electric field was
applied to the electrode on the right arm. Note that the cockroach moved
toward the electrode, stopped, and walked back to the left arm to avoid the
electric field. (E) The time taken by cockroaches encountering static electric
fields (SEF) to make a decision within the Y-tube apparatus. The time within
the decision zone was greater when cockroaches were exposed to electric fields
(means ± s.e.m., standard error of the mean), N=40,
P<0.05). (F) The avoidance of static electric fields at different
electrode voltages from 0.5 kV to 4 kV. Cockroaches exhibited no natural bias
for the left or right pathway (N=40, P>0.05) within the
Y-tube apparatus in the absence of electric fields (0 V). Voltage of 0.5 kV
and 0.75 kV did not evoke significant avoidance (N=40,
P>0.05 in both cases). Voltages of 1 kV and above elicited
significant avoidance of the treated pathway (N=40,
P<0.05 in all cases, indicated by the asterisks).
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Fig. 2. The antennae are involved in static electric field detection. (A)
High-speed video images of an animal approaching an untreated electrode within
the Y-tube apparatus. (B) With a 1 kV potential applied to the copper
electrode a bending of the antennae was evident (arrow). (C) Antennal
mechanoreceptor hair plates located on the scape (s), and pedicel (p) of the
dorsal, ventral anterior and posterior locations of a third-instar cockroach
nymph antenna viewed from above. f, flagellum, Hc, head capsule; JM, joint
membrane; P-HP, pedicel hair plate; S-HP, scape hair plate. (D) The
effect of modifying mechanoreceptor input on the preference behaviour of
cockroaches within an untreated Y-tube apparatus. No significant preference
for either the left or right chamber occurred after surgery or restriction of
mechanoreceptor input was performed in the absence of electric fields. HS,
Head–Scape joint; SP, Scape–Pedicel joint. (E) The effect of
modifying mechanoreceptor input on the avoidance of electric fields at 1 kV.
Intact individuals and those with the SP joint fixed exhibited significant
avoidance (N=40, P<0.05, represented by the asterisks).
Avoidance significantly decreased when the antennae were removed, when both
the HS- and SP joint, and when the SP joint alone were restricted in
comparison to intact cockroaches (P<0.05 in all cases). Preventing
exteroceptor stimulation but allowing proprioceptor input did not result in
avoidance (HS and SP exteroceptor) (N=47, P>0.05).
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Fig. 3. Magnetic field deflection of the antennae. Antennal deflection caused by
magnetic field stimulation did not occur in the absence of iron powder applied
to an antenna (A) but did following iron powder application (B) as indicated
by the antennae being attracted towards the coil tip. (C) Mean deflection
(± s.e.m.) of coated adult antennae exposed to magnetic and electric
fields at different potentials. Increasing the electric or magnetic field
strength caused greater antennal deflection. Voltages were selected such that
no significant differences occurred between each field type for a given pair
of potentials (N=5, d.f.=8, P>0.05 in all cases). (D)
Fitted line regression plot of the effect of magnetic fields on antennal
deflection at varying coil potentials (b=0.84, t=2.55,
P<0.05). Dotted lines represent 95% confidence limits.
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Fig. 4. Antennal movement and associated ventral nerve cord (VNC) activity before
and after stimulus onset in individuals with (A) uncoated and (B) coated
antennae. (A) A representative recording showing that the application of a
magnetic field (25 V) to an uncoated antenna caused no change in antennal
deflection in control individuals and no change in VNC activity after stimulus
onset. (Ai) Graph showing mean impulse number (± s.e.m.) recorded from
the VNC 320 ms before (control) and 320 ms after stimulation (test) of the
antennae during magnetic field stimulation from five individuals. Magnetic
field stimulation alone caused no change in impulse number. (B) Representative
recording from an individual with a coated antenna, showing antennal
deflection and increased VNC activity after stimulus onset (25 V). (Bi)
Stimulating coated antennae caused a significant increase in impulse number
after stimulus onset (test) compared with before (control) (N=5,
t=3.4, P<0.05).
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Fig. 5. The role of antennal hair plates during antennal deflection. (A) An example
showing that with the head–scape joint fixed there was little antennal
movement and no evoked activity in the ventral nerve cord (VNC). (B) Magnetic
field stimulation (25 V) did not produce a significant deflection of the
antennae with the head–scape joint fixed (test N=4,
t=–1.9, P>0.05). (C) VNC activity did not
significantly change when antennae were deflected using magnetic fields with
the head–scape joint fixed (test N=5, t=0.5,
P>0.05).
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Fig. 6. Avoidance of magnetic fields (MF) by animals with iron-particle-coated
antennae. (A) Photograph of the electromagnet Y-tube apparatus. The distal end
of an electromagnet (Coil) was positioned at the entrance to both the anterior
pathways. C1 and C2, chambers; CC, central chamber. (B) The time taken by
cockroaches confronted by MF to make a decision within the Y-tube apparatus.
The time in the decision zone was greater when cockroaches were exposed to MF
(N=40, P<0.05). The decision time did not differ between
individuals exposed and not exposed to MF without iron powder (N=40,
P>0.05). MF did, however, have an effect on cockroach decision
time when antennae were coated with iron particles (N=44,
P<0.05).
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Fig. 7. Summary of effects of electric fields on the cockroach. (A) Before
encountering a positively charged electrode the electrical charges on a
cockroach are randomly distributed (+ and –, positive and negative
charges, respectively). (B) As a cockroach approaches a positively charged
electrode the electric field induces an uneven charge distribution on the
cockroach with negative charges being attracted to the antennae, which, in
turn, causes passive deflection of the antennae towards the electrode as
opposite charges are attracted. (C) The passive deflection of the antennae is
detected by sensory receptors at their base (the head–scape hair plate)
that generates a withdrawal of the antennae away from the electrode leading to
a pronounced bending of the antennae.
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© The Company of Biologists Ltd 2008
