P1247676900TLyoX

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Sublethal insecticide exposure influences
behaviors of web-building spiders
William J. Tietjen1 and Alan B. Cady2 1Department
of Biology, Bellarmine College, Louisville,
KY 2Dept. of Zoology, Miami University-Middletown,
Middletown, Ohio
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Topics

• Pesticide effects on spider behaviors
• Malathion effects on spiders - laboratory
• Malathion effects on spiders - field
• Mechanisms and implications

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Pesticides and Spiders

• Chemical applications are part of IPM scheme

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Integrated Pest Management (IPM)

• Integration of farming practices, chemical
  applications, and biological control techniques

Agricultural Practices
Biological Controls
Chemical Controls
C R O P
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Pesticides and Spiders

• Chemical applications are part of IPM scheme
• Spiders the dominant Generalist Predatory
  Arthropods subject to chemical applications
• Most doses are sublethal to spiders
• Surveys show spiders survive and are present in
  fields
• Subject to repeated doses
• Contact chemical residues on vegetation
• Consume contaminated prey
• Webs serve as collectors chronic contact
  consumption

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Laboratory Studies of MalathionSexual,
Locomotor, Predatory behaviors

• Changes in sexual behavior of Rabidosa rabida
• Proper male courtship but cannot switch to
  mating
• (Tietjen 2006)
• Amount, duration, and patterns of movement
  changed from exposure to malathion
• More movements, greater distance, circadian
  shifts
• (Tietjen Cady in press)
• Altered predatory abilities after exposure
• Improper tracking and attack of prey by
  Salticus (Tietjen unpub data)

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Effects on Orb-Web Spiders

• Previous studies show spiders survive malathion
  application but are behaviorally crippled
• Orb-weaving spider affected by pyrethroid
• Decreased web size, accuracy, frequency
• (Samu Vollrath 1992)
• Pharmeceuticals affect spider CNS
• Test effects of malathion on orb-weaving spiders
  receive more exposure to chemicals

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Malathion Effects - Orb-Web Spiders Laboratory
Araneus diadematus
Aranues marmoreus
Housing
Dosing

• Spiders kept in Witt Cages
• Fed flies and sprayed with water

• Spiders kept in Petri dish with filter paper
  holding malathion (a.k.a. chlorpyrifos ww)
• - 10 µl of 10-4 or 10-7 (A. diadematus) or
• - 10-5 (A. marmoreus)
• Exposed for 24 hours

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Web measurement Protocols
- Webs were photographed by illuminating from the
side and using a Kodak 700 digital camera.
- An alternate technique used video images
digitized with a frame-grabber. This permitted
consistent, repeated sampling of the web over
long periods (daily across 58 days).
- Spiders served as their own Control by being
measured daily across 10 days prior to dosing.
Web images were enhanced to expose structures.
After
Before
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Web measurement Protocols

• - Web structures were identified and marked
• - A vectorized image was produced.

- A computer program analyzed the image and
extracted raw data
Catch area Regularity index Mesh distances Radii
angles Radii lengths
- Extremely irregular webs were excluded from
analyses.
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Findings from A. diadematus and A.
marmoreus
- Data were analyzed to determine trends related
to dosage and possible recovery.
Araneus diadematus
Dosed spiders built smaller, more irregular
webs.
Same animal same scale
No recovery after 58 days (10-7 dose)
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Findings from A. diadematus and A.
marmoreus
Araneus marmoreus
Dosed spiders were incapable of building orb
webs.
Tangled lines
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Araneus marmoreus results
A smear of silk on the glass cage
- No A. marmoreus recovered from the 10-5 dose of
malathion after 7 weeks.
- Web-building behaviors of Araneus diadmeatus
and A. marmoreus were significantly affected by
doses of malathion ranging from 10-4 ? 10-7
(ww). Araneus diadematus showed a dose response
(10-4 changed more than 10-7). - Dosed A.
diadematus stopped eating.
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Malathion Effects - Orb-Web Spiders Field
Argiope trifasciata
Housing
- Six 5m X 5m X 2.5m screened wooden frames in
0.5 hectare soy field. - 10 marked spiders in
each all built webs.
Dosing
- Broadcast sprayed Interior of enclosure
sprayed with 1 liter of 10 ppm malathion. -
Individually Dosed Spiders held in jar with
filter paper holding 10 ppm malathion for 24
hours. - Web dimensions measured and videotaped
movements monitored until frost-killed.
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Web measurement Protocols
- Spiders released, observed for 30 days, then
dosed. - Webs videotaped in field with 8mm
camcorder to record web structures. - Video
frames digitized and enhanced for analyses
similar to that for A. diadematus and A.
marmoreus.
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Web measurement Protocols
- Web structures measured similarly to lab
protocols. - Computer-assisted data gathering
and analyses.
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Findings from Argiope trifasciata in the field
- Box-and-Whisker plots to visualize relationships
- Mann-Whitney tests to compare mean values
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Findings from Argiope trifasciata in the field
Control
Dosed
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Findings from Argiope trifasciata in the field
Overall differences
Analyses of Web Shape spiders dosed with 10 ppm
malathion showed         - greater outer spiral
distance         - greater radii area         -
greater mesh distance for 0, 90, 180, and 270
degree directions         - less regularity -
Apparently larger dosed webs and no difference in
capture area between treatments is an artifact
related to problems obtaining images in the
field. - Large webs for Control
under-represented silk more difficult to
image Analyses of data Derived from
measurements, dosed spiders showed         -
greater 90 degree radii distance         -
greater 90 degree mesh count         - greater
90 degree center to outside distance- No current
explanation for differences appearing at
90-degree direction
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Other findings from Argiope trifasciata in the
field
- Direct web measurements showed dosed spiders
built smaller webs.




- Sprayed spiders moved more often than other
treatments
B
A
A
C
These results consistent with those from the lab
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S u m m a r y

• Araneus diadematus and A. marmoreus significantly
  altered their web structures after receiving
  sublethal doses of malathion.
• Similar alterations of web structure were seen in
  Argiope trifasciata living in a soybean field.
• - Different protocols necessary for field
  web imaging
• These structural changes (smaller, more irregular
  webs, or no web at all) would significantly
  impact the animals ability to efficiently secure
  prey.
• Acetylcholine esterase activity greatest in leg
  ganglia connective ring systems of ventral
  nerve cord important neural integration regions.
• Inhibition in these areas could impair
  coordination.

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Acknowledgements and references
- USDA Grant 94-37311-1189 to ABC - USDA Grant
94-37311-1186 to WJT - Miami University - Ecology
Research Center of Miami Univ.
Samu, F. F. Vollrath. 1992. Spider orb web as
bioassay for pesticide side effects. Entomologica
Experimentalis et Applicata 62117-124. Tietjen,
W.J. 2006. Pesticides Affect the Mating Behavior
of Rabidosa rabida (Araneae, Lycosidae). Journal
of Arachnology 34(2) 285-288. Tietjen, W.J.
A.B. Cady. Sublethal exposure to a neurotoxic
pesticide affects activity rhythms and patterns
of four spider species. In Press Journal of
Arachnology.