Essay on Lecture 30

Submitted By pghani
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18/10/2013

Eurosta solidaginis:
While not getting frozen…

BIOL 3601 Guest Lecture
Qian Long
Oct 23, 2013 qlong4@uwo.ca Life cycle of goldenrod gall fly Eurosta solidaginis
Females lay eggs on stem of goldenrod

eggs

larvae
Larvae feed and grow in the gall

adults

pupae spring summer
Winter

fall

pre-pupae

pre-pupae

Develop freeze tolerance

Slide by Hiroko Udaka

Insect cold tolerance strategies
1. Chill-susceptibility:
Insects die of cold without freezing
Drosophila melanogaster

2. Freeze avoidance:
Insects cannot survive internal ice formation

Agrilus planipennis

3. Freeze tolerance:
Insects can survive the freezing of their body water
Eurosta. solidaginis
SCP = -8°C
LLT = -40°C

Slide by Hiroko Udaka

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Temperature (ºC)

1

2

alive

1) Chill-susceptible:
Insects die of cold before freezing (SCP< LLT)

3

alive

Body temperature alive

Insect cold tolerance strategies

2) Freeze avoidance:
Insects cannot survive internal ice formation
(SCP=LLT)
3) Freeze tolerance:
Insects can survive the freezing of their body water
(SCP>LLT)

Supercooling
Point (SCP)

E. solidaginis
SCP = -8°C
LLT = -40°C

Time
Slide by Hiroko Udaka
Denlinger & Lee (2010) Low Temperature Biology of Insects

Temperature

Repeated freezing-thawing decreases fitness

spring summer Winter

fall

Seasonal adjustments
• Accumulation of cryoprotectants • Accumulation of TG
• Increase membrane fluidity Freeze tolerant
Slide by Hiroko Udaka

My introduction to E. solidaginis

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My introduction to E. solidaginis
OUR LAB

Glenn Tattersall, PhD (Cambridge)
Blog: Ramphastos Ramblings

Congress of the humanities and social sciences 2014

Hypoxia in plant tissue
• Large size
• Elevated metabolism during growth • Restricted oxygen availability e.g. aquatic or flooding
• Lack specialized circulation system, relies on diffusion
• Exceptions, as always
(aerenchyma)
Aerenchyma in Maize root (Evans, 2004)

Galls ‐ special plant structure
• Plant tissue growth induced by parasite/pathogen
• Gallmaker lives inside for food and protection
• Considered an “extended phenotype”, through which selection acts on the gallmaker • Is condition within the gall a selection force or selectable?

Roger Griffith
(Rosser1954),
Wikipedia
Commons

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Linking galls with hypoxia
• Implications of extra tissue growth:
– Larger size = longer diffusion
– More tissue consumes more oxygen
– High metabolism during growth

• Context: possibility of adaptation against gall hypoxia?
• Is the gall a hypoxic habitat? If so, will the oxygen level affects the gallmaker’s physiology?
– Find evidence for hypoxia
– Compare oxygen level inside gall to the gallmaker’s tolerance to hypoxia Objectives and experiments
• Assess the larva’s tolerance to hypoxia
– Baseline for meaningful comparison

• Model oxygen exchange in the gall
– Factors that should be influential

• Directly measure oxygen level in wild galls
– Actual situation

Tolerance methods
• Larvae exposed to decreasing oxygen levels
• Estimate oxygen level when metabolism and activity falls (critical oxygen level, PC)

CO2 production (ppm)

– Metabolism measured by CO2 production
– Activity monitored by optical sensor
100
80
60
40
20
0
0

5

10
15
20
Oxygen level (kPa)

25

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Tolerance results and discussion
• Constant larval metabolism could not be sustained at
9.5 kPa on average, but activity was sustained until
3.6 kPa (Atmospheric 21 kPa)
• Not lowest among insects, some of which inhabit severely hypoxic environments (even 1 kPa)

Wikipedia

Wikipedia

Gall structure
Skin
Mature cortex
“Fresh” cortex, parenchyma and nutritive layers

Mature cortex

Larval chamber

Interior “fresh” tissue Right: younger gall,
cortex…