Protection from thermal stress in embryo masses of Melanochlamys diomedea
Protection of embryos from heat stress during early developmental stages
Variation in habitat temperatures over different spatial and temporal scales
Patterns of protein expression and their variation as a function of larval temperature exposure
Construction, placement, and persistence of embryo masses under natural conditions
Protection from thermal stress in embryo masses of Melanochlamys diomedea
Natural history of embryo masses
Is development protected from heat stress?
Patterns of variation in habitat temperature
Heat-inducible expression of novel proteins
Female mate choice
• Males in diverse taxa often have extreme, showy secondary sexual characteristics
• Extreme displays may have evolved to attract females
• However, biologists are unsure of why females prefer showy males
Temperature protection experiment: methods
1. A single embryo mass was divided into eight parts.
2. Four parts were exposed to a 29C heat shock, and four to 12C control temperatures. Each set of four was then treated as follows:
• One was immediately radiolabeled and processed for heat shock expression
• One was exposed to a 35C heat stress for 0.5 h, and one for 1.5 h, and then both were processed
• One was exposed to a 35 C heat stress and then transferred to seawater to monitor embryos for normal development
Changes in growth by age and sex
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5
Dosage
Gro
wth
Adult maleAdult femaleJuv maleJuv female
Males respond to increased dosagemore than females
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4 5Dosage (mg)
Gro
wth
(cm
)
Male (adult)Male (juv)Female (adult)Female (juv)
Temperature in tide pools
15 20 25 30 35
Temperature (oC)
Tem
per
atu
re o
n f
ollo
win
g d
ay (
o C)
R2 = 0.37
10
15
20
25
30
35
10
Maximum temperature is correlated between days
10
15
20
25
30
35
10 15 20 25 30 35
Maximum temperature (°C)
Maximum temperature
on next day (°C)
R2 = 0.37
Table 3. Results of the selection analysis. Standardized directional selection differentials (s') and gradients (') for mean ovum and jelly volume, and standardized quadratic
selection gradients (') for variance of characters and covariance between characters
____________________________________________________________________
Trial s' (means) ' (means) ' (variances,covariance)______________
Ovum Jelly Ovum Jelly Ovum Jelly Ovum-Jelly____ _____ _____ _____ _____ _____ ______ _________
1 -0.146* -0.203** -0.117 -0.185* -0.298* 0.115 -0.036
2 -0.518** -0.378** -0.451** -0.263** 0.012 0.239* 0.094
3 -0.293* -0.253* -0.257* -0.209* 0.386* 0.157 -0.165*
4 -0.192* -0.249** -0.170* -0.233** -0.295* 0.080 0.017
5 -0.156* -0.189* -0.110 -0.157* 0.397* 0.056 -0.261*
____________________________________________________________________
Mean -0.261 -0.254 -0.221 -0.209 0.040 0.130 -0.070
SE 0.069 0.033 0.063 0.018 0.154 0.032 0.064
____________________________________________________________________
* P < 0.05, ** P < 0.01
Selection gradients for ova and jelly coats
Trial Ovum Jelly
1 -0.117 -0.185*
2 -0.451** -0.263**
3 -0.257* -0.209*
4 -0.170* -0.233**
5 -0.110 -0.157*
Mean (SE) -0.221 (0.063) -0.209 (0.018)
* P < 0.05, ** P < 0.01
Summary
• Intertidal habitats present physical challenges to development that can vary on several temporal and spatial scales
• Increased temperatures during a spring-tide series can speed development, but
• high temperatures also increase risks of high temperature stress especially for early stages that cannot synthesize hsps
• Although many masses may be dislodged before they mature, increased water exchange during the spring-tide series does not appear to result in greater risk of dislodgment
• Adults deposit masses with similar frequency during spring- and neap-tide series
• less likely to deposit masses following hot days
Summary
Intertidal habitats present physical challenges to development on several temporal scales
Increased temperatures speed development but also increase risk of stress
Increased water exchange during the spring-tide series does not increase dislodgment
Adults are less likely to deposit masses following hot days
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