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

Why do females prefer extreme displays?

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

TEMPERATURE PROTECTION EXPERIMENT

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

Summary

Intertidal habitats present physical challenges to development on several time scales

development rate risk of heat stresstemperatures lead to

mass dislodgment: spring tides = neap tides

embryo mass production after hot days