The document discusses quantifying changes in hemolymph glucose concentration in crayfish in response to different environmental conditions. It provides background on glucose regulation and production of crustacean hyperglycemic hormone in crayfish. The experiment aims to measure changes in crayfish hemolymph glucose levels when exposed to variations in temperature, salinity, and stress by taking hemolymph samples before and after applying each treatment and comparing glucose concentrations. Safety is emphasized when handling crayfish and needles.

1. Quantifying the hemolymph glucose
concentration response in crayfish

2. Comparative Biology
Why is it so important?
Comparing features (physiology, behavior, etc.)
across different species experiencing similar situations,
helps us to hypothesize trends in how organisms respond to their
environment!

3. Physiology comparisons
Most invertebrates Most vertebrates
Circulatory system:
similar (blood transports nutrients)
but different (open vs. closed)

4. How do we control our behaviors and
energy use?
Endocrine System Central Nervous System

5. Glucose: it’s how cells get energy
 Cellular respiration
 Aerobic (needs
oxygen)
 Anaerobic (no
oxygen available)
 Glucose is required
for both!
 When our muscles
run out of oxygen,
they switch to
anaerobic (much
less efficient!)
 Waste product: lactic
acid

6. Glucose
regulation Hyperglycemic
(too much glucose)
Hypoglycemic (not enough
glucose)

7. Crayfish produce Crustacean Hyperglycemic Hormone
(CHH) from the sinus glands behind their eyes!
This hormone is similar
to glucagon in humans
–
it tells the crayfish’s
body
to release more CHH
glucose
into the hemolymph!

8. Temperature affects
blood-glucose levels
Endotherms (mammals,
birds) and Ectotherms
(reptiles, fish, arthropods,
crustaceans) both need to
maintain proper blood-glucose
levels at different
temperatures (remember
homeostasis?)

9. Salinity affects blood-glucose levels
Substances
absorbed/ingested
from the
environment (food,
air, water) can
affect your body’s
release of
hormones such as
cortisol (stress
hormone), which
can in turn
stimulate other
hormones,
including insulin
and glucagon,
which can affect
your blood-

10. Stress affects blood-glucose
levels
• Stress (searching for
mates, fighting for
territory, avoiding
predators, etc.) can
elevate blood-glucose
levels
• Fight-or-flight response:
Your body releases
many hormones,
including glucagon,
which provides your
cells with more glucose,
so you have more
energy to deal with a
tough situation!

11. For lab today…
 We want to quantify how different conditions induce changes in
crayfish hemolymph glucose concentration.
 Obtain crayfish, take hemolymph sample, apply treatment, take
hemolymph sample again
 Compare before-treatment to after-treatment: is there a change
in glucose concentration?
PLEASE BE CAREFUL WITH YOUR SYRINGES AND NEEDLES,
as well as the crayfish claws
If you have ANY QUESTIONS, please ASK your TA

12. Insert needle under the back of the carapace (1)
Insert
needle at
this angle