Crayfish also known as Procambarus clariia are classified as a decapod crustaceans
related to lobsters, crabs, and shrimp. They breathe through the gills as they are aquatic
animals but they can survive for short time outside the water. They have a hard, calcified
exoskeleton that must be shed as they grow. In front of the first abdominal segment
locates crayfish heart in the dorsal portion of cephalothorax.
Crayfish are poikilothermic as their internal temperature is proportional and similar to its
surroundings. Thus, poikilothermic animal metabolic rate and their other physiological
processes associate to its environmental temperature. Crayfish have an open circulatory
system and neurogenic hearts due to which …show more content…
The temperature of water was determined by a thermometer. 1 cm
stripped ends of the wires was hooked into the input posts on the back of the
impendence converter. Lab tutor module was started after.
B. Baseline heart rate
The top of the container was covered with foil and the animal was allowed to sit
quietly for 10 min. The trace was examined by pressing start. After that the baseline
or the controlled heart rate was record for 5 to 10 minutes. After clicking stop the
heart rate was marked as the start and end of the baseline heart rate was traced.
C. Stressed Heart Rate
The container was uncovered and the trace was started. After that the trace was
examined and heart rate was recorded for 5 to 10 minutes. The start and end of the
stressed heart rate trace was marked after it was stopped.
1 mM Serotonin was obtained from the refrigerator. The micropipette with a blue
tip was used to transfer 1 ml of solution to the container. Final concentration of the
holding water was calculated of the neurotransmitter. The animal was allowed to sit
with the foil cover on for 5 minutes so that the neurotransmitter can equilibrate
between the holding water and the animal’s hemolymph. The trace was started …show more content…
The error might have occurred while picking up the highest
stable point in the trace mark. It might also have happened because of the crayfish
being moved constantly while taking the temperature and it was stressed. But
however the result should have been the opposite and the hypothesis should have
been correct. Previous studies on poikilothermic organisms such as Daphnia magna
show a similar relationship in which increased temperature is proportional to
metabolic rate, heart rate, and other physiological processes (Khan, 2008). This may
be due to an increase in enzyme activity which is very influential in metabolic
processes. Since enzyme activity is increased with higher temperatures, more
metabolic processes are able to occur at a faster rate; thus, leading an increase in
heart rate. However our result doesn’t support the hypothesis that increased
temperatures lead to a higher heart rate or vice versa.
The second factor of the experiment was the stress level. For this the crayfish