Question

Musculature of the Clam

4.

a) What are the large, prominent muscles ventral to the hinge that attach to the right and left valves? (2 points)

b) What is the function of these muscles? (2 points) Musculature of the Crayfish

5.

a) Pull on the dactyl’s apodeme to simulating muscle contracting against it. What movement is produced? (1 point)

b) The area of the apodeme can be used to estimate the muscle force delivered to the chela. Try to explain why this measurement would be a good indicator of muscle force. (1 point)

Musculature of the Perch

6. Compare ventral flexion of the abdomen in crayfish to lateral body undulation in the perch.

a) Describe one structural and one functional similarity. (3 points)

b) Describe one structural and one functional difference. (3 points)

Musculoskeletal System of the Frog

7. Which of the frog hindlimb muscles you identified are responsible for these movements? If more than one muscle contributes to a particular movement, list all muscles. (4 points)

a) Extension at the knee

b) Extension at the ankle

c) Hindlimb adduction / protraction

d) Flexion at the knee

8.

a) What hindlimb movements are involved in the propulsive phase of jumping? The propulsive phase powers the frog forward. (2 points)

b) What hindlimb movements are involved in the recovery phase of jumping? The recovery phase returns the limbs to a position where they can power the next propulsive phase. (2 points)

9.

a) Name a pair of hindlimb muscles that function antagonistically. (1 point)

b) Name a pair of hindlimb muscles that function synergistically. (1 point)

Answer 1

4. Musculature of the Clam

a) The two valves are pulled together by a pair of adductor muscles, one anterior and one posterior. When contracted these muscles pull the valves together, which causes in stretching the hinge ligament,which is elastic.When the adductor muscles relax the hinge ligament returns to its original shorter length and this pulls the umbos closer together and the ventral margins of the valves move apart.

b) When the adductor muscles relax the hinge ligament returns to its original shorter length and this pulls the umbos closer together and the ventral margins of the valves move apart.   The shell thus opens slightly along the ventral border.   The small gap thus created between the edges of the two valves is the gape. Inside surface of one of the valves, there are two smooth elliptical areas, one anterior and one posterior.   These are the anterior and posterior adductor muscle scars , respectively, and they are the sites of attachment of the adductor muscles.