15.Mollusca

Question 1

Mollusca

Ancylidae

Answer 1

Structure
• Shells flattened limpet-like
• Base of shell wide, round or oval
• Resembles a sand dune when viewed from the side

Behaviour
• Slow gliding movement

Habitat
• On rocks or any solid submerged substrate
• All streams country-wide

Question 2

Mollusca

Lymnaeidae

Answer 2

Structure
• Shell opening on the right
• Shell opening large, wide
• Triangular tentacles

Behaviour
• Slow gliding movement

Habitat
• Gravel beds, or on aquatic vegetation

Question 3

Mollusca

Physidae

Answer 3

Structure
• Shell opening to the left
• Shell smooth, glossy
• Slender tentacles

Behaviour
• Slow gliding movement

Habitat
• Gravel beds, or on aquatic vegetation

Question 4

Mollusca

Planorbidae

Answer 4

Structure
• Flat shell, tightly coiled
• Host for the bilharzia parasite

Behaviour
• Slow moving on the foot
• Shell in vertical position when animal moves around

Habitat
• Gravel beds or aquatic vegetation
• Flowing streams

Question 5

Mollusca

Thiaridae

Answer 5

Structure
• Strong, thick shell
• Well-developed spiral
• Tubercles more pronounced in some individuals

Behaviour
• Slow moving on the foot

Habitat
• Gravel beds in flowing streams
• Silty substrate in pools

Question 6

Mollusca

Corbiculidae

Answer 6

Structure
• Strong hard shell
• Prominent growth lines
• Strong hinge

Behaviour
• Appears to be inactive

Habitat
• Sand or gravel beds
• Flowing streams

Question 7

Mollusca

Sphaeriidae

Answer 7

Structure
• Small, fragile shells
• Smooth without growth rings

Behaviour
• Inactive

Habitat
• Sand or gravel beds

Question 8

Mollusca

Unionidae

Answer 8

Structure
• Large elongate shells
• Prominent growth rings
• Erosion of the outer layer visible

Behaviour
• Inactive
• Two halves open slightly when filtering water

Habitat
• Deep muddy substrate