Mesozoans

Question 1

Mesozoan Classes

Answer 1

Cl. Orthonectida

Cl. Rhombozoa

Question 2

Mesozoan Characteristics

Answer 2

Small
Parasitic
1st called ciliated protists
Multicellular 10-40 cells
2 tissues: ectoderm and mesoderm
May have exhibited lateral gene transference
Ciliated body
Develop intracellularly

Question 3

Orthonectida Characteristics

Answer 3

Parasite of bivalve mollusk so
Small
Gonochoristic (m and f)
Plasmodia larvae
Juveniles relie on host

Question 4

Plasmodia larvae

Answer 4

Orthonectida
Live in host; cannot sexually reproduce
Produce sexually mature adult within that leaves and mates

Question 5

Rhombozoa Characteristics

Answer 5

Parasite of cephalopod nephridia or kidneys
Live off host urine
5 step reproduction

Question 6

Rhombozoa reproduction

Answer 6

1. Primary nematogen (axial cells and axoblast cells)
2. Proliferate nematogens
3. Transform into or create last generation of rhombogens
4. Rhombogen axoblasts differentiate into infusorigens
5. Self-fertilize and release ciliated infusoriform larvae that find new host

Question 7

Primary Nematogen

Answer 7

1st stage in kidney
Vermiform
20-30 ciliated cells surround an axial cell that forms a central shaft

Question 8

Axial cell

Answer 8

Central shaft and reproductive center; contains axoblasts

Question 9

Axoblast cells

Answer 9

Within axial cell

Develops into more asexual reproducing nematogens, which create more axoblasts

Question 10

Rhombogen

Answer 10

Sexual stage of Rhombozoa
Morphologically same as nematogen
Rhombogen axoblasts differentiate into non-ciliated infusorigens that never emerge
- simultaneous hermaphrodites

Question 11

Infusoriform Larvae

Answer 11

Zygotes
Ciliated
Find new host