Micrognathozoa

Question 1

Characteristics (5)

Answer 1

Microscopic, bilaterally symmetrical acoelomates.

Have a complex jaw apparatus (more intricate than those of Rotifera and
Gnathostomulida).

Covered with cilia for locomotion.

Lack a circulatory and respiratory system, relying on diffusion.

Can contract their bodies to change shape.

Question 2

general adult body form

Answer 2

Size: Extremely small (~100–150 µm in length).

Question 3

body wall and support

Answer 3

Body Wall: Soft-bodied and covered in cilia for movement.

Support: Hydrostatic support due to internal fluid.

Question 4

locomotion (2) and body cavity

Answer 4

Locomotion:
-Moves using cilia along its ventral side.
- Can also flex and contract its body to maneuver.
-
Body Cavities: Lacks a true coelom (acoelomate).

Question 5

feeding/digestion (2) and circulation

Answer 5

Nutrition (Feeding/Digestion):
-Feeds on bacteria and detritus using a complex, multi-part jaw
apparatus.
-The pharynx helps transport food to the gut for digestion.

Circulation: No circulatory system; diffusion facilitates nutrient and gas
exchange.

Question 6

excretion and respiration

Answer 6

Excretion (Osmoregulation): Uses protonephridia (flame cells) for waste
removal and osmoregulation.
-
Gas Exchange (Respiration): Oxygen exchange occurs through diffusion across
the body surface.

Question 7

nervous system (2)

Answer 7

Has a simple nerve net and brain-like ganglia.
●
Possesses sensory cilia and possibly mechanoreceptors.

Question 8

reproduction and development

Answer 8

Only females have been discovered; reproduction may involve
parthenogenesis (asexual reproduction).
●
Eggs develop into miniature versions of adults (direct development, no
larval stage).

Question 9

habitat (2)

Answer 9

Found in freshwater environments, specifically cold-water springs in Greenland.

Likely adapted to interstitial spaces (living between sand grains).

Question 10

when were they discovered?

Answer 10

Discovered in 2000, making it one of the most recently described phyla.

Question 11

Why are the called that?

Answer 11

Named Micrognathozoa due to its tiny but highly complex jaw system.

Question 12

What are they closely related to?

Answer 12

Shows similarities to both rotifers and gnathostomulids, suggesting an
evolutionary link.

Question 13

How many species?

Answer 13

1 is known