Xenacoelomorpha

Question 1

clearly bilaterian for 3 reasons

Answer 1

bilateral symmetry
cephalization
mesodermally derived muscles

Question 2

features:

Answer 2

small d-v flat marine worms.
lack complete gut
lack circulatory & excretory systems

Question 3

3 taxa in xeno

Answer 3

acoela
nemertodermatida
xenoturbellida

Question 4

main taxon: Acoela

Answer 4

400 free-living worms. symbiotic. small. move with cilia

Question 5

acoela - name from?

Answer 5

lack of gut cavity

Question 6

feeding of acoels

Answer 6

extrude gut mass, surround food & pull mass back in.
- immobilizes with mucus.
- food items in vacuole are digested and absorbed.
ventral mouth. undigestible parts ejested

Question 7

nervous system of acoels

Answer 7

cephalization: circular nerves. lacks cross-connectivity

Question 8

sensory feature in acoels

Answer 8

statocyst - fluid filled sensory structure lined with sensory cilia. location of statolith (granule) tells animal how its oriented according to gravity

Question 9

acoel muscle

Answer 9

mesodermally derived
- all the shapes of muscles.
d-v flat body, but shape is changed with muscles.
locomotion not with muscles, with cilia.

Question 10

reproduction of acoels

Answer 10

hermaphroditic.
- males have penis, sperm transfer thru intromission/traumatic insemination.
- internal fertilization, briefly brooded. direct development, reproduce asexually as well

Question 11

taxon xenoturbella of xenocoelomorpha

• similar to acoels
• diff than acoels

Answer 11

Like: statocyst, mesodermally derived muscle, lack complete gut, locomotion by cilia

different: larger, nerves concentrated along circular and longitudinal furrows, small sac-like gut

Question 12

xenoturbellida

repro

Answer 12

hermaphrodites, lack penis

- external fertilization, broadcast spawn. direct development