What are the 2 lifestyles of bryozoans?
- Colonial
2. Sessile
What type of feeding do they do?
They suspension feed.
What feeding structure do they use (and what is it)?
A lophophore, which is a funnel of ciliated tentacles.
The crown of ciliated tentacles draws water down into the funnel of tentacles to create a feeding current.
What is their exoskeleton called?
What are the 2 things it might be made of?
Called the zooecium
Often calcified, but sometimes tough and proteinaceous.
What type of digestive tract do they have?
U-shaped
Are they true eucoelomates?
If so, what is/are the coelomic compartments called?
Yes.
- Lophophoral coelom in their hollow tentacles
- Perivisceral coelom
What implications does their small size have on their morphology?
No specialized organs for:
- Gas exchange
- excretion/osmoregulation
- Internal fluid circulation
How does internal fluid circulation work?
Mesothelium lining coelomic compartments is ciliated, beating of cilia keeps coelomic fluid in circulation to distribute nutrients, gases.
How does excretion/osmoregulation occur?
Diffusion across the body wall. No protonephridia or metanephridia.
Name and describe the diversity of colony forms.
- Stoloniferous
- stolon branches out over rocks, cluster reaches up every now and then - Encrusting
- zooids lie flat against rock, lophophore arises from VENTRAL surface (not apical) - Erect
- branched fronds or flat blades reach up from substrate
How do encrusting colonies grow?
- oldest zooid settles in middle
- bud off periphery
How do branched fronds/flat blades form form (and what type of colony are the in)
- formed from individual zooids with their zooecium
- erect colonies
Describe the only solitary bryozoan’s name and lifestyle/habitat.
Called a monobryozoan
- is solitary
- lives between sand grains
What is colony polymorphism?
The DIVISION OF LABOUR:
- different zooids are specialized for different jobs
- are structurally and functionally distinct
What are the types of zooids and their roles?
Autozooids: feeding
Heterozooids: defense
-prevents settling of organisms on colony
What is the special name for heterozooids? How are they modified?
Avicularium (avicularia)
-have modified operculum that closes shut on intruding larvae/particles
How can motile bryozoan colonies move?
With heterozooids called vibraculum.
-are whip-like features that prevent debris settling AND act as legs
Are bryozoans hermaphroditic or gonochoristic?
Hermaphroditic
-have both male and female reproductive systems
What are the life history stages of encrusting bryozoan colony zones?
Inside->outside
- REGENERATION (from brown body) at center
- REGRESSION (brown bodies)
- Sexually Mature
- Maturing
- Budding (periphery)
What are the defensive strategies of bryozoans?
- Heterozooids
- Colonialism
- Chemical Defenses (toxic/unpalatable chemicals)
- Induced defenses
- Calcification of frontal membrane
What are induced defenses?
- only expressed if animal under threat
- default mode doesn’t have these
- take a while to form (are not instant)
What is an example of a predator and an induced defense?
Predator: Nudibranch
-chemical effluent from them causes growth of pines from 4 corners of zooecium
Describe lophophore retraction/extension with a non-calcified frontal membrane
Retratction:
1. Lophophore RETRACTOR muscles contract
2. Increases coelomic pressure, bulges frontal membrane outwards
Extension:
1. Lophophore PROTRACTOR muscles contract
2. Raises coelomic pressure and pushes lophophore out again
What do they used to extend/retract their lophophore?
A HYDROSTATIC skeleton with muscles
