Animals with a lophophore Flashcards
What phylum have a lophophore?
Bryozoa
Phoronida
Brachiopoda
Entoprocta
How are the Bryozoa, Phoronida and Brachiopoda described?
Tentacular crown (lophophore) present
Coleomate
Mix of protostome and deuterostome characteristics
How are the phylum Entoprocta described?
Tentacular crown present
Acoelomate
Protostomes
What is the lophophore?
Circular or U shaped fold of body wall bearing ciliated tentacles
The cilia drive water currents for filter feeding
What are the characteristic features of animals with a lophophore?
Lophophore
Sessile
Poorly developed head
U-shaped digestive tract
What classes exist within the phylum bryozoa?
Gymnolaemata
Stenoloaemata
Phylactolaemata
What orders exist in the class Gymnolaemata?
Cheilostomata
Ctenostomata
Almost all are marine, includes vast majority of living bryozoan species
What orders exist in the Stenolaemata?
Cyclostomata
Marine, relatively few living but many fossil species
How are the phylum Bryozoa described?
8,000 living species (mostly marine)
Colonial, made up of individual small box-like units called zooids
Different types of zooids may be present (polymorphs)
Feeding polyp termed the lophophore
Metabolites passed between zooids via funicular system
No specialised organs for gas exchange or excretion
What form are the Bryozoans in?
Bryozoan colony form
Colony normally supported by calcified body wall but sometimes by rubbery extracellular matrix or by turgor pressure
What are some colonies in the Bryozoans?
Some colonies are stoloniferous
Stolons composed modified zooids- jointed appearance
Stolons may be erect or run along substrate- normally non-calcified
Feeding zooids often isolated but linked by stolons
What do most species in the Bryozoan’s lack?
Most species lack stolons and zooids in direct contact with each other
What are the common growth forms of the Bryozoans?
Crusts are the most common growth form- on various hard surfaces including algae
Some have nodular or massive coral-like growth forms
Some have bushy seaweed-like growth forms
Some have foliose seaweed-like growth forms
A few colonial forms are mobile
Some solitary species are interstitial and mobile
What are modified in the mobile bryozoans?
Modified bristle-like zooids act as legs allowing the colony to move through and over the surface of the sand
Where do the Bryozoans reside?
Most species coastal but some occur at abyssal depths
Colonise all types of hard surfaces- rock, shell, coral, wood, surface of sand grains
Many specialised epibionts living on algae- adapted for flexibility
Some bore into calcareous substrates
Some exist on surface of sediments
Some are interstitial
What is Lophophore eversion?
Lophophore eversion is controlled by muscular elevation of coleomic pressure
Achieved by different means in the different bryozoan groups
Retraction of introvert is through contraction of the retractor muscles and is much more rapid than protrusion
Sensory cilia on tentacles are exposed during protrusion before lophophore is fully opened
How are the class Stenolaemata described?
Lophophore protrusion not dependent on deformation of body wall
Marine, tubular zooids, calcified cuticle, dominate Palaeozoic bryozoan fossils
Includes the order Cyclostomata and various other orders that have become extinct
What orders exist in the class Gymnolaemata
Order Ctenostomata- exo-skeleton non calcified, no operculum
Order Cheilostomata- Zooids with calcareous walls, operculum usually present, largest group of living marine bryozoans
What sub orders exist within the order Cheilostomata?
Sub-order Malacostega
Zooid with exposed frontal membrane
Sub-order Cribrimorpha
Zooid with frontal membrane covered by vault of calcified spines that may be partially fused
Sub-order Ascophora
Zooid with calcified frontal wall, introvert protrusion by dilation of an internal sac (ascus) connected to exterior by one or more pores
How are the class Gymnolaemata described?
Lophophore protrusion dependent on deformation of body wall
Primarily marine, cylindrical or flattened zooids, polymorphic colonies
Includes the order Ctenostomata and Cheilostomata
How does introvert protrusion work in the order Ctenostomata and sub-order Malacostega?
Ctenostomata- Muscles compress the non calcified flexible body wall and push out introvert
Sub-order Malacostega- Muscles pull in the non-calcified frontal membrane and squeeze out the introvert
How does introvert protrusion work in the sub orders Cribrimopha and Ascophora?
Muscles pull on the ascus which sucks in water through the pores, becomes larger and the introvert is pushed out
How do the Bryozoans feed?
Lophophore is funnel shaped
Cilia draw water current downward
Particles trapped on cilia an transferred to mouth or flicked towards mouth by tentacles
Feeding is selective- particles may be rejected
Small phytoplankton is probably main food
Particles accumulate in mouth then bolus of food passes into gut by peristalsis of muscular pharynx
How does excretion work in the Bryozoa?
No nephridia for excretion- partly by diffusion but may store wastes in body tissues
Every few weeks lophophore and gut degenerate and remains form a dark ball (brown body)
Lophophore and gut are regenerated, brown body may remain in coelom or be expelled via new gut