Animals with a lophophore

Question 1

What phylum have a lophophore?

Answer 1

Bryozoa
Phoronida
Brachiopoda

Entoprocta

Question 2

How are the Bryozoa, Phoronida and Brachiopoda described?

Answer 2

Tentacular crown (lophophore) present
Coleomate
Mix of protostome and deuterostome characteristics

Question 3

How are the phylum Entoprocta described?

Answer 3

Tentacular crown present
Acoelomate
Protostomes

Question 4

What is the lophophore?

Answer 4

Circular or U shaped fold of body wall bearing ciliated tentacles
The cilia drive water currents for filter feeding

Question 5

What are the characteristic features of animals with a lophophore?

Answer 5

Lophophore
Sessile
Poorly developed head
U-shaped digestive tract

Question 6

What classes exist within the phylum bryozoa?

Answer 6

Gymnolaemata
Stenoloaemata
Phylactolaemata

Question 7

What orders exist in the class Gymnolaemata?

Answer 7

Cheilostomata
Ctenostomata
Almost all are marine, includes vast majority of living bryozoan species

Question 8

What orders exist in the Stenolaemata?

Answer 8

Cyclostomata
Marine, relatively few living but many fossil species

Question 9

How are the phylum Bryozoa described?

Answer 9

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

Question 10

What form are the Bryozoans in?

Answer 10

Bryozoan colony form
Colony normally supported by calcified body wall but sometimes by rubbery extracellular matrix or by turgor pressure

Question 11

What are some colonies in the Bryozoans?

Answer 11

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

Question 12

What do most species in the Bryozoan’s lack?

Answer 12

Most species lack stolons and zooids in direct contact with each other

Question 13

What are the common growth forms of the Bryozoans?

Answer 13

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

Question 14

What are modified in the mobile bryozoans?

Answer 14

Modified bristle-like zooids act as legs allowing the colony to move through and over the surface of the sand

Question 15

Where do the Bryozoans reside?

Answer 15

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

Question 16

What is Lophophore eversion?

Answer 16

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

Question 17

How are the class Stenolaemata described?

Answer 17

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

Question 18

What orders exist in the class Gymnolaemata

Answer 18

Order Ctenostomata- exo-skeleton non calcified, no operculum

Order Cheilostomata- Zooids with calcareous walls, operculum usually present, largest group of living marine bryozoans

Question 19

What sub orders exist within the order Cheilostomata?

Answer 19

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

Question 20

How are the class Gymnolaemata described?

Answer 20

Lophophore protrusion dependent on deformation of body wall
Primarily marine, cylindrical or flattened zooids, polymorphic colonies
Includes the order Ctenostomata and Cheilostomata

Question 21

How does introvert protrusion work in the order Ctenostomata and sub-order Malacostega?

Answer 21

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

Question 22

How does introvert protrusion work in the sub orders Cribrimopha and Ascophora?

Answer 22

Muscles pull on the ascus which sucks in water through the pores, becomes larger and the introvert is pushed out

Question 23

How do the Bryozoans feed?

Answer 23

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

Question 24

How does excretion work in the Bryozoa?

Answer 24

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

Question 25

What is zooid polymorphism?

Answer 25

Most species have colonies composed of different types of zooid

Question 26

What are the different types of zooid?

Answer 26

Autozooids:

Heterozooids:
- Kenozooids
- Avicularia
- Vibracula
- Ovicell
- Gonozooid

Question 27

What are the functions of the Autozooids and Heterozooids?

Answer 27

Autozooid- typical feeding zooid, makes up bulk of colony
Heterozooid- zooids which are reduced or modified for various functions (kenozooids, avicularia, vibracula, gonozooids, ovicells)

Question 28

What are the functions of the many heterozooids?

Answer 28

Kenozooids- form stolons, attachment disks or rootlike structures, structurally simple

Avicularia- Defensive structure- operculum and associated muscles modified to form powerful jaws, usually smaller than autozooid, internal structure greatly reduced, may be stalked or sessile

Vibracula- Operculum modified to form long moveable bristle (or seta)
Usually function is to sweep away silt or other fouling material

Ovicell- modified to form chamber for brooding eggs

Gonozooid- zooid modified to form to form chamber for brooding eggs/embryos

Question 29

What are the main two structures in the phylum Entoprocta?

Answer 29

Calyx- feeding structures and internal organs

Stalk- provides attachment to substrate, often partitioned forming apparent segments, contains muscles allowing for movement, some can detach base of stalk, crawl and reattach

Question 30

How are the phylum Entoprocta described?

Answer 30

150 species (mostly marine)
Colonial (2 families) or solitary (1 family)
Stalked, tentacular zooids (<5mm long)
Mostly sessile, attached to hard substrates or commensal on other animals
Superficially similar to bryozoans- but: spiral rather than radial cleavage, no coelom, anus opens within tentacle ring, no exoskeleton

Question 31

What are the growth forms of the Entroprocta?

Answer 31

Solitary- single stalk
Colonial- several stalks from common attachment disc
Colonial- multiple stalks from stolonal system that may be recumbent or erect

Question 32

How are the phylum Phoronida described?

Answer 32

14 species (all marine)
Solitary
Worm like animal generally <20cm long living in chitinous tube
Tube buried in sand or attached to hard substrate
Some bore into calcareous substrate
Well developed blood vascular system with corpuscles containing hemoglobin as respiratory pigment

Question 33

How are the phylum Phoronida structured?

Answer 33

Conspicuous lophophore
Trunk has no appendages and limited differentiation
Bulbous posterior ampulla
Gut U shaped, anus opens outside of lophophore
Coelom partitioned longitudinally by mesentries
Can rapidly retract into tube but movement is otherwise slow
Gas exchange at lophophore, efficient blood system
Has excretory system (metanephridia)

Question 34

How are the phylum Brachiopoda described?

Answer 34

325 species (all marine)- but 12,000 fossil species, most extinct at end of Permian
Superficial resemblance to bivalve molluscs
Occur from intertidal to abyssal, mostly found in cold water
Most live attached to solid substrates but some are burrowers
Pedicle protruding from valves is characteristic feature

Question 35

What classes exist within the phylum Brachiopoda?

Answer 35

Class Inarticulata- Valves held together only by muscles, opening achieved by contracting body to back of shell

Class Articulata- Posterior margin of valves have hinge teeth to form an articulating joint, opening and closing by direct muscular action

Question 36

How is the pedicle arranged in the classes Inarticulata and Articulata?

Answer 36

Inarticulata- emerge directly between valves, long and muscular
Articulata- emerge from notch or hole in the ventral valve, may be flexible and muscular or short and lacking muscles, if non muscular then muscles within valves still allow for movement on pedicle

Question 37

What are the different life modes in the phylum brachiopoda?

Answer 37

Attached to hard substrate by pedicle
Cemented directly to hard substrate- pedicle absent
Free living on sediment surfaces- fossil species with spines and wings, some living species
Burrowers in sediments

Question 38

How is the anatomy of the brachiopoda described?

Answer 38

Internal organs posterior in shell- lophophore occupies anterior part
Inarticulates have anus opening between the valves, articulates have a blind gut
No specialised gas exchange organs- occurs on lophophore
Excretory system with metanephridia
Blood vascular system with dorsal heart

Question 39

How is the lophophore structured?

Answer 39

Primitively U-shaped but variously looped, folded or spiralled for increase of surface area
Ciliated cells have only one cilium (like phoronids)- cilia drive water current, trapped particles transported along branchial groove to mouth
Lophophore supported by cartiliaginous structure and often by projections of inner surface of shell valve