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
What is zooid polymorphism?
Most species have colonies composed of different types of zooid
What are the different types of zooid?
Autozooids:
Heterozooids:
- Kenozooids
- Avicularia
- Vibracula
- Ovicell
- Gonozooid
What are the functions of the Autozooids and Heterozooids?
Autozooid- typical feeding zooid, makes up bulk of colony
Heterozooid- zooids which are reduced or modified for various functions (kenozooids, avicularia, vibracula, gonozooids, ovicells)
What are the functions of the many heterozooids?
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
What are the main two structures in the phylum Entoprocta?
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
How are the phylum Entoprocta described?
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
What are the growth forms of the Entroprocta?
Solitary- single stalk
Colonial- several stalks from common attachment disc
Colonial- multiple stalks from stolonal system that may be recumbent or erect
How are the phylum Phoronida described?
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
How are the phylum Phoronida structured?
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)
How are the phylum Brachiopoda described?
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
What classes exist within the phylum Brachiopoda?
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
How is the pedicle arranged in the classes Inarticulata and Articulata?
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
What are the different life modes in the phylum brachiopoda?
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
How is the anatomy of the brachiopoda described?
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
How is the lophophore structured?
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
