1. Polyzoa and Kryptrochozoa
CHAPTER 15
Polyzoa and Kryptrochozoa
Powerpoints revised by Franklyn Tan Te
Copyright © McGraw-Hill Education.  All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.

2. Ectoprocts (Bugula neritina) and other animals fouling a boat bottom.

3. Evolutionary Experiments
Greatest evolutionary “bang” the world has known occurred 570 million years ago called the Cambrian Explosion
Fossil evidence indicate that all major phyla and most small phyla became established.
Many phyla existed in the Paleozoic than today but have since disappeared due to several major extinction events that have led evolution to go through many “experimental models”.

4. Lophophores
Phylogenetic evidence indicates that lophophores evolved more than once.
Lophophores have a crown of ciliated tentacles that are used in food capture and respiration.
Cavity inside the lophophore is part of the coelom and filled with coelomic fluid.
Thin ciliated walls act as respiratory surface for gas exchange.
Lophophores normally extended but can be withdrawn for protection.

5. Lophophores
Three major phyla were previously lumped under lophophores: Phoronida, Ectoprocta, Brachiopoda
Lophophores and animals with trochophore larvae features are merged to form a new group called Lophotrochozoans
Ectoprocta is now placed in a clade called Polyzoa with Cycliophora and Entoprocta where all three taxa share ciliated tentacles.
Brachipoda and Phoronida are placed in the clade Brachiozoa.

6. Figure 15.1 Proposed relationships among polyzoans and kryptrochozoans.

7. Phylum Cycliophora
Phylogenetic studies using multiple genes have supported the clade Polyzoa that unites the cycliophorans, entoprocts and ectoprocts.
Members of the three groups have fascinating body plans and life cycles.
Cycliophorans live exclusively on mouthparts of marine decapod crustaceans in northern hemisphere
Attach to bristles with an adhesive disc on the end of an acellular stalk

8. Figure 15.2 Symbion pandora, a cycliophoran living on setae on the mouthparts of lobsters.

9. Phylum Cycliophora
Feed by collecting bacteria or bits of food dropped from their lobster host on a ring of compound cilia that surrounds the mouth
Simple body plan where the mouth leads to U-shaped gut ending with an anus that opens outside the ciliated ring
Acoelomate body
Cellular epidermis surrounded by a cuticle
Life cycle has sexual and asexual phases
Feeding animals form internal buds called Pandora larvae

10. Phylum Cycliophora
Pandora larvae become new feeding individuals upon release and cloned members occupy vacant areas on the lobster mouthparts
In sexual reproduction, male larvae is released and settles atop another animal that houses a female larvae
Male larvae produce secondary males with reproductive organs and internal fertilization occurs as secondary male mates with a female larva leaving the body of a feeding animal
Once fertilization occurs, Chordoid larva develops inside the body of its mother and consuming it

11. Phylum Entoprocta Characteristics
About 150 species occur worldwide Usually in marine environments
Less than 5 mm long and mostly microscopic
May be solitary or colonial, sessile and on stalks
All ciliary feeders.
Urnatella gracilis common freshwater species in North America while other species are marine.

12. Figure 15.3 A, Urnatella sp., a freshwater entoproct, forms small colonies of two or three stalks from a basal plate. B, Loxosomella sp., a solitary entoproct. Blue arrows indicate the direction of water movement. C, A live Loxosomella sp.

13. Phylum Entoprocta Form and Function
Body or calyx is cup shaped and bears a circular crown of ciliated tentacles
Attaches by a stalk with adhesive glands
Body wall has a cuticle, cellular epidermis and longitudinal muscles
Tentacles (3-30) and stalk are continuations of the body wall
Tentacles are ciliated on the lateral and inner surfaces and can roll inward to protect the mouth and anus but cannot be retracted into the calyx

14. Phylum Entoprocta
Gut is U-shaped with both mouth and anus opening within the circle of tentacles
Long cilia on sides generate current bringing in particles
Short cilia on inner surfaces capture food and direct it to mouth
Digestion and absorption occur in stomach and intestines
Pseudocoel is fluid filled with gelatinous parenchyma with flame bulb protonephridia and ducts that unite and empty into mouth

15. Phylum Entoprocta
Well-developed nerve ganglion on the ventral side of stomach
Body surface has sensory bristles
No circulatory or respiratory organs
Some are monoecious, some dioecious, and some produce sperm first and later eggs called protandrous hermaphrodites
Fertilized eggs develop in a brood pouch between gonopore and anus
Has modified spiral cleavage leads to trochophore-like larva

16. Phylum Ectoprocta Characteristics
Contains aquatic animals that often encrust hard surfaces
Most are sessile, some slide slowly, and others crawl actively across surfaces
Mostly colony builders with each member less than 0.5 mm in length
Colony members are called zooids that feed by extending lophophores into surrounding water to collect tiny particles
Zooids also secrete exoskeleton in which they live in called zoecium

17. Figure A, A colony of Membranipora, a marine encrusting bryozoan (Ectoprocta). B, Portion of a colony of an encrusting bryozoan with lophophores extended.

18. Phylum Ectoprocta
Zoecium may be gelatinous, chitinous, or stiffened with calcium and possibly impregnated with sand that can be boxlike, vaselike, oval, or tubular in shape
Approximately 4500 living species
Inhabit both shallow freshwater and marine habitats
Some marine colonies form limy encrustations on seaweed, shells, and rocks
Others form fuzzy or shrubby growths or erect branching colonies
Freshwater colonies may form moss-like colonies on stems of plants or on rocks

19. Figure 15. 5 Colonies of marine ectoprocts
Figure Colonies of marine ectoprocts. A, The zooids are encrusting in this lacy colony of Membranipora tuberculata. B, Bugula neritina has upright, branching colonies.

20. Phylum Ectoprocta
Ectoprocts were also called Bryozoans (moss animals) and are differentiated from Entoprocta by the location of the anus on the outside of the tentacular ring around the mouth.
Form and Function
Zooids consists of a feeding polypide and a case-forming cystid
Polypide includes the lophophore, digestive tract, muscles, and nerve centers
Cystid includes the body wall of an animal, together with its secreted exoskeleton

21. Phylum Ectoprocta
Polypides pop up to feed, but withdraw quickly at the slightest disturbance into its chamber with a trapdoor called operculum
To extend tentacular crown, muscles contract and increases hydrostatic pressure within the body cavity that forces the lophophore out
Other muscles contract to withdraw crown to safety back into the chamber with great speed.
To feed, the lophophore is extended and tentacles spread out into a funnel
Cilia on tentacles draw water into funnel and food particles caught by cilia are drawn into the mouth by the pumping action of the muscular pharynx and by the action of the cilia

22. Figure A, Ciliated lophophore of Electra pilosa, a marine ectoproct. B, Plumatella repens, a freshwater bryozoan (phylum Ectoprocta).

23. Phylum Ectoprocta
Marine ectoprocts have circular lophophore ridge while freshwater species have U-shaped lophophore with a protocoel and flap over the mouth called epistome
Digestion begins extracellularly in the stomach and completed intracellularly in the intestine in a complete gut system.
Respiratory, vascular, and excretory organs absent with gas exchange through body surface using coelomic fluid for transport
Ganglionic mass and a nerve ring around the pharynx with no sense organs.

24. Phylum Ectoprocta
Coelomocytes engulf and store waste materials within the coelomic fluid
Ectoproct colonies usually contain feeding individuals but sometimes have non-feeding members called heterozooids
Aviculariums are modified zooids that resemble bird beaks and can snap at small invading organisms that approach the colony
Vibraculum have long bristles that sweep away foreign particles

25. Phylum Ectoprocta Ectoprocts are mostly hermaphroditic
Some species shed eggs into seawater, but most brood their eggs
Brooding occurs within coelom and some have an external chamber called an ovicell
Sometimes embryos proliferate asexually from the initial embryo in a process called polyembryony
Cleavage is radial but mosaic
Larva of nonbrooding species have a functional gut and swim for a few months before settling
Larva of brooding species do not feed and settle after a brief free-swimming existence

26. Phylum Ectoprocta
Larvae attach to substratum by secretions from an adhesive sac, then metamorphose to become an adult form
New colonies begin from this single metamorphosed primary zooid, called an ancestrula
Ancestrula undergoes asexual budding to produce many zooids of a colony
Freshwater ectoprocts undergo budding that produces statoblasts which are hard, resistant capsules containing a mass of germinative cells
Statoblasts occur in the summer and fall that eventually give rise to polypides and later forming new colonies

27. Figure 15.7
Statoblast of a
freshwater ectoproct
Cristatella sp.

28. Phylum Brachiopoda Characteristics
Ancient group that were called lamp shells
Approximately 325 living species with fossil records of up to 12,000 species
Generally attached, bottom-dwelling, marine forms that inhabit shallow water but are found nearly in all ocean depths
Externally resemble bivalves but have dorsal and ventral valves instead of lateral valves in clams
Attached to substrate directly or by fleshy stalk, called the pedicel

29. Figure Brachiopods.

30. Phylum Brachiopoda
Brachiopods have ventral valve (pedicel) that is slightly larger than dorsal valve (brachial) with an end projecting out like a beak.
For many species, the pedicel valve is shaped like a classic oil lamp of ancient Greece hence the name “lamp shells”
Shell valves distinguish the two classes of brachiopods
Articulata have connecting hinge with an interlocking tooth-and-socket arrangement
Inarticulata have no hinge and held together by muscles

31. Phylum Brachiopoda
Body occupies only the posterior space between valves
Extensions of the body wall form mantle lobes that line and secrete the shell
Have large horseshoe-shaped lophophore in the anterior mantle
Ciliated tentacles are involved in feeding and respiration with ciliary water currents carrying food between the valves.
Tentacles catch food and move particles to mouth via lophophore which can also absorb dissolved nutrients.

32. Phylum Brachiopoda
Three coelomic cavities like protocoel, mesocoel and metacoel are present
Coelomocytes ingest wastes and are expelled by pair of nephridia that open into coelom and empty out to the mantle
Have open circulatory system with contractile heart
Nerve ring with small dorsal and large ventral ganglion
Most have separate sexes and fertilization is external while some brood their young

33. Phylum Brachiopoda
Cleavage is radial with coelom and mesoderm formation in some as being enterocoelic.
In articulates, metamorphosis of larvae occurs after they are attached by pedicel
In the inarticulates, juveniles resemble small brachiopods with coiled pedicel in the mantle cavity and no metamorphosis.

34. Figure 15. 9 Phylum Brachiopoda. A, An articulate brachiopod
Figure Phylum Brachiopoda. A, An articulate brachiopod. B, Feeding and respiratory currents. Blue arrows show water flow while black arrows indicate food movement.

35. Phylum Phoronida Characteristics
Contains about 20 species of small, wormlike animals that range from few mm to 30 cm
Most live on substrate of shallow coastal waters, especially in temperate seas
Each worm secretes a leathery or chitinous tube in which it lies free, but never leaves the tube
Tubes may be anchored singly or in a tangled mass on rocks, shells, or pilings or buried in sand

36. Figure 15.10
Internal structure of
Phoronis (phylum
Phoronida).

37. Phylum Phoronida
Phoronids thrust out tentacles on lophophore for feeding but withdraw into the tube when disturbed
Lophophore has two parallel ridges curved in a horseshoe shape with mouth in between the two ridges
Cilia in tentacles direct water currents toward groove between two ridges
Plankton and detritus caught in current become entangled in mucus and are carried by cilia to mouth

38. Phylum Phoronida
Anus lies dorsal to mouth outside of lophophore next to nephridiopore
Water leaving the lophophore passes over the anus and nephridiopores to remove wastes
Cilia in stomach of the U-shaped gut aid in food movement
Body wall consists of cuticle, epidermis, and both longitudinal and circular muscles
Protocoel is present as small cavity in epistome
Septum separates mesocoel and metacoel

39. Phylum Phoronida
Extensive system of contractile blood vessels in functionally closed circulatory system but no heart
Blood contains hemoglobin within nucleated cells
Nerve ring sends nerves to tentacles and body wall with a diffuse system that lacks distinct ganglion or brain
Has giant motor fiber in the epidermis and epidermal nerve plexus supplies the whole body

40. Phylum Phoronida
Have monoecious and dioecious species with one species reproducing asexually
Fertilization may be internal or external
Cleavage is radial and coelom formation is highly modified enterocoelous form with the blastophore forming the mouth
Free swimming ciliated larvae called actinotroch will sink into the sea floor and metamorphoses to an adult that secretes a tube and remain sessile

41. Phylum Nemertea Characteristics
Often called ribbon worms that are thread shaped or ribbon-shaped bilaterally symmetrical triploblastic worms
Have a long muscular tube, the proboscis used to grab prey
Over 1000 species and most are less than 20 cm long but some get to several meters
Nearly all marine with some brightly colored while others are dull and live in secreted gelatinous tubes.

42. Figure 15.11 Ribbon worm Amphiporus bimaculatus (phylum Nemertea)

43. Phylum Nemertea Epidermis is ciliated with many gland cells
Excretory system has flames cells; several have rhabdites
Mostly dioecious with ciliated larvae resembling trochophores
Adult has an anus, producing a complete digestive system that is more efficient with ingestion and defecation occurring at the same time.
Simplest animals with a blood-vascular system
Mostly active predators; some scavengers

44. Figure 15.12 A, Structure of female nemertean worm Amphiporus sp.
B, Amphiporus, with proboscis extended to catch prey.

45. Figure Baseodiscus is a genus of nemerteans whose members typically measure several meters in length.

46. Phylum Nemertea Form and Function
Slender and fragile with body wall that has ciliated columnar cells and layers of circular and longitudinal muscles
Move by gliding over slime track or by undulatory swimming
Mouth is anterior and ventral with complete digestive tract extending along body and ends in the anus
Digestion is extracellular in the gut lumen with cilia moving food along intestines

47. Figure 15. 14 A, Cross section of female nemertean worm
Figure A, Cross section of female nemertean worm. B, Excretory and circulatory systems of nemertean worm.

48. Phylum Nemertea
Some species detect prey when physically near and use proboscis hiding in a cavity called the rhynchocoel to seize it.
Proboscis is long, blind muscular tube that opens at anterior end called proboscis pore which is above the mouth
Muscular pressure on fluid in the rhynchocoel causes the proboscis to be everted rapidly through the proboscis pore and exposes a sharp barb called a stylet that stabs prey
Stylet release toxins into prey and sticky slime covered proboscis coils around it and moves to mouth for swallowing

49. Phylum Nemertea
Nemerteans have true circulatory system and blood flow is irregular due to contraction of vessels and general body movements
Flame bulb protonephridia associated with circulatory system to achieve true excretory role of removing wastes
Have nerve ganglia with one or more pairs of longitudinal nerve cords
Reproduce via fragmentation and regeneration plus a wide range of sexual reproductive strategies

50. Phylum Nemertea
Nemerteans are mostly dioecious and fertilization is often external but some are hermaphroditic and may have internal fertilization
A few species have ovoviviparous development that has egg develop into live young before being release by the parent
Phylogeny of Nemerteans is still debatable due to larval development patterns and coelom formation issues

51. Phylogeny and Diversification
Molecular characters have changed the phylogeny of Lophophores and its associated groups
Developmental characters associated with spiral cleavage are presumed to be ancestral to the clade
Spirally cleaving embryos have mosaic cleavage patterns and mesoderm formation from particular endoderm cells
But many members of the Lophophores do not follow these features and prevent clear placement into specific clades and groups

52. Phylogeny and Diversification
Placement of Nemerteans are contentious and highly debatable.
Nemerteans used to be with Platyhelminthes due to flame cells and cilated epidermis but the presence of complete digestive tract and reversible proboscis in a unique coelomic cavity counters this original grouping
Nemerteans coelomic cavity above the digestive tract sets them apart form other coelomate animals