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The “Lophophorates” Phylum Bryozoa Phylum Phoronida Phylum Brachiopoda

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Presentation on theme: "The “Lophophorates” Phylum Bryozoa Phylum Phoronida Phylum Brachiopoda"— Presentation transcript:

1 The “Lophophorates” Phylum Bryozoa Phylum Phoronida Phylum Brachiopoda
Once upon a time, there were 3 phyla that had an apparent synapomorphy: the lophophore, a horseshoe-shaped ring of ciliated tentacles surrounding mouth, used in filter feeding Phylum Bryozoa Phylum Phoronida Phylum Brachiopoda - colonies made of microscopic zooids - worm-like, tube-dwelling; large - 2 shell valves; large

2 Lophophorates on the Tree of Life
Lophophorates were 1st placed in the Deuterostomes, as: - their early embryonic cleavage is radial & indeterminate - body forms with 3 regions and a 3-part coelom However, they also share some Protostome characteristics: - mouth develops from blastopore in one group, Phoronids - larvae of some look like modified trochophores - they can make chitin, a building material not found in Deuterostomes Where does molecular analysis of DNA + protein sequence data place them...?

3 OLD Annelids SCHOOL (WRONG) Arthropods Molluscs Protostomes Nematodes
Platyhelminthes Lophophorates Chaetognaths Deuterostomes Echinoderms Chordates

4 DNA analysis: Lopho’s are protostomes
Comparison of the highly-conserved 18S rRNA gene sequence showed that all 3 lophophorates grouped with protostomes, not with the deuterostomes Proposed clade within protostomes: the Lophotrochozoa - lophophorates, molluscs + annelids; excludes arthropods + nematodes - no synapomorphy; either have a lophophore, or a trochophore larva (not really legit for naming) Halanych et al. 1995

5 Protostomes Spiralia Nematodes Arthropods Deuterostomes Phoronids
Chaetognaths Protostomes Spiralia Nematodes Arthropods Echinoderms Chordates Deuterostomes

6 Spiralia – spiral cleavage of embryos
Phoronids Chaetognaths Lophotrochozoa Spiralia – spiral cleavage of embryos Nematodes Arthropods Ecdysozoa – molting phyla Echinoderms Chordates Deuterostomes

7 Lophotrochozoa Trochozoa phyla with a trochophore larval stage
Phoronids Chaetognaths Lophotrochozoa Brachipoda Nemertea Mollusca Annelida Trochozoa phyla with a trochophore larval stage Platyhelminthes Rotifera Platyzoa Bryozoans Entoprocts Cycliophorans Spiralia Polyzoa

8 The former “lophophorates” are scattered among all the major clades
Phoronids Chaetognaths The former “lophophorates” are scattered among all the major clades Brachipoda Nemertea Mollusca Annelida  they are not a monophyletic group !! Platyhelminthes Rotifera Bryozoans Entoprocts Cycliophorans Spiralia

9 All recent molecular studies support this version of protostomes
Spiralia: animals with spiral cleavage of their embryos Platyzoa: flatworms, rotifers Polyzoa: bryozoans, entoprocts, cycliophorans Trochozoa: animals with a trochophore stage  annelids, molluscs, nemerteans, brachiopods Ecdysozoa: animals with an external cuticle, that molt to grow  nematodes, arthropods, minor phyla Phoronids Chaetognaths placement uncertain; phoronids are probably trochozoans Note: all of these group names are names of clades, but do not correspond to phylum, class, order ranks

10 Lophophorate characteristics
Body divided in 3 parts, each with its own coelomic space: This 3-part body/coelom structure is typical of deuterostomes like us... probably an ancestral feature kept by deuterostomes and lophophorates, which changed in the Spiralians Anterior Coelomic space Body region Protocoel Prosome Mesocoel Mesosome Posterior Metacoel Metasome

11 The Lophophore 3 phyla have a lophophore, a circle of tentacles used
in suspension feeding Ciliated growth of tentacles arising from mesosome (middle coelomic compartment) - tentacles contain fingers of coelom - surround mouth, but not anus Is not a synapomorphy; evolved independently 2-3 times (= homoplasy)

12 Lophophore Function Cilia on lophophore tentacles generate a feeding current - cilia catch particles, bounce them back and forth to mouth - each tentacle has 1 row of frontal cilia and 2 rows of lateral cilia

13 Phylum Bryozoa - Prosome reduced/absent; mesosome fills lophophore +
5,000 spp. - Prosome reduced/absent; mesosome fills lophophore + connects to metasome, which contains viscera (organs) - Colonial, made up of individual zooids that bud asexually zooids bilaterally symmetric, often polymorphic U-shaped gut, anus outside lophophore No excretory or circulatory systems; whole body of an individual zooid may be reduced to “brown body” + excreted - Hermaphrodites, as a colony; gonads simple, temporary - Undergo radial cleavage (like deuterostomes); blastopore does not become mouth or anus (unique to them) Most produce lecithotrophic larvae that settle rapidly; important members of fouling communities

14 Polypide = soft tissue + lophophore
Zooid = exoskeleton + polypide Autozooids = feeding Heterozooids = no lophophore, do other functions for colony Compare & contrast bryozoans with hydrozoans (Cnidaria) – What convergent adaptations for colonial life do the 2 groups show?

15 Heterozooids = no lophophore,
do other functions for colony Ovicells – incubators for developing embryos - sperm taken up from seawater, used to fertilize eggs - parental zooid degenerates, forming nutritive tissue chamber for fertilized eggs Avicularia – giant claws used to defend colony - polypide reduced to a few large muscles - claw is modified operculum - prevents fouling by larvae + spores of other organisms

16 colony of inter-connected zooids swimming larva ancestrula asexual
reproduction Colony starts as a metamorphosed larva, which grows into one original zooid, the ancestrula ancestrula then clones itself to form whole colony, asexually

17 Class Stenolaemata - most extinct - tubular, calcified exoskeleton

18 Bryozoan Groups Class Stenolaemata Class Gymnolaemata
- zooids connected by funiculus (a coelomic link) Order Cheilostomata - openings covered by opercula - embryos usually brooded in ovicells - avicularia: claws function in defense Order Ctenostomata - cylindrical zooids, attached by stolon - no operculum, ovicells or avicularia

19 Class Gymnolaemata Order Ctenostomata - cylindrical zooids funiculus
- flexible, chitinous exoskeleton - zooids sprout from a horizontal runner called the stolon (at some distance from each other) Funiculus = coelomic connection between zooids (may even link stomachs) funiculus

20 Class Gymnolaemata Order Ctenostomata
Extend lophophore by hydrostatic pressure: - parietal muscles contract, pressurizing coelom - fluid extends lophophore, expands tentacles Retract lophophore by muscle action: - lophophore pulled in by retractor muscles - collar folds over withdrawn tentacles collapses over tentacles compare and contrast feeding in this group with sipunculan worms!

21 Class Gymnolaemata Order Cheilostomata - polymorphic zooids
- exoskeleton made of chitin + calcium carbonate - non-stoloniferous growth: walls of the zooids are attached to each other (grow in a sheet)

22 Class Gymnolaemata Order Cheilostomata
- hard casing causes a problem: how to pressurize coelom? - solution: flexible frontal membrane on top - muscles pull membrane down, pressurizing coelom lophophore extends In most successful group, membrane = the ascus - internal, for protection; outer wall is solid - pore lets seawater in when ascus is pulled down

23 Schizoporella unicornis
showing orange opercula covering zooids

24 lophophores extended Eurystomella bilabiata, only food of the
“Hopkin’s Rose” sea slug lophophores extended

25 Bugula neritina - common fouling organism, worldwide Contains defensive compounds, the bryostatins - made by a unique bacterial symbiont - chemicals protect the large, lecithotrophic larvae from predation during their brief planktonic journey - in clinical trials as an anti-cancer drug

26 Bryozoans are sister to a clade composed of 2 phyla that
were never even grouped as “lophophorates” Platyhelminthes Rotifera Platyzoa Polyzoa Bryozoa Cycliophora Entoprocta - based on molecular analysis of protein sequences

27 Phylum Entoprocta - solitary or colonial filter feeders
150 species - solitary or colonial filter feeders - feed with anterior ring of ciliated tentacles, but anus opens inside the ring (ento = within, procta = anus) - no blood vessels, U-shaped gut - spiral, determinate embryonic cleavage (typical protostome kind) - some species have trochophore-like larvae embryos + larvae are like other protostomes, adults are like bryozoans.. close relatives that develop quite differently

28 water moves through the ring of ciliated tentacles in the
opposite direction of lophophore flow Lophophorate water water Entoproct

29 developing larvae may be found
attached to inside of calyx Phylum Entoprocta family Pedicellinidae Barentsia benedeni calyx, with fringe of tentacles stalk may have up to 12 joints on older individuals

30 Phylum Cycliophora ~5 species Close-up of mouthparts of
Norwegian lobster, showing… Symbion pandora

31 Phylum Cycliophora First reported in 1995 Entire phyla are still
waiting to be discovered used to stick to lobster mouth

32 Phylum Phoronida - worm-like body inside a chitin tube
2 genera 14 species - worm-like body inside a chitin tube - body has a flappy prosome, mesosome w/ lophophore, and an elongated trunk (metasome) - U-shaped gut; mouth and anus very close together 1 pair of metanephridia, closed circulatory system - gonads simple, temporary; separate sexes or hermaphrodites - blastopore becomes mouth (protostome character) unique actinotroch larvae

33 - lophophore is a double row of tentacles
- each tentacle contains blood vessel for gas exchange, extension of coelom - food particles brought into ring by current; then trapped in mucus lining food groove - gametes proliferate in metacoel of trunk, released through nephridia, or ruptured out of tentacle ends .. similar to many annelid worms; is this a synapomorphy or a case of convergent evolution?

34 Phoronis vancouverensis
Few species = not evolutionarily successful Can be very ecologically important, however; tubes can form dense aggregations on local mudflats, creating habitat

35 Phoronis australis commensals that attach to the tubes made by cerianthids, a group of tube-building anemones that live in soft-sediments

36 Actinotroch larvae - distinctive flattened head, body ringed with fat tentacles - ring of cilia at base of body

37 Phylum Brachiopoda - body enclosed between 2 valves (dorsal + ventral)
350 living species 30,000 fossil species Phylum Brachiopoda - body enclosed between 2 valves (dorsal + ventral) - live cemented to bottom, or dig with ventral foot-like pedicle - valves lined by mantle, creating mantle cavity (as in molluscs) - U-shaped gut, with or without anus 1-2 pairs of metanephridia, open circulatory system - separate sexes; temporary gonads - blastopore closes; mouth + anus form secondarily

38 valves house lophophore
inside mantle cavity

39 Brachiopod Filter Feeding
ciliary motion water flow - Water passes over lateral cilia bands, which send particles to frontal bands by localized beat reversal - Frontal cilia then re-direct particles to food groove

40 Class Inarticulata Class Articulata
- shells may be equal, - shells usually unequal especially in burrowers - valves not hinged; - valves hinged: ventral teeth attached by muscles lock into dorsal socket - lophophore w/out skeleton - lophophore w/ skeleton - anus present - no anus

41 Articulate Brachiopod
- Ventral valve bears teeth that lock into dorsal valve socket - Adductor muscles close valves; diductors open valves - contrast w/ bivalve, where springy ligament forces shell valves open if adductor muscles relax

42 Brachiopod vs. Bivalve umbo is dorsal top valve is dorsal ventral

43 Brachiopod vs. Bivalve evolutionary loser evolutionary winner
350 living spp ,600 living spp. Bivalves and brachiopods compete for the same resources; bivalves have been come dominant, while most brachiopods went extinct Key bivalve innovation may have been the mantle fusing into a siphon for drawing water into the shell

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