Z250 Platyhelminthes Clade (2017)

Zoology 250 Phylogenetic Trees (2017)

(acoel flatworm)

(polyclad flatworm)

PHYLUM PLATYHELMINTHES
(Clade for classes and Turbellarian orders
from Ruppert et al. 2004 p. 250;
4 turbellarian orders are omitted;
see also Alternative Molecular Phylogenies)

(trematode fluke)

(cestode tapeworm head)

                  Cl. T
     ==================U=============    Or. Catenulida (small, slender, free-living, gut= simple sac)
<<=1=|                  R
     | ==========2a======B===========    Or. Acoela (small body size, gutless)
     ==|                  E
       |   =======2c=======L=========    Or. Polycladida (large body size, multi-branched gut)
       =2b=|                L
           |   ====2e========A=======    Or. Tricladida (the planarians; 3-branched gut)
           =2d=|              R
               |   ==2g========IA====    Or. Rhabocoela (small body size, unbranched gut
               =2f=|
                   |     ======4===== Cl. Trematoda (endoparasitic flukes)
                   ==3===|
                         |     ==6=== Cl. Monogenea (ectoparasites of aquatic vertebrates)
                         ==5===|
                               ==7=== Cl. Cestoidea (endoparasitic tapeworms)

Back to Zool 250 tree for animal phyla or Protostomia

TRAITS SUPPORTING EACH CLADE(** plesiomorphic- a primitive state, not unique to clade) AND HIGHER TAXA:

1: a) mid-ventral mouth**
b) blind gut**
c) protonephridia**
d) protonephridial terminal cell has 2 flagella
e) coelom & blood vascular system absent**
f) ciliated epidermis**
g) multiciliated cells**
h) epidermal gland cells extensive
i) monociliated sperm
j) hermaphroditic (unclear if valid trait)
k) archoopheran reproductive system

2a: a) no gut**
b) simple pharynx**
c) lack protonephridia
d) no distinct gonads (gametes from parenchyma)

2b: a) rhabdites
b) bi-ciliated sperm (present in allhigher groups)
c) gut cavity present
d) plicate pharynx
e) protonephridial terminal cell has 4 flagella (present in all higher groups)
f) unique nucleotide triplet for Asparagine (Telford et al. 2000, PNAS 97:11359)

2c: a) gut has multiple branches
b) pair of anterior tentacles (some)
c) multiple gonads among branches of gut

2d: a) neoopheran reproductive system (present in all higher groups)
b) typical 'spiral' cleavage lost

2e: a) gut has three branches

2f: a) bulbous pharynx

2g: a) gut has single cavity (unbranched)

3= NEODERMATA: a) syncytial, non-ciliated epidermis
b) terminal mouth (also some rhabdocoels)
c) paired intestinal cecae

4= TREMATODA: a) oral & mid-ventral sucker
b) complex=indirect life cycle (1-2 intermediate hosts)
c) anaerobic metabolism

5: a) distinct attachment hooks in larva

6= MONOGENEA: a) haptor
b) simple=direct life cycle** (no intermediate hosts)

7= CESTOIDEA: a) scolex
b) strobila (=chain of proglottids)
c) mouth and gut absent
d) reproductive system repeated in each proglottid
e) complex=indirect life cycle (1 or more intermediate hosts)

TWO ALTERNATIVE MOLECULAR PHYLOGENIES FOR PARAPHYLETIC PLATYHELMINTHES (OPTIONAL, for information only)

ALTERNATIVE #1: ACOELS AS SISTER GROUP TO REMAINING BILATERIA (from Egger et al. 2009 PLOS1 4(5)e5502)

     =========================================== Porifera (sponges)
     |
     |  ======================================== Placozoa (placozoans, Trichoplax)
=====|  |
     |  |   ==================================== Cnidaria (jellyfish, anemones, corals, etc.)
     ===|   |
        |   |     ============================== ACOELOMORPHA (acoel flatworms)
        ====|     |
            |     |     ======================== remaining Platyhelminthes (flatworms, tapeworms, etc.)
            ======|  ===|
                  |  |  ======================== remaining PROTOSTOMIA
  B= BILATERIA    =B=|
                     =========================== DEUTEROSTOMIA

ALTERNATIVE #2: ACOELS AS A BASAL BRANCH OF DEUTEROSTOMIA (from Philippe et al. 2011 Nature 470:255-258)

     =========================================== Porifera (sponges)
     |
     |  ======================================== Placozoa (placozoans, Trichoplax)
=====|  |
     |  |   ==================================== Cnidaria (jellyfish, anemones, corals, etc.)
     ===|   |
        |   |           ======================== remaining Platyhelminthes (flatworms, tapeworms, etc.)
        ====|        ===|
            |        |  ======================== remaining PROTOSTOMIA
            =====B===|
  B= BILATERIA       |  ======================== ACOELOMORPHA (acoel flatworms)
                     ===|
                        ======================== remaining DEUTEROSTOMIA

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