Z250 (2004)

Zoology 250 Phylogenetic Trees (2004)

(acoel flatworm)

(polyclad flatworm)

PHYLUM PLATYHELMINTHES

(Clade for classes and Turbellarian orders
from Nielson 1995 p. 216.)

(trematode fluke)

(cestode tapeworm head)

                  Cl. TUR
       ==========2a======B===========    Or. Acoela (small body size, gutless)
<<=1===|                  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 version of tree for animal phyla or Protostomia.

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

1: a) mid-ventral mouth**
b) blind gut**
c) protonephridia**
d) coelom & blood vascular system absent**
e) ciliated epidermis**
f) multiciliated cells**
g) epidermal gland cells extensive
h) monociliated sperm
i) hermaphroditic (unclear if valid trait)
j) 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 all higher groups)
c) gut cavity present
d) plicate pharynx
e) 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: 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 & gut absent
d) reproductive system repeated in each proglottid
e) complex=indirect life cycle (1 or more intermediate hosts)