HIERARCHICAL CLASSIFICATION OF THE PHYLUM PLATYHELMINTHES (GEGENBAUR 1859)
| EUKARYA> UNIKONTA> OPISTHOKONTA> ANIMALIA> METAZOA> BILATERIA> PROTOSTOMATA> SPIRALIA> PLATYZOA> PLATYHELMINTHES |
PLATYHELMINTHES LINKS
| The following taxonomy is modified from Valentine (2004) and Brusca and Brusca (2003). Descriptions of the following taxa were taken from Margulis and Schwartz (1998), Barnes (1984), Brusca and Brusca (2003), Storer and Usinger (1965), and Walker and Anderson (2001). |
CLASS TURBELLARIA (12 ORDERS)
- Mostly free-living flatworms with a ventral mouth,
eversible pharynx
(text with tooltip)
The eversible pharynx is opening to the gut and feeding structure in turbellarians.
(variations in this structure form the basis for ordinal differentiation) in most species. Gut lobed or branched. Cellular and ciliated epidermis; with single bundles of
rhabdites
(text with tooltip)
Rhabdites are certain epidermal secretion droplets that have a defined layered ultrastructure in certain Platyhelminthes.
(structures of unknown function). Usually the head has sensory organs such as ocelli. The common planarian (Dugesia) has the signature “arrowhead” appearance due to the laterally-projecting auricles on its head.
- Amphiscolopus, Dugesia (Planaria), Stenostomum, Haplopharynx, Gnosnesma, Prorhynchus, Macrostomum, Microstomum, Flagellophora, Meara, Nemertoderma, Eurylepta, Hoploplana, Leptoplana, Notoplana, Planocera, Prostheceraeus, Pseudoceros, Stylochus, Thysanozoon, Plagiostomum, Urostoma, Proplicastoma, Nemertoplana, Octoplana, Taboata, Callastoma, Graffilla, Pterastricola, Kytorhynchus, Mesostoma, Typhlorhynchus, Cheliplana, Cystiplex, Gnathorhynchus, Gyratrix, Temnocephala, Bdelloura, Bipalium, Crenobia, Geoplana, Polycelis, Procotyla.
CLASS MONOGENEA (2 SUBCLASSES, EACH WITH A SINGLE ORDER)
- Flat, leaf-like flukes, mostly ectoparasites on fish. Eggs hatch into onchomiricidia (text with tooltip) An onchosphere (also called a coracidium) is the first encapsulated larval stage of certain tapeworms. It is ciliated and has 6 hooks. larvae which attach to host and change into adult. Body with organs of attachment. Covered with cuticle (text with tooltip) Cuticle is an acellular covering that is secreted by the epithelium. . Paired excretory pores and well-developed gut. The two subclasses are separated by the type of posterior attachment organ (the opisthaptor).
- SUBCLASS MONOPISTHOCOTYLEA
- The posterior attachment organ very simple, usually of a single sucker, or a sucker divided by a septum. Oral sucker absent or reduced.
- Polystoma, Gyrodactylus.
- The posterior attachment organ very simple, usually of a single sucker, or a sucker divided by a septum. Oral sucker absent or reduced.
- SUBCLASS POLYOPISOTHOCOTYLEA
- The posterior attachment organ complex with many suckers. No oral sucker.
- Diplozoon
- The posterior attachment organ complex with many suckers. No oral sucker.
CLASS TREMATODA (6 ORDERS DISTRIBUTED THROUGH 2 SUBCLASSES)
- Endoparasitic flukes, mostly of vertebrates. Life cycles complex ( miracidia (text with tooltip) Miracidia (miracidium, sing.) are the first larval stages in digenean flukes. They emerge from the egg as free-swimming ciliated larvae and infect snails in which cercariae are formed. , cercariae, metacercariae (text with tooltip) Metacercariae (metacercaria, sing.) are the final larval stages in digenean flukes. They usually are formed when the cercaria encysts. Metacercariae are the stages that infect the primary (vertebrate) hosts. ) most with two or more hosts (one usually a mollusk) and several larval stages, one or more of which reproduce asexually. Cylindrical or leaf-shaped with a well-developed gut. Single, posterior excretory pore. Cuticle-covered surface, and one or two suckers.
- SUBCLASS DIGENEA
- Usually with 2-3 hosts. First host in the lifecycle (from the egg) is a mollusk. Final host a vertebrate.
- Echinostoma, Fasciola, Microphallus, Opisthorchis (Clonorchis), Sanguinicola, Schistosoma.
- Usually with 2-3 hosts. First host in the lifecycle (from the egg) is a mollusk. Final host a vertebrate.
- SUBCLASS ASPIDOGASTREA
- This small group is like the Digeneids, usually a very large sucker that usually is divided to form a series of suckers that cover the ventral part of the animal. Like the digeneids, they have 1-2 hosts and a ciliated larval form. There seems to be low host specificity, but the first host is a mollusk and the final host is a fish or a turtle.
- Rugogaster, Stichocotyle, Multicalyx, Rohdella, Cotylogaster, Aspidogaster, Synchnocotyle.
- This small group is like the Digeneids, usually a very large sucker that usually is divided to form a series of suckers that cover the ventral part of the animal. Like the digeneids, they have 1-2 hosts and a ciliated larval form. There seems to be low host specificity, but the first host is a mollusk and the final host is a fish or a turtle.
CLASS CESTODA (2 SUBCLASSES)
- These are the tapeworms, platyhelminth parasites of the guts of vertebrates. The body is covered by a cuticle. Anterior end of most with attachment organs. In many systems, the two subclasses are raised to class status.
- SUBCLASS CESTODARIA (2 ORDERS)
- Flatworms without mouths or guts, endoparasites of fish and turtles. Cuticle-covered body with single set of male and female organs. Sometimes with anterior suckers, never a
scolex
(text with tooltip)
A scolex is the anterior or attachment structure of a tapeworm.
. First larval stage an
onchosphere
(text with tooltip)
An onchosphere (also called a coracidium) is the first encapsulated larval stage of certain tapeworms. It is ciliated and has 6 hooks.
(lycophore) with 10 hooks.
- Amphilina, Gyrocotyl, Gyrometra.
- Flatworms without mouths or guts, endoparasites of fish and turtles. Cuticle-covered body with single set of male and female organs. Sometimes with anterior suckers, never a
scolex
(text with tooltip)
A scolex is the anterior or attachment structure of a tapeworm.
. First larval stage an
onchosphere
(text with tooltip)
An onchosphere (also called a coracidium) is the first encapsulated larval stage of certain tapeworms. It is ciliated and has 6 hooks.
(lycophore) with 10 hooks.
- SUBCLASS EUCESTODA (12 ORDERS)
- Endoparasitic flatworms in guts of vertebrates and in a variety of intermediate hosts. Body without a gut or mouth. Anterior end usually with a
rostellum
(text with tooltip)
A rostellum is a prominent rounded apex on the scolex of some tapeworms. It also is a beak-like tubular mouth part in some sucking insects.
and a scolex followed by a short neck and
strobila
(text with tooltip)
Strobila (strobilae, pl.) are structures that bud medusae in certain Cnidarians. Also, a strobila is the name of the pseudosegmented proglottid portion of a tapeworm.
, a linear series of
proglottids
(text with tooltip)
A proglottid is one of the pseudosegments that make up the strobila of a tapeworm. Typically, they are hermaphroditic and are released when gravid.
. Each proglottid develops a set of reproductive organs and matures by filling with eggs. Eggs develop into onchosphere larvae with 6 hooks.
- Diphyllobothrium, Taenia, Dipylidium, Hymenolepis, Moniezia, Echinococcus
- Endoparasitic flatworms in guts of vertebrates and in a variety of intermediate hosts. Body without a gut or mouth. Anterior end usually with a
rostellum
(text with tooltip)
A rostellum is a prominent rounded apex on the scolex of some tapeworms. It also is a beak-like tubular mouth part in some sucking insects.
and a scolex followed by a short neck and
strobila
(text with tooltip)
Strobila (strobilae, pl.) are structures that bud medusae in certain Cnidarians. Also, a strobila is the name of the pseudosegmented proglottid portion of a tapeworm.
, a linear series of
proglottids
(text with tooltip)
A proglottid is one of the pseudosegments that make up the strobila of a tapeworm. Typically, they are hermaphroditic and are released when gravid.
. Each proglottid develops a set of reproductive organs and matures by filling with eggs. Eggs develop into onchosphere larvae with 6 hooks.
| LITERATURE CITED Barnes, R. D. 1980. Invertebrate Zoology. Saunders College/Holt, Rinehart and Wilson, Philadelphia. Barnes. R. S. K. 1984a. Kingdom Animalia. IN: R. S. K. Barnes, ed. A Synoptic Classification of Living Organisms. Sinauer Associates, Inc., Sunderland, MA. pp. 129-257. Brusca, R. C. and G. J. Brusca. 2003. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass. Buchsbaum, R. 1938. Animals Without Backbones, An Introduction to the Invertebrates. The University of Chicago Press. Chicago. Conway Morris, S. and J. S. Peel. 2008. The earliest annelids: Lower Cambrian polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland. Acta Palaeontol. Pol. 53(1): 137-148. Darwin, C. R. 1881. The Formation of Vegetable Mould, Through the Action of Worms, With Observations on their Habits. John Murray. London. Frelich, L., C. Hale, S. Scheu, A. Holdsworth, L. Heneghan, P. Bohlen, and P. Reich. 2006. Earthworm invasion into previously earthworm-free temperate and boreal forests. Biological Invasions. 8(6): 1235-1245. Giribet, G., C. W. Dunn, G. D. Edgecombe, and G. W. Rouse. 2007. A modern look at the Animal Tree of Life. Zootaxa. 1668: 61-79. Giribet, G., A., A. Okusu, A. R. Lindgren, S. W. Huff, M. Schrodl, and M. K. Nishiguchi. 2006. Evidence for a clade composed of molluscs with serially repeated structures: Monoplacophorans are related to chitons. Proc. Nat. Acad. Sci. USA. 103(20): 7723-7728. Halanych, K. M. 2004. The new view of animal phylogeny. Annu. Rev. Ecol. Evol. Syst. 35: 229-256. Halanych, K. M., T. G. Dahlgren, and D. McHugh. 2002. Unsegmented annelids? Possible origins of four lophotrochozoan worm taxa. Integ. and Comp. Biol. 42: 678-684. Hickman, C. P. 1973. Biology of the Invertebrates. The C. V. Mosby Company. Saint Louis. Margulis, L. and K. Schwartz. 1998. Five kingdoms, an illustrated guide to the phyla of life on earth. 3rd Edition. W. H. Freeman and Company. New York. McHugh, D. 1997. Molecular evidence that echiurans and pogonophorans are derived annelids. Proc. Nat. Acad. Sci. USA. 94: 8006-8009. Meglitsch, P. A. and F. R. Schramm. 1991. Invertebrate Zoology. Oxford University Press, New York, Oxford. Nielsen, C. 2001. Animal Evolution: Interrelationships of the Living Phyla. 2nd Edition. Oxford University Press. Oxford. Pechenik, J. A. 2005. Biology of the Invertebrates. McGraw-Hill. New York. Ruppert, E. E. and R. D. Barnes. 1994. Invertebrate Zoology. 6th edition. Saunders. Ft Worth, TX. Ruppert, E. E., R. S. Fox, and R. D. Barnes. 2004. Invertebrate Zoology: A Functional Evolutionary Approach. Seventh Edition. Thomson, Brooks/Cole. New York. pp. 1-963. Siddall, M. E., E. Borda, and G. W. Rouse. 2004. Toward a tree of life for Annelida. In: Cracraft, J. and M. J. Donoghue, eds. Assembling the Tree of Life. Oxford University Press. Oxford, New York. pp. 237-251. Sigwart, J. D. and M. D. Sutton. 2007. Deep molluscan phylogeny: synthesis of palaeontological and neontological data. Proc. Royal Society B. 274: 2413-2419. Storer, T. I. and R. L. Usinger. 1965. General Zoology. 4th Edition. McGraw-Hill Book Company. New York. Struck, T. H., N. Schult, T. Kusen, E. Hickman, C. Bleidorn, D. McHugh, and K. M. Halanych. 2007. Annelid phylogeny and the status of Sipuncula and Echiura. BMC Evolutionary Biology. 7:57 doi: 10.1186/1471-2148-7-57 Tudge, C. 2000. The Variety of Life, A Survey and a Celebration of all the Creatures That Have Ever Lived. Oxford University Press. New York. Walker, J. C. and D. T. Anderson. 2001. The Platyhelminthes, Nemertea, Entoprocta, and Gnathostomulida. In: Anderson, D.T., ed. Invertebrate Zoology. Oxford University Press. Oxford, UK. pp. 59-85. [L] Valentine, J. W. 2004. The Origin of Phyla. University of Chicago Press. Chicago. 614 pp. Zrzavý, J., P. Ríha, L. Piálek, and J. Janouskovec. 2009. Phylogeny of Annelida (Lophotrochozoa): total-evidence analysis of morphology and six genes. BMC Evolutionary Biology. 9:189 doi: 10.1186/1471-2148-9-189 |
| By Jack R. Holt. Last revised: 01/29/2012 |
