Class Turbellaria (flatworms)
- Major Attributes: True bilateral symmetry. Dorso-ventral flattening of the body. Unsegmented. Ciliated epidermis. System of sheathed nerve fibers.
- Description: Turbellarians are mainly free-living and aquatic, but some are terrestial and live in moist, humid environments.
- Some Interesting Facts: If a flatworm is starved it is capable of shrinking to hatching size and when fed it has the ability to grow back to original size.
- Some Pertinent Books Found in Lamson Library: Buchsbaum, Ralph. 1976. Animals Without Backbones. Chicago: University of Chicago Press. Pennak, Robert W. 1964.
- Laboratory: Draw a planarian (wholemount) along the left side of the page and at proper locations, draw cross-sections of what the body looks like at that location.
- True bilateral symmetry.
- Dorso-ventral flattening of the body.
- Unsegmented.
- Ciliated epidermis.
- System of sheathed nerve fibers.
- Parenchyma between the epidermis and the gastrodermis.
- Some cephalization.
- Blind ending gut.
What are the characteristics of turbellarians?
Spiral cleavage is prevalent. Some turbellarians can reproduce asexually by fission. Regeneration of somatic parts is well documented in Dugesia. Some of the colorful marine polycladids are in demand in the aquarium trade, and Dugesia is a common laboratory animal, but the vast majority of turbellarians are of little economic importance to humans.
What type of epidermis does Turbellaria have?
The mostly free-living, primarily carnivorous, flatworms of class Turbellaria are characterized by a soft epidermis that is ciliated, at least on the ventral surface. The movement of the cilia propels the smaller forms.
What is the structure of the nervous system in turbellarians?
For Turbellarians with a more centralized nervous system (e.g. Planarians), it consists of a simple brain (ganglion), nerve cords as well as a sub-epidermal network of nerves. In these species, the simple brain is built from the thickened anterior part of the ventral cords and is located at the anterior/head region of the organism.
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How do you identify a Turbellaria?
Turbellarians share some important characteristics with other Platyhelminthes. All flatworms are flattened dorsoventrally . They are bilaterally symmetrical , are unsegmented, and are acoelomates , which means they do not have a body cavity.
What makes Turbellaria unique?
Turbellarians are also famous for their ability to regenerate when cut into pieces, and some species reproduce by splitting their bodies into two of these clones.
What is the classification of the Turbellaria?
TurbellariaTurbellaria / Scientific name
What are the main characteristics of flatworm?
The main characteristics of flatworms (Figure below) include:Flatworms have no true body cavity, but they do have bilateral symmetry. ... Flatworms have an incomplete digestive system. ... Flatworms do not have a respiratory system. ... There are no blood vessels in the flatworms.More items...•
What is an example of Turbellaria?
PolycladidaTricladidaPseudoceros bicolorTurbellaria/Lower classifications
What are the characteristics of a free living flatworm?
Physical characteristics acoelomate (no fluid filled body cavity or coelom) bilaterally symmetrical. dorsoventrally flattened. spiral cleavage and mesoderm derived from the 4d cell.
What are 5 characteristics of phylum Platyhelminthes?
Platyhelminthes have the following important characteristics: They are triploblastic, acoelomate, and bilaterally symmetrical. They may be free-living or parasites....Unique Characteristics of PlatyhelminthesPresence of flame cells.Ladder-like nervous system.Presence of parenchyma in the body cavity.Self-fertilization.
What is the meaning of Turbellaria?
Medical Definition of Turbellaria : a class of the phylum Platyhelminthes comprising flatworms that are mostly aquatic and free-living but occasionally live on land or as parasites.
How are flatworms classified and what are their characteristics?
Kingdom: Animalia - Flatworms fall under the animal kingdom that is characterized by multicellular eukaryotic organisms. In some classifications, they are also classified under the basal animal clade Eumetazoa since they are metazoans that fall under the animal kingdom (Kingdom Animalia).
What are the 3 classes of flatworms?
The Phylum: Platyhelminthes includes the flatworms (Planaria, flukes & tapeworms) Three Classes treated here are Turbellaria, Trematoda and Cestoda.
Which of the following is a characteristic of a parasitic flatworm such as a tapeworm?
The parasitic flatworms, such as tapeworms and liver flukes, are included within this large phylum. They are bilaterally symmetrical, triploblastic, they lack an anus, and they have no body cavity other than the gut.
What is a flatworm classified as?
flatworm, also called platyhelminth, any of the phylum Platyhelminthes, a group of soft-bodied, usually much flattened invertebrates.
What are the names of the classes of turbellaria?
Orders of the class Turbellaria recognized by Ruppert and Barnes (1994) are: Nemertodermatida, Acoela, Catenulida, Haplopharyngida, Macrostomida, Polycladida, Lecithoepitheliata, Prolecithophora, Proseriata, Temnocephalida, Rhabdocoela, and Tricaldida.
How many species are in Turbellaria?
Turbellaria. Class Turbellaria has approximately 3000 species in 12 orders. Most are marine and benthic, but some also inhabit fresh water and moist temperate and tropical terrestrial habitats. The order Temnocephalida is entirely commensal or parasitic, but some members of other orders are commensal as well.
What do turbellarians use?
Turbellarians use protonephridia scattered throughout their epidermis for the excretion of metabolic waste. Turbellarians sense their environment with statocysts, chemoreceptors, and photoreceptors. They do not have image-forming eyes, but many species have pigment cells and photoreceptors concentrated into eyespots.
What is the pharynx in a turbellaria?
There is usually a pharynx for introducing food into the gut, and undigested food particles are ejected through the mouth. The final stages of digestion are intracellular. Most members of class Turbellaria are predatory on invertebrates smaller than themselves; the rest are herbivores, ectoparasites, or scavengers.
Can turbellarians reproduce asexually?
Some turbellarians can reproduce asexually by fission. Regeneration of somatic parts is well documented in Dugesia. Some of the colorful marine polycladids are in demand in the aquarium trade, and Dugesia is a common laboratory animal, but the vast majority of turbellarians are of little economic importance to humans.
What do turbellarians eat?
Some species use mucus that may have poisonous or narcotic chemicals to slow or entangle prey. Some have specific diets and feed on sponges, ectoprocts, barnacles, and tunicates. Several species have commensal relationships with various invertebrates and few actually border on being parasitic because they graze on their live hosts. Terrestrial species feed on earthworms and land snails. A few species feed on microalgae that may be incorporated into the body, forming a symbiotic relationship in which the algae supply the worm with carbohydrates and fats and the worm supplies the algae with nitrogen waste products and a safe haven.
How do triclads reproduce?
Many of the triclads divide by transverse fission: the body splits transversely behind the pharynx and each part generates the rest of the body. The posterior portion attaches to the substrate and the anterior portion crawls away until it tears in two. In species such as Dugesia, the cells tend to vary in their ability to regenerate. The cells in the middle portion of the body have the strongest ability to regenerate. Experiments have shown that if just the tail is cut off, it will not grow a new body, whereas the main portion of the body will regenerate a new tail. The ability of the fissioned portions of these worms to regenerate the proper half has interested scientists for years in investigating why the head portion grows a tail and why the tail portion regenerates a new head. In the genera Catenula, Microstomum, and Stenostomum (orders Catenulida and Macrostomida), multiple transverse planes develop that lead to a train of individuals called zooids that do not detach until they reach a certain stage. Other species (e.g., Phagocata and some terrestrial species) detach fragments that become encysted and eventually develop into new individuals.
How big is the lanceolate?
Body lanceolate or oval shaped, lateral margins undulated, measure 0.6 × 0.2 in (15 × 4 mm) ranging up to 0.9 in (25 mm). Caudal adhesive disk wide as body and set off from the rest of the body; pharynx large about one-third of body; eye lenses absent; numerous testes distributed throughout body; whitish in color.
What are the species that live in submerged substrates?
Many of the minute species occur interstitially between grains of sand in aquatic habitats. Larger species are pelagic (marine) or live among submerged substrates such as rocks, coral, and algae. Many species, especially of the order Rhabodocoela, are symbiotic with various invertebrates and fishes. A few genera of the order Tricladida are terrestrial, living in damp leaf litter and soil.
What is the body shape of a discoid?
Body is oval or discoid with retractile nuchal tentacles ; marginal eyes in band, cerebral and tentacular eyes present; pharynx long in middle of body, intestinal branches not anastomosing; male and female gonopores close to each other in posterior of body.
How does a planarian capture earthworms?
It captures earthworms by attaching ventral side of head and tail. Thrashing by prey results in planarian getting a better grasp on prey. Arthropods and mollusks are not preferred foods; slugs were only eaten if they were torn open first.
How big are worms?
Elongate worm 0.7 in long by 0.4 in wide (18 mm long by 11 mm wide ); may get larger. Two slightly developed nuchal tentacles. Body is deep red with white flecks or dots centrally located; yellowish band around the margin with deeper shades of purple between margin and central area with flecks. This genus is speciose on coral reefs and colors vary considerably between species ranging from bright pink and orange to blue and green.
Evolution and Systematics
Physical Characteristics
- The class Turbellaria share the following characteristics with other classes within the Platyhelminthes: 1. triblobastic (three tissue layers) 2. acoelomate (no fluid filled body cavity or coelom) 3. bilaterally symmetrical 4. dorsoventrally flattened 5. spiral cleavage and mesoderm derived from the 4d cell 6. complex, incomplete gut (no anus) 7. c...
Distribution
- Turbellarian species are distributed worldwide, mostly in freshwater and marine environments with a few taxa occurring on land.
Habitat
- Many of the minute species occur interstitially between grains of sand in aquatic habitats. Larger species are pelagic (marine) or live among submerged substrates such as rocks, coral, and algae. Many species, especially of the order Rhabodocoela, are symbiotic with various invertebrates and fishes. A few genera of the order Tricladida are terrestrial, living in damp leaf litter and soil.
Behavior
- Turbellarians display a number of behaviors that prevent them from straying beyond their normal habitats and allows to them to maintain orientation within those habitats. For instance, most turbellarians are positively thigmotactic (touch) ventrally and negatively thigmotactic dorsally. This allows them to maintain their ventral side against the substrate in benthic forms. In other s…
Feeding Ecology and Diet
- Most turbellarians are carnivorous predators or scavengers. Carnivores feed on organisms that they can fit into their mouths, such as protozoans, copepods, small worms, and minute mollusks. Some species use mucus that may have poisonous or narcotic chemicals to slow or entangle prey. Some have specific diets and feed on sponges, ectoprocts, barnacles, and tunicates. Sever…
Reproductive Biology
- Asexual reproduction is a common method of reproduction in freshwater and terrestrial turbellarians. Many of the triclads divide by transverse fission: the body splits transversely behind the pharynx and each part generates the rest of the body. The posterior portion attaches to the substrate and the anterior portion crawls away until it tears in two. In species such as Dugesia, t…
Significance to Humans
- The regenerative abilities of Dugesiahave been studied extensively by scientists to better understand the healing and cell regeneration processes in humans. Several species parasitize commercially important species such as oysters and a few species cause pathological problems in marine ornamental fishes kept in aquaria.
Species Accounts
- No common name
Notoplana acticola - Oyster leech
Stylochus inimicus
Resources
- Books
Brusca R. C., and G. J. Brusca. Invertebrates.2nd ed. Sunderland, MA: Sinauer Associates, Inc., 2003. Cannon, L. R. G. Turbellaria of the World—A Guide to Families and Genera.Queensland, Australia: Queensland Museum, 1986. Kearn, G. C. Parasitism and the Platyhelminths. New York…