(Flatworms)
Polyclad flatworm, from Halstead, 1965.
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Phylum Platyhelminthes (Flatworms) Polyclad flatworm, from Halstead, 1965. |
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The phylum Platyhelminthes
(flatworms
) includes four classes, the
Trematoda
and Monogenea
(both commonly called flukes
), the Cestoda
(tapeworms
), and the
Turbellaria
. The first three classes are
parasitic
, and are often found as parasites
of various marine organisms (as well as many freshwater and terrestrial organisms).
There are
approximately 4,500 species of Turbellarians
, about 9,000 species of flukes
, and 5,000 species
of Cestodes
.
The Turbellaria are free-living flatworms , and can frequently be found under rocks or in seaweed in the intertidal and shallow water zones. A few species are pelagic , and many of the smaller forms live within sand and mud substrates. They range in size from meiofaunal forms to individuals over 60 cm. long (the largest tend to be terrestrial forms), however, most species are only about a centimeter in length. Some species are brightly colored, others tend to be a drab brown or similarly muted color. Usually carnivorous , a wide range of living and dead organisms (including protozoa , small crustaceans , annelids , molluscs , and even barnacles and oysters ) are preyed upon by various species of Turbellarians . Some species feed on algae (especially diatoms ), either as adults or when young. |
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Three of the 12 orders of the class Turbellaria:
A. order Rhabdocoela B. order Polycladida C. order Tricladida |
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References: Barnes, 1980 Barnes, Calow, and Olive, 1993 Brusca & Brusca, 1990 Halstead, 1965 Meglitsch & Schram, 1991 |
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