The
phylum Platyhelminthes is made up of the classes Turbellaria, Trematoda
and Cestoidea. Only marine flatworms of the class Turbellaria are found
in our region and will be discussed here. The flatworms of the other two
classes are parasites to certain vertebrate species. Tubellarian worms
have a flattened, unsegmented body that lacks blood and a circulatory
system. The muscular, excretory, nervous and reproductive systems are
well-defined and are contained in the cellular layer of tissue called
the parenchyma. They have a complex reproductive system. There is a pair
of eyespots, a pair of tiny tentacles and sensory structures used for
smell and taste at the head region of the body. Due to the flatness of
the body, all of the cells are close to the body surface allowing oxygen
and carbon dioxide to be easily exchanged with the environment. The body
surface is covered with cilia which enables the worm to glide over surfaces.
They have a branched digestive system with the mouth being the only opening,
where food is brought in and waste is discharged. Tubellarian worms are
primarily carnivorous, preying upon crustaceans and other small animals,
but they may also be herbivorous, feeding on diatoms. They are also known
to scavenge on dead animal matter.
The
phylum Platyhelminthes is made up of the classes Turbellaria, Trematoda
and Cestoidea. Only marine flatworms of the class Turbellaria are found
in our region and will be discussed here. The flatworms of the other two
classes are parasites to certain vertebrate species. Tubellarian worms
have a flattened, unsegmented body that lacks blood and a circulatory
system. The muscular, excretory, nervous and reproductive systems are
well-defined and are contained in the cellular layer of tissue called
the parenchyma. They have a complex reproductive system. There is a pair
of eyespots, a pair of tiny tentacles and sensory structures used for
smell and taste at the head region of the body. Due to the flatness of
the body, all of the cells are close to the body surface allowing oxygen
and carbon dioxide to be easily exchanged with the environment. The body
surface is covered with cilia which enables the worm to glide over surfaces.
They have a branched digestive system with the mouth being the only opening,
where food is brought in and waste is discharged. Tubellarian worms are
primarily carnivorous, preying upon crustaceans and other small animals,
but they may also be herbivorous, feeding on diatoms. They are also known
to scavenge on dead animal matter.