Platyhelminthes is a term that covers some thirty four thousand species of flat worm. The following gives a brief outline of the Platyhelminthes characteristics shared by these creatures.
The word Platyhelminthes comes from the Greeks words “platy” meaning flat and “helmins” meaning worm. The word covers a whole range of flat worm species, all of which share major Platyhelminthes characteristics. Their soft flat, ribbon like bodies, are not segmented, have no circulatory or respiratory organs; they have membranes that enables them to absorb nutriments and oxygen by diffusion.
Other Platyhelminthes characteristics shared by these creatures is they are bilaterally symmetrical, this means the left and right sides of their bodies are mirror images of each other. They have distinctive head and tail ends and their body contains three cell layers. The outer, middle and inner layers, with the inner layer made up of spongy cells. It is a Platyhelminthes characteristic that because of this spongy cell matter in their middle layer, they have no inner body cavity.
As respiration happens through the body surfaces of these animals, they are liable to suffer a loss of fluids and experience severe dehydration. The result of these typical Platyhelminthes characteristics is to restrict their environment to wet or moist surroundings. Some species live in sea or fresh water, while others live terrestrially in among moist grains between soil, in leaf mould or in the bodies of insects as parasites.
Having the amazing ability to regenerate their body tissues is another of the Platyhelminthes characteristics. This enables them to reproduce both sexually and a-sexually. By attaching the mid region of their bodies to a substrate that induces a constriction, the creature is divided into two separate animals. These two new individuals are usually hermaphrodites, possessing both male and female sexual organs.
The thirty four thousand species in the Platyhelminthes group have been categorized under four classes.
Turbellaria are free living flat worms.
Monogea are ectoparasitic: parasites that attach themselves externally to their host’s body.
Trematoda include the common fluke, and are mainly internal parasites.
Cestoda are also internal parasites and are commonly known as Tapeworms.
The Platyhelminthes characteristics are common to all four.
A small number of these species, both terrestrial and marine free living, are considered attractive to mankind. But the main Platyhelminthes characteristics are that most humans find them ugly.