Platyhelminthes (Flatworms)
Physical Appearance
This is just a fancy way to say Flatworms, so go impress your friends. Platyhelminthes are simple, bilteral, unsegmented, soft bodied creatures by nature. This picture clearly shows off some characteristic such as their bilateral shape and how they are one mass not split into segments liek other worms. They only have an eye, a brain, one nerve, mouth which is also to release waste, and intestine. The cilia is the only form of muscle that can be found in a flatworm.
Platyminthes are split into into three classes two of which have two subclasses.
Turbellaria
There are about 4,500 species of turbellaria which are usually very small (1mm to 600mm). They mostly live in dark, humid places (underwater caves) and are nocturnal predators and scavengers. Some of them can be parasites and some symbiotes to crustaceans.
They do not have a cuticle, but some of them have a syncitium which is a collection of cells with multiple nuclei and a single shared external membrane. Turbellaria usually have one pair of oceli, which are just little eyes, but some can have at least two or three pairs or maybe even clusters around the brain.
They do not have a cuticle, but some of them have a syncitium which is a collection of cells with multiple nuclei and a single shared external membrane. Turbellaria usually have one pair of oceli, which are just little eyes, but some can have at least two or three pairs or maybe even clusters around the brain.
Here is a turbellaria in its natural habitat, the underwater cave |
Trematoda
More commonly known as fluke worms, these
platyhelminthes are parasitic by nature. They attach to their host using suckers or anchors. This class is made out of two parasitic subclasses: The Digenea and the Aspidogastrea.
Digenea
This is the biggest subclass, which makes the tremotoda the biggest class, because it has over 11,000 species discovered which is more than all the other platyhelmenthis combined. Most of them have complicated life cycles with up to seven stages which differ on what their current enviroment is. Adult tremotoda usually have two rings around the mouth and a larger sucker in the middle of what would be the bottom in a free-living flatworm. The size of adults is usually about 0.2 mm (0.0079 in) and 6 mm (0.24 in) in length. Being parasites they live off of other organism's by going into the intestine, lungs, large blood vessels, and liver.
Aspidogastrea
This group is a lot smaller than the Digenea. They have either a single divided sucker or a row of suckers that cover their underside. They mostly take fish and turtles as their hosts, but sometimes go into freshwater bivalves, and gastropods body cavities. In their usual life cycle they take on or two hosts.
Cercomeromorpha
These are parasites that use disks that have crescent shaped hooks to attach themselves to their hosts. They consists of the subclasses: Monogea and Cestoda.
Monogenea
Most of the monogeans 1,100 are external parasites that require particular host species, which most of the time is fish but can also be aquatic reptiles or amphibians. Adult monogeans have large attachment organs at the rear called haptors, which have suckers and hooks. They made their bodies flat so as to minimize water resistance to be better suited in their enviroment. Some of them can secrete enzymes to digest the host's skin, allowing them to feed on blood and cellular debris. Others graze externally on mucus and flakes of the hosts' skins. The name "Monogenea" comes from the fact that these parasites have only one nonlarval generation
Cestoda
These are more commonly known as tapeworms. They do not have mouths or guts, but absorb nutrients through their syncitial skin from the host. To infect the host it chemically disguises himself in order to bypass the immunity system. Tapeworms have a inefficient chemical process for their metabolism, so they make up for it by taking in large amount of nutrients from the host. This makes them very deadly because it infects a host and uses up the nutrients the host needs in order to survive which lowers the strength of their immunity system and makes the host more susceptible to disease.
Here are some pictures of tapeworms
Muscular System
Not much to say about platyhelminthes' muscle system. They have cilia along skin that allow them to move around and two layers of muscle under its skin for protection. The video below shows that it uses the cilia on the side to push itself in a forward direction.
Credit goes to Tuvix72 for filming this flatworm in motion.