Worms take part in diversity, and they go into three major groups. Namely one of them is flatworms. Although flatworms are often known for being parasitic (because of it being the majority on its species), there are a minority species of flatworms that are known to be harmless towards humans (free-living).
Flatworms are also known as platyhelminth. They belong to the phylum Platyhelminthes, they are invertebrates, meaning they do not possess vertebral column (backbones).
Other general Characteristics of Flatworms include:
Flattened dorsoventrally, meaning its body is flat from surfaces lower and upper surfaces.
Aceolomates, meaning they do not possess a body cavity.
Triploblastic, meaning they have three primary embryonic cell layers: Ectoderm, mesoderm and endoderm, from which different tissues and organs of the animal's body differentiate out.
Show cephalization, meaning they use concentration of sensory organs at anterior or head end.
Bilateral symmetry, meaning they own body shapes that are mirror images along a midline called the sagittal plane.
Unsegmented, they do not have different segments.
Bulk of their body is occupied by mesenchyme.
Digestion and excretion of Flatworms
From the common opening: Mouth and Anus
Flame cells excrete waste to pores (Nephridiopores)
The planarians have simple bilateral systems with longitudinal nerve cords, usually three to five pairs, extend posteriorly from the brain. Connected by transverse commissures, and smaller, lateral nerves extend from the cords. The lateral nerves give rise to the peripheral nerve plexuses.
Parasitic species have less developed nervous systems.
Simultaneous hermaphrodites, has both the male and female sex organs and produces both types of gametes.
Transverse fission (asexual).
Parasitic species have multiple hosts and different larvae stages.
Planarian species have the ability to regenerate bodies and repair wounds, and can develop new worms.
Q: How planarians can be killed?
A: Planarians live in aquatic environments, so one of the methods is they can die by being dried on land, or being burnt.
Classes of Flatworms (Click to see characteristics):
Habitat: Aquatic, and land.
Examples: Polycladida, Planarians, Geoplanidae.
Roughly 1 centimetres long, oval shaped.
Habitat: Liver of goats, sheep, cows and buffaloes
External parasites with one generation life cycle
Habitat: Specific hosts of freshwater and saltwater species
Examples: Examples: Monogenetic flukes.
Parasitic species with a scolex (anchor to host) and proglottids (reproduction).
Environments of parasitic worms:
Primary Host: Adult form feeds and reproduces
Intermediate Host: Larval form feeds and reproduces
Species of concern:
Schistosomiasis: Bores into skin -> travels into circulatory system -> Causes body inflammation from trapped eggs under skin.
Chinese Liver Fluke: Lives in bile duct of cats, dogs, and humans. Causes from infection from eating raw fish.
Beef/Pork tapeworms: Causes from infection from undercooked meat/pork. Results in digestive problems and weight loss.
So what are the importance of flatworms towards the environment?:
Through their large surface compared to their volume they can exchange gases like carbon dioxide, oxygen and ammonia across bodies.
Adapts to many conditions, making them be able to adapt to a variety of habitats.
Provide food for certain animals, examples: Six-line wrasse, Spotted Mandarin, Blue Velvet Damselfish, Dragonflies (young stage).
Flatworms have important roles for ponds, lakes, and healthy streams.
They are consumers of protozoans, rotifers, zooplankton, and algae, and help to regulate populations of these organisms.