Flatworms are exactly what they are called; they are a flat worm, very thin and look like a small leaf. They are an unsegmented flat worm with a head and a tail end. Platyhelminthes is the name known for flat worms in scientific literature. Flatworms are the simplest of the worm groups. There are about 20,000 species in this group. They are found many places and can be free living or parasitic. A parasite lives off of another living thing called a host and can be harmful. One of the best known flatworms is the tapeworm. The tapeworm can get into a person's digestive tract and grow to enormous lengths. The tapeworm then eats off the host and is dangerous to the host as it grows and consumes more of the host and its food. Flat worms are generally very thin and can be several feet long, and most of them are microscopic. A flatworm has bilateral symmetry. It gets rid of wastes through the same opening it takes in food. The reproduction is done by splitting into two, When a flatworm is split up it immediately forms a new flatworm. It does not have a formal respiratory system though it takes in oxygen (New Zealand under water Life).
Ancestral flatworms may have first appeared around 570 million years ago. Flatworms crawled forwards and so evolved sensors for smell and touch at their front end. An organ, the brain, developed at the front to process this information, with nerves going back to control the flatworm's body. The approximately 13000 species of flatworms found around the world today are divided in to five different groups such as; Flukes, Tapeworms, Planarians, Monogenea and Aspidocotylea. Most of them are being parasitic, while the Planarians are the only mostly free-living. However Aaron G. Maule and Nikki J. Marks describes about it as the Phylum Platy helminthes is comprised of an enormous diversity of species that occur in all seas, rivers and lakes and all continental land masses. With a soft body lacking any cuticle or protective covering, the majority of species are found in moist or aquatic environment.
One very important is that they have no body cavity other than their gut. They also do not have an anus, and therefore the same opening is used to takes in food and expels waste.
The respiratory system and blood system on flatworms are also completely missing and therefore, diffusion (penetrate through pores) is used for transport of oxygen inside the body. This is one reason why flatworms are flat.
These worms are fairly common through out New Zealand, and the rest of the world. They live on the bottom in shallow water. Sometimes the darkish colored ones are found around rock pools and sometimes the brightly colored ones are found in slightly deeper water.
Flatworms are generally plain bland colors though some found have bright colored stripes or markings on them making them quite unique. Their brilliant color patterns much like nudibranches have evolved entirely for defense against predators, mainly fish.
Like with many other colorful animals e.g.: some frogs, this bright coloration is often associated with the presence of a distasteful toxic or poisonous defense substances that warn potential predators that the flatworm is full of distasteful chemicals and not worth attempting to eat. . Therefore, it can be assumed that conspicuous colors are mostly associated with the presence of toxic and bad tasting compounds.
The different colures of the flatworms can be extremely fabulous. In quite a remarkable evolutionary convergence these animal groups have evolved bright color patterns and similar chemical defense strategies. The polyclad family Pseudocerotidae includes some of the most conspicuously colored and extraordinarily diverse marine flatworms. They have been found throughout tropical and subtropical waters and are prominent members of coral reef communities (Marcela and Quiroga 2007). Unlike many multicellular animals, the bodies of this organism are not always tightly integrated into a single functional unit. Many of these animals are sessile as adults, but have free-swimming larvae (or other life history stages) that aid in dispersal to new, suitable substrates for settlement, metamorphosis and growth into adult forms. They have no obvious sensory structures, and their digestive system is highly reduced, secondly, much of their internal structure is devoted to reproduction. For a parasite, maximizing its likelihood of transmission to a new host is a priority. Being aware of its environment is not very important, because it does not need to search for food or be aware of potential predators. In addition, parasites absorb nutrients from their hosts, thereby reducing the need for a digestive system. Evolution has resulted in a significant reduction in the complexity of the sensory structures and digestive systems of flukes compared to the presumed common ancestor of flukes and free-living flatworms (Ashford and Crewe 2003).
The brain and peripheral nerve network of free-living flatworms represent the most primitive nervous systems currently under investigation. It consists of a small but well-defined brain (right panel) and numerous peripheral motoneurones connected by longitudinal nerve cords and transverse commissures (left panel). This nervous system enables flatworms to perceive environmental changes and to respond to internal and external stimuli.
The flatworm’s brain communicates with the rest of its body through six longitudinal nerves. If the brain is removed, flipped 180 degrees in any direction, and reinserted, the flatworm is not only able to regenerate connections to the brain, but the brain is able to adapt and restore almost full functionality to the flatworm. This remarkable adaptability stands in stark contrast to, say, a modern microchip. Not only would the chip not function if plugged in backwards, but it also would most likely be destroyed. Understanding and recreating this remarkable robustness is the primary goal of the Synthetic Brains project (Bryan Adams 2004).
A great deal remains to be done before the biodiversity of the invertebrates is even partially known. Yet invertebrates are extremely important in forming the basis of many food chains and as drivers of natural processes; termite and millipede communities, for instance, each consume the same or more plant biomass than large (admittedly more charismatic) mammals. Perhaps it is time to pay greater attention to invertebrate biodiversity.