Flatworms (Phylum Platyhelminthes)

The 75th plate from Ernst Haeckel' s Kunstformen der Natur (1904), depicting organisms classified as Platodes

Bedford's Flatworm (Pseudobiceros bedfordi)
An example of a marine flatworm

Scientific Taxonomy and Classification

Kingdom: Animalia
Sub- Kingdom: Eumetazoa
Superphylum: Platyzoa
Phylum: Platyhelminthes

Classes that make up Phylum Platyhemlminthes:

Class Turbellaria (Flatworms and Turbellarians)
Class Monogenea (Parasitic Flukes)
Class Trematoda (Parasitic Flukes)
Class Cestoda(Tapeworms)

Orders from the Class Turbellaria:

• Catenulida
• Macrostomida
• Licithoepitheliata
• Rhabdocoela
• Prolecithophora
• Proseriata
• Tricladida
• Polycladida
  

There are about 20,000 to 25,000 species of Phylum Platyhelminthes, making these creatures widespread and extant across the world. This fact also makes flatworms the largest phylum of acoelomates.

Habitat of Flatworms
Flatworms are primarily in freshwater, marine, and damp terrestrial environments. Marine flatworms of the Turbellaria class, referred to as Polycladida, subsist in the littoral and sublittoral areas of the sea, becoming common amongst tropical corral reefs. Only a few species of Polycladida dwell in freshwater areas such as rivers, ponds, and lakes. Many Polyclad flatworms are to dominantly be found in large and immense salt water bodies of water such as the Red Sea, Mediterranean Sea, Indo-Pacific Ocean, and Atlantic Ocean. Parasite flatworms of the other Monogenea, Trematoda, and Cestoda flatworm classes populate the digestive or gastrointestinal tract of vertebrates when they have fully matured. As they develop through their juvenile years, parasite flatworms abide in the bodies of various animals.Humans may contract these parasites by eating the carcasses of parasite infested animals.

The Prey of Flatworms
As an free-living organisms, Polyclad( Marine) flat worms are often joined in the common enterprise of other invertebrates such as sponges, corals, bivalve mollusks and other sea creatures without a backbone. Therefore, Polyclad flatworms may use the other mentioned vertebrates as a source of food. As voracious carnivorous predators, Polyclads use eversible mouth parts referred as pharynx to attack and digest prey. Oysters are often a favorite meal amongst the Polyclad flatworm, who also hunt ea squirts, bryozoans, small worms, crustaceans, or snails. Some Polyclads are even cannibalistic to one another. Parasite flatworms will automatically absorb and consume the food predigested by their host, human or animal.

The Predators of Flatworms

Having a high amount of toxicity and a very bad taste, marine flatworms are highly unpleasant and undesirable to many predators. However, there are some organisms that can hunt and eat these interesting creatures.
Acording to the website http://www.wetwebmedia.com/flatworms.htm , these are the feared flatworm predators:

Chelidonura varians Eliot 1903, THE Flatworm Eating Sea Slug! Tropical Indo-West Pacific. To seven cm. in length. This one off of Heron Island, Queensland, Australia.

Lysmata wurdemanni (Gibbes 1850), Peppermint Shrimp, Caribbean Cleaner Shrimp. Tropical West Atlantic. Lives singly or in groups. Gets along with all aquarium species. Commercially produced. A reclusive, sometimes misidentified species (there are other shrimp from the area that are similar) used in the fight to limit Aiptasia Anemones in aquariums.

Halichoeres chrysus Randall 1981 (1), is a fish of two "good" and one bad common name. It should be called the Golden or Canary Wrasse for its bright bold sun-yellow color, but is most often listed as the Yellow Coris Wrasse (Arggghhh!, it is not a Coris genus member of course). This is an exemplary aquarium species that is suitable for peaceful fish-only and reef systems. To a mere 4 inches or so total length. Aquarium & S. Sulawesi photos. Eastern Indian

Pseudocheilinus evanidus Jordan & Evermann 1903, the Pin-Striped or Striated Wrasse (2). I like this fish’s other common names, the Disappearing or Vanishing Wrasse for its bashfulness. To a grand size of three inches. Indo-Pacific, including Red Sea and Hawai'i. Two in the Red Sea.


Pseudocheilinus hexataenia (Bleeker 1857), the Sixline Wrasse (2). A feisty, though small (to 4") a reef tank species. Indo-Pacific, including the Red Sea in its distribution. Aquarium and Queensland, Australia images.

The Anatomy of a Flatworm

"Of the worms, the Platyhelminthes ("flat worms") are considered the prototypes, having developed such innovations as bilateral symmetry, a head, tail, and three germinal tissue layers (stinging celled animals, comb-jellies... only have two). These simple soft-bodied animals use their skin to breath through and only have one body opening, the mouth serving also as an anus."

http://www.wetwebmedia.com/flatworms.htm

A Presentation From Ms. Lousie Mead

Last Thursday on the twenty fourth of January, Dr. Louise Mead, representing the National Center for Science Education (NCSE), came forth to our classroom to discuss upon Darwin's Theory of Evolution. Informing us first about the NCSE as a nonprofit organization seeking to uphold the education of evolution in public schools, Ms. Mead then went into great detail of lecturing us the very important ideals concerning Darwin's most controversial theory. Defining evolution in the most abrupt terms as "descent with modification and common ancestry," Ms. Mead informed us that you must think of evolution as a pattern and process. The processes or mechanisms of evolution include natural selection, genetic drift, evolutionary development, and mutations. These aspects of evolution have led to the development of many different varied species in the millenniums of these aged world. Ms. Mead further in her lecture corrected the common misconception that in evolution, humans did not unnecessarily evolve from apes and chimpanzees. The human race and those other mentioned mammals shared a common ancestor and ascendant with another primate who lived many centuries ago. To prove this, Ms. Mead told us of the fact that humans possess only forty six chromosomes, gorillas and other primates have 48 chromosomes, demonstrating that humans could not have directly evolved from apes. Another subject that Ms. Mead pondered about was the approaches to understanding divergence, or the process of one species diverging over time into more than one species. To understand divergence in a species, you must examine the patterns, assess the reproductive behavior, and test for sexual variations amongst other subjects to uncover divergence in a particular group of animals. In addition to explaining the processes of evolution and genetic divergence, Ms. Mead also informed us of a special species of salamander that she discovered and observed which surprisingly had ancestors in the East Asian nations of Japan and China. Through comparative anatomy, biochemistry, and fossil records, Ms. Mead was able to determine and pinpoint the ancestors of this particular breed of Californian salamander. The observation of these species of Californian salamanders is a study of biogeography, a branch of evolutionary science which centers on how animals can be related even when in isolation from one another. Overall, Dr. Mead's presentation of the Darwinian theory of evolution was very informative and enriched my knowledge of that branch of science even more. Dr. Mead's use of pictures and charts really assisted me in stomaching the information which she bestowed upon us. I only wish to learn more from her in regards to the aspects of Darwinism and evolution.