A Study of Dugesia, a Planariam With Its Own Peculiar Characteristics

Phylogeny

The planarians, like Dugesia, are one of the types of non-parasitic flatworms that have been an object of numerous investigations and studies due to their phylogeny, anatomy, ecology, and even regeneration peculiarities (Ruppert, Fox, Barnes, 2004). About 70 species of Dugesia are already known (aenigma, japonica, notogaea, etc.), and its phylogeny is identified due to its diagnostic characters but not due to its apomorphies which are usually used in the analysis of other types of worms and planarians (Lazaro, Sluys, Pala, Stocchino, Baguna, Riutort, 2009). Classification of Dugesia is as follows (Lal, 2009): Phylum: Platyhelminthes; Class: Turbellaria; Order: Tricladida; Suborder: Paludieola; Family: Planariidae. There are many reasons why Dugesia may be set apart from other members of a similar group, and one of the most common issues is that this planarian makes individuals feel a trophic benefit from this group due to asexual populations, which are increased to a considerable size without loss or even replacement of individuals (Lewbart, 2011).

Anatomy

With the help of numerous investigations, Dugesia structure and functions become more or less clear (Natsuka, Hirohata, Nakakita, Sumiyoshi, Has, 2011). This worm may be of black, brown, or grey colors depending on its species. As a rule, it has a triangle-shaped head with a couple of eyes that help them to control the water current intensity. It is also characterized by a unique system of neuroscience and neurogeneration that makes them rather simple still useful for understanding (Nishimura, Kitamura, Taniguchi, Agata, 2010). Because of the flattered character of the body, Dugesia is often called a flatworm. Sensory lobes of the worm are placed at the back of the head from each sides. Moreover, they determine the triangular shape of the head of Dugesia. The body length usually is not very big and it varies between 9 mm and 15 mm. However, the size can vary within the norm as much depends on environment, individuals and ability of flatworms to regenerate and regrow lost parts of their body being damaged. Representatives of this species are usually produced from the cocoon. They are transparent and small. Moreover, they have no distinct sex as they are hermaphrodites. The main aspect which helps to determine whether an individual is mature or not is its length. Moreover, being hermaphrodites, they have special and unique way of reproducing. All worms have male and female genitals. However, they still reproduce meeting another individual and aligning contact with it.

Ecology

From the ecological point of view, Dugesia does not have too many specifics. It may be found in freshwater ponds, streams, and lakes of such countries like India, Russia, United Kingdom, the United States of America, and Myanmar (Kotpal, 2012; Pongratz, Storhas, Carranza, Michiels, 2003). It is a free-living flat worm which is very simple and can live under different conditions. Moreover, negative phototaxis is peculiar for this species and that is why Dugesia prefers to live in some benthic zones of freshwater reservoirs. Representative of this species can also be found on the rocks, especially their undersides and some other minerals. Usually, these organisms are found not deeper than 40 cm and prefer temperatures not higher than 25 C. That is why, a great number of basins with freshwater in different countries can serve as the best microhabitat for representatives of this species. Dugesia is known as opportunistic predator. Its main ration includes some parts of fresh water organisms, some other smaller worms and maggots. However, feeding is stopped if the temperature is low and an individual is not able to save its own temperature.

Regeneration

The regeneration process in Dugesia has its rules as any regeneration of planarians. Still, it differs from other forms of worms due to its hermaphroditic nature and the possibility to reproduce asexually and sexually at the same time. However, asexual multiplication is rather rare in the animal kingdom (Reuter, Kreshchenko, 2004), and the regeneration of Dugesia stem cells as well as pharynx and head has its particular role in the development of the chosen class. Besides, the regeneration process of Dugesia gives rise to a number of missing cell types (Umesono, Tasaki, Nishimura, Inoue, Agata, 2011). Moreover, due to the peculiarities of regeneration, Dugesia has one more way of its reproducing. An individual can split into two flatworms. As the result of this fission, two new worms appear. The original individual regrows its missing parts. Such a high level of regenerative abilities is of the utmost interest for scientists as its understanding can allow creating some new ways of cell reduplication and better understanding of the main peculiarities of the process of regeneration among people.

Objectives and Hypothesis

The analysis of neuroscience and neurogeneration of Dugesia helps to comprehend the role of the chosen group of worms and their possible effects. The main objective of current research is to introduce Dugesia as a useful organism with its own place in the natural world. Various Dugesia species have their own peculiarities, still, their common regeneration process with the cellular and molecular dissection may considerably improve the understanding of the dynamics of the regeneration process that takes place in the brain, stem cells, and pharynx. Moreover, some important characteristics of Dugesia can be taken into account by researchers in order to understand better peculiarities of existing of the organisms of this sort and try to reproduce main mechanisms of their regeneration. In the course of experiment some facts which prove great regenerative abilities of the chosen group of worms were discovered. Reaction to the light served as the main factor to determine the presence of reaction. The whole organism and than its almost equal parts showed clear reaction to external irritant. With this in mind, it is possible to underline high level of regenerative powers among Dugesia and their ability to experience asexual multiplication. The experiment can serve as the best evidence to the following hypothesis. It is possible to suggest that the rare phenomenon of asexual multiplication can be observed among Dugesia. It becomes possible due to the high level of neurogeneration and powerful regenerative abilities peculiar for Dugesia, The given hypothesis is analyzed and proved with the help of the experiment.

Methods

First, the evaluation of literary sources and previous investigations on Dugesia, its features, and regeneration process is made to understand a true essence of the chosen type of worms. Second, the experiment on Dugesia asexual multiplication has been made. Reaction of new parts to light was also investigated and compared with the reaction of the original individual. The length of new individuals was measured and written down. Finally, the analysis of Dugesia structure was done in the laboratory conditions in order to identify the conditions under which Dugesia worm may be referred to a hermaphrodite type (the asexual reproduction of the pharynx and the sexual reproduction of the brain and stem cells).

Works Cited

Kotpal, R.L. 2012. Modern Text Book of Zoology: Invertebrates. Rastogi Publications, New Delhi, India.

Lal, S.S. 2009. Practical Zoology: Vol, 3. Rastogi Publications, New Delhi, India.

Lazaro, E.M., Sluys, R., Pala, M., Stocchino, G.A., Baguna, J., Riutort, M. 2009. Molecular barcoding and phylogeography of sexual and asexual freshwater planarians of the genus Dugesia in the Western Mediterranean (Platyhelminthes, Tricladida, Dugesiidae). Molecular Phylogenetics and Ecolution 52 pp.835-845.

Lewbart, G.A. 2011. Invertebrate Medicine. John Wiley & Sons, West Sussex, UK.

Natsuka, S., Hirohata, Y., Nakakita, S., Sumiyoshi, W., Has, S. 2011. Structural analysis of N-glycans of the planarian Dugesia japonica. The FEBS Journal 278(3) pp. 452-460.

Nishimura, K., Kitamura, Y., Taniguchi, T., Agata, K. 2010. Analysis of motor function modulated by cholinergic neurons in planarian Dugesia Japonica. Neuroscience 168 pp.18-30.

Pongratz, N., Storhas, M., Carranza, S., Michiels, N.K. 2003. Phylogeography of competing sexual and parthenogenetic forms of a freshwater flatworm: patterns and explanations. BMC Evolutionary Biology 3(23) pp. 323-15.

Reuter, M., Kreshchenko, N. 2004. Flatworm asexual multiplication implicates stem cells and regeneration. Canadian Journal of Zoology 82(2) pp. 334-356.

Ruppert, E.E., Fox, R.S., Barnes, R.B. 2004. Invertebrate Zoology: A Functional Evolutionary Approach. Brooks Cole/Thomson, Belmont, CA.

Umesono, Y., Tasaki, J., Nishimura, K., Inoue, T., Agata, K. 2011. Regeneration in an evolutionary primitive brain – the planarian Dugesia japonica model. Eropean Journal of Neuroscience 34 pp. 863-869.