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).
Flatworms found in freshwater habitats are called Dugesia. Dugesia is a triangular-shaped flatworm with regeneration capability.
Kingdom
- Animalia: animals
- Eumetazoa: metazoans
- Bilateria: Bilaterally symmetrical
- Protomia: Protostomes
- Platyhelminthes: flatworms
- Class: Turbellaria
- Order: Tricladida
- Family: Planariidae
- Genus: Dugesia
- Species: Dugesia agilis, Dugesia antillana, Dugesia dorotocephala, Dugesia gonocephala, Dugesia lugubris, Dugesia polychroa, and Dugesia tigrina. Flatworms are classified based on their characteristics. As a result, the common traits of dugesia distinguish the organism from other worms. Thus, Platyhelminthes are classified based on their body nomenclature. The external characteristics of each species represent its adaptive features and classification.
Anatomy
With the help of numerous investigations, Dugesia’s 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 side. 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 the 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. However, the length of the organism determines its stages of maturity. Moreover, being hermaphrodites, they have a special and unique way of reproducing. All worms have male and female genitals. However, they still reproduce meeting another individual and aligning contact.
The outer layer of Platyhelminthes has a fringe of hairlike projections in the turbellarians. However, the epidermis of other classes of Platyhelminthes has a cuticle. Flatworms have an outer and inner longitudinal layer that supports the movement. Consequently, flatworms have a pouch-like digestive cavity and a single opening for food intake and excretion. The digestive cavity of flatworms varies among different species. As a result, the nerve cords of dugesia connect the brain to the body.
The reproductive system of Platyhelminthes distinguishes them from other worms. As a result, dugesia reproduce sexually and asexually. However, cross-fertilization in flatworms is internal. Dugesia is a hermaphrodite that reproduces through cross-fertilization. Consequently, flatworms reproduce by fission. As a result, dugesia can separate and regenerate asexually. The regeneration process of flatworms takes fourteen days. However, the outer layer is differentiated by muscle fibers. The observable features of dugesia include the eyes, body wall, intestines, mouth, head, and pharynx. A survey on the regeneration capability of Platyhelminthes revealed that stem cells stimulate body growth. As a result, the severed body parts trigger the regeneration capability of flatworms.
Ecology
Dugesia does not have too many specifics. It may be found in freshwater ponds, streams, and lakes of such countries as India, Russia, the United Kingdom, the United States of America, and Myanmar (Kotpal, 2012; Pongratz, Storhas, Carranza, Michiels, 2003). Planarians are free-living flatworms that survive 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 no 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 an opportunistic predator. Its main ratio includes some parts of freshwater organisms, some other smaller worms, and maggots.
However, feeding is stopped if the temperature is low and an individual is not able to save their own temperature. Some classes of flatworms are parasitic, ectoparasites, and endoparasites. Flatworms have a complex lifestyle and ecology because they live in multiple hosts. However, the host organism could be a vertebrate or an invertebrate. The choice of the host organism depends on the ecosystem. The ecological significance of flatworms can be summarized based on human interaction and importance. As a result, they can exist in various habitats and organisms. However, flatworms serve as food concentrates for water animals. The interaction between humans and Platyhelminthes is parasitic. As a result, they are found in human digestive tracts. Consequently, flatworms improve the organic concentration of farming land. However, the symbiotic relationship of flatworms supports their existence.
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 reproducing. An individual can split into two flatworms. As a 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.
The groups of dugesia include acoels, rhabdocoels, allocoels, triclads, and polyclads. Consequently, the regeneration mechanism begins with amputation or body loss. As a result, active proteins are triggered upon amputation. The interaction between active proteins and follistatin facilitates the development of new body layers. The ability to regenerate body tissues supports the lifespan of Platyhelminthes. Respiration and nutrient transport in dugesia occur by diffusion. The nerve response mechanism in dugesia stimulates the eyespots, pits, and auricles. The eyespots respond to light while the auricles respond to touch.
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 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 the main mechanisms of their regeneration. In the course of the experiment some facts which prove the 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 organism is equal parts showed clear reaction to an external irritant. With this in mind, it is possible to underline the high level of regenerative powers between Dugesia and their ability to experience asexual multiplication. The experiment can serve as the best evidence for 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.
Research hypothesis
The hypotheses for the experiment will validate the research objectives.
- Ho = there will be no significant difference in regeneration time in varying temperatures
- H1 = that dugesia exhibits negative phototaxis upon touch and decapitation.
- H2 = that dugesia species reproduce asexually.
An alternative hypothesis states that regeneration occurs faster at room temperatures.
Methods
First, the evaluation of literary sources and previous investigations on Dugesia, its features, and the 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. The 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 as a hermaphrodite type (the asexual reproduction of the pharynx and the sexual reproduction of the brain and stem cells).
Results
The following research is devoted to the investigation of the peculiarities of flatworm Dugesia, their main anatomy, ecology, and the issue of regeneration. The data can be seen in Table 1.
Table 1
The hypothesis of the research states that the phenomenon of asexual multiplication can be observed among flatworms due to the high level of neurogeneration and regenerative abilities. The research findings revealed that Phototaxis is peculiar with both organisms. Moreover, it is possible to suggest that being almost equal in length, new individuals will be able to regrow missing parts of their bodies and develop into a mature organisms. This suggestion can be made based on the observations in Table 1. It shows the growth of individuals during the week of observations. This fact proves the great regenerative abilities of flatworms.
Discussion
Having conducted research and obtained results, it is possible to make certain conclusions. Results show that regenerative processes peculiar for flatworms are of great importance for the whole natural and scientific world. Unique regeneration processes with the cellular and molecular dissection show a great significance of the flatworm for understanding the peculiarities of regenerative processes in brain, stem cells, and pharynx. Moreover, the issue of asexual multiplication showed the ability of flatworms to regenerate the above-mentioned important parts of the body. Taking into account the fact that cells of flatworms are similar to early embryonic stem cells of higher animals, knowledge of the main mechanisms of multiplication of flatworms can give a great number of possibilities for the investigation of the same mechanisms among animals.
The results obtained in the course of experiment proved the presence of asexual multiplication among Dugesia species. The work Phylogeography of competing for sexual and parthenogenetic forms of a freshwater flatworm: patterns and explanations by Pongratz, N., Storhas, M., Carranza, and & Michiels, N. K also investigates reproduction abilities of flatworms. However, this article centers around the question of competition between species while our research investigates asexual multiplication to understand its peculiarities and use them to understand the same processes peculiar for human beings.
It should also be said that the issue of asexual multiplication is very important nowadays as it can promote further development of the understanding of regenerative processes peculiar for people. With this in mind, it is possible to suggest further investigation of this issue in order to obtain more distinct results.
The results show measurements at different days of regeneration. Measurements were documented for original length, anterior segment, and posterior segment. Consequently, the net change for anterior and posterior measurements was analyzed. The research findings revealed that the parent organism regenerated after amputation. Consequently, the regenerated parts were developed based on close observation. The length of the anterior and posterior segments regenerated equally, after 7 days of decapitation. Consequently, the organisms demonstrated a response to negative phototaxis. The original length of twelve flatworms revealed that the average regenerated measurement was 0.7 millimeters for the anterior segment. However, the average measurement for the posterior segment was 1.14 millimeters. The results revealed significant changes after decapitation. The research finding consisted of previous literature on the regeneration capability of planarians. Consequently, the research findings revealed that flatworm regeneration requires time. Previous literature suggested that other factors affect the reservation time. However, we estimated that decapitation triggers the protein sequence for regeneration.
Table 2
The results revealed that temperature affected the regeneration process. As a result, the hot temperatures slowed the regeneration process. Consequently, the concentration of the environment affected the regeneration time. Previous literature revealed that caffeine affected the regeneration process. The analysis revealed a negative response to phototaxis. As a result, the specimen measurements showed that the anterior and posterior segment was negative. The negative response was consistent with the results of previous research findings. The table below summarizes the phototaxis response of planarians. However, the regeneration process did not affect the phototaxis results. Thus, dugesia showed a negative behavioral response to light.
Table 3 shows the response of each specimen on the fourth day of regeneration. The responses to light and stimulus were consistent with previous evidence on regeneration. Consequently, each phototaxis measurement affected the regeneration process. As a result, specimens with higher phototaxis took a longer period of regeneration.
Table 3
Table 4 revealed the changes in the anterior and posterior segments of planarians. The results showed that each specimen was photophobic. As a result, the original length of the specimen was achieved on the seventh day of regeneration. However, the results revealed varying changes in measurement. The change in measurement was associated with temperature, pH, and light.
Table 4
Table 5 revealed the overall anterior and posterior measurements in the regeneration process. The results show the net change in the posterior and anterior segments of each specimen. Consequently, the average length of each regeneration period revealed a significant change. The average posterior measurement on day 7 was 4.76mm while the anterior segment was 4.843. However, the net change for the anterior and posterior segments was 0.518 and 0.346 respectively.
An evaluation of previous literature revealed that planarians evaded light during regeneration. The result was consistent with the previous analysis of regeneration. A survey carried out on planarians revealed that sample specimens responded to a different wavelength. Table 6 summarizes the photo effect of the regeneration process. The light and dark measurement of the posterior and anterior segments was consistent with previous literature.
Table 6
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.