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What Type Of Chemicals Can The Free-Living Nematode, Pangrellus Redivius, Sense In Its Environment?

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Introduction

What Type Of Chemicals Can The Free-Living Nematode, Pangrellus Redivius, Sense In Its Environment? Introduction Chemo sensation allows animals to detect food, predators, potential mates, and other key stimuli in their environments. Animals identify chemicals as attractants or repellents and modify their behaviour accordingly. Multi-cellular animals sense chemicals using specialised cells in the nervous system. Free-living Nematodes are sensitive to numerous environmental chemical stimuli, and will chemo tax to an attractive (water soluble or volatile) compound, and avoid noxious compounds. These animals will also modify their movement, egg laying, feeding, defecation, and their developments based on the detected food available. Observations can be made into their actions via the use of a low-powered microscope or by macroscopic visualizations. Results can be recorded in a table format; a conclusion can be made; and evaluated. Nematodes are the most abundant metazoan within soil, and being decomposers are important for the health of the soil community. To determine the main behavioural factors that are affected by structural heterogeneity, consider nematode movement in one experimental situation: a nematode on an agar filled Petri-dish with/without a bacterial attractant and with/without structure. The experiment is interested in the neurological basis of behaviour. A type of behaviour that has always fascinated scientists is how animals appear to know where they are going, and often times travel many times their body length to get to their goal. Materials Agar gel in Petri-dishes / Filter Paper / Free-living Nematode, Panagrellus redivius in distilled water / Chemicals: 1mM Vanillic acid (a known volatile chemo-attractant in other systems); 1mM Glucose (purified food ...read more.

Middle

Percentage of Nematodes present after 5 minutes 0 70 82 10 Table 8, Secretary Products of Panagrellus nematode worms Ratio of Panagrellus secretary products to water OBSERVATIONS 1:3 (Dish A) 2:2 (Dish A) 3:1 (Dish B) 4:0 (Dish B) Number of Nematodes present after 5 minutes 1 3 5 25 Just a normal day for the worms... Percentage of Nematodes present after 5 minutes 2 6 10 50 Table 9, Basic, Acidic and Neutral Solutions Ratio of Solutions OBSERVATIONS 1:3 Acid (Dish A) 2:2 Base (Dish A) 3:1 Acid (Dish B) 4:0 Neutral (Dish B) Number of Nematodes present after 5 minutes 12 35 10 37 Nematodes prefer neutral to alkaline conditions to acidic conditions. Percentage of Nematodes present after 5 minutes 24 70 20 74 Discussion of Results An adequate way of displaying a control is used against chemical related results. From this experiment, nematodes forage / loop in the absence of both attractants and structure, however, within structure the looping behaviour is replaced by more random movements. In the presence of attractant gradients, emanating from the bacterial source, more linear and directed movements were observed. This model considers only one of the three main factors affecting nematode movement: chemo taxis. Random movement (diffusion) and foraging strategy are noted but are not distinctly seen because of the closeness in relation to chemo taxis. In conclusion, it is found that structural heterogeneity impeded both attractant diffusion and nematode movement. Furthermore, like higher mammals, the ability to alter their foraging behaviour to random movements and again to biased linear movements will allow them to find food and avoid predators in a variety of structural environments. ...read more.

Conclusion

Animals which suddenly find themselves in an unfavourable environment (e.g. with regard to humidity, temperature, or salt concentration) may change direction by trial and error. Also, chemo-sensation allows animals to detect food, predators, potential mates, and other key stimuli in their environments. Animals identify chemicals as attractants or repellents and modify their behaviour accordingly. Multi-cellular animals sense chemicals using specialised cells in the nervous system. Free-living Beetles are sensitive to numerous environmental chemical stimuli, and will chemo tax to an attractive (water soluble or volatile) compound, and avoid noxious compounds. These animals will also modify their movement, egg-laying, feeding, defecation, and their developments based on the detected food available. Materials Petri-dishes / Filter Paper / Flour Beetles / Hot water / Ice / Plastic gloves / Broad Forceps/scissors (from dissection kit) / food source (oats) / black paper / cardboard / large plastic box / desk lamp / mobile phone (with vibrate feature). Aim Working in groups of two, and using the materials available, students must design an experiment to address what chemical the nematode senses in its environment. Each member of the group should have an active role in the design and execution of the experiment, before writing up the practical in a suitable report format. Methods Cover half a Petri-dish in black paper - sealing it around the edges to prevent light coming in. Place 5 beetles into the Petri-dish. Position a desk lamp over the Petri-dish so that light is more intense over one side of the Petri-dish. Allow five minutes for the beetles to settle. Record the results noting the beetles' reaction and, movements to a light/dark chamber. ...read more.

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