ELECTRONIC FORUM
NSF Teacher Fellows are required to use the newsgroup forum to post the introduction, 2-week report, 4-week report, 6-week report, final implmentation plans, and abstract on the newsgroup. The following are sample postings
Sample Postings & California Standards
| Podocoryne carnea is a colonial hydrozoan that lives on the backs of gastropod shells inhabited by hermit crabs. It has no predetermined life span. Morphogenesis is probably regulated by some physiological response of the colony to its environment. The growth of the colony depends on the metabolites circulating in its gastrovascular system. That fluid is pumped by its polyps which bud at a certain average distance from each other. The force pushing the fluid is the pressure imparted by each polyp over the cross-sectional area of its cylindrical stolon, which is the encrusting tissue holding the colony of polyps together. The fluid goes so far because its flow is resisted by shear forces imparted by the walls of the stolon. |
2-WEEK REPORT
| __X__ 2 week report NSF Program/Oppenheimer, P.I. YOUR NAME Zovik Menasian MENTOR’S NAME Dr. Steve Dudgeon Summarize your work, so far, as follows. PLEASE TYPE. HYPOTHESIS YOU WILL BE OR ARE TESTING: My hypothesis is that as I increase the dynamic viscosity of the sea water in which the hydrozoan Podocoryne carnea is growing, the distance from the existing polyps to the newly growing buds will decrease and/or the number of polyps per length of stolon will increase. MATERIALS AND METHODS YOU WILL BE OR ARE USING: The materials I have used so far are:  dissecting stereomicroscope  microscope slides and coverslips  scalpels and blades (#10 & 15)  a thin brush  a culture of Podocoryne carnea  an aquarium tank  sea water  brine shrimp eggs  air pump  beakers  glass Petri dishes  test tube racks  calculator I made clonal replicates of the hydrozoan by explanting segments of the original culture on slides to which coverslips were attached with a thread. Each segment contained 3-5 polyps and a part of a stolon to ensure attachment and growth of new stolons and polyps on the coverslip. Every day I cleaned the slides with a tiny brush, fed the colonies brine shrimp hatched in sea water, and changed their water. After 10 days, they were ready to be used for the experiment. Next, I will isolate single-polyp, single-stolon systems to experiment on. They will be put into different concentrations of Dextran containing sea water to see the effect of viscosity change on the polyp to polyp distances. RESULTS, SO FAR: So far, my explanted colonies have grown successfully. For the control, I have measured the distances from existing polyps to newly forming buds. The average distance for 30 samples is 2.4  0.7 mm. WHAT ARE YOUR PLANS FOR CLASSROOM IMPLEMENTATION: One application possibility that I am planning is to use this experiment as I am teaching the scientific method to my advanced seventh grade life science class. After providing them with some background information about the organisms and their environment, I would provide the students with similar cultures and ask them to come up with questions that they may want to find out more about. After giving them some time to observe the organisms and follow their daily routines, I might suggest this experiment or the one my colleague, Bernice Krieger, is working on. I will simplify the procedure a little, since they are too young to manipulate the instrument successfully. Bernice and I plan to put our combined results on the web and gather as much data as possible about the experiment. The results could be published in the Student Research Abstracts Journal. This experiment might suggest a few other options for interested students or groups of students who might want to take it up as their science fair project for the school, county and state science fairs. PLEASE PROVIDE ANY COMMENTS ABOUT THE PROGRAM, SO FAR, AND ANY SUGGESTIONS THAT WOULD IMPROVE YOUR SUMMER RESEARCH EXPERIENCE: I have enjoyed my experience in this lab so far. It has provided me with a lot of information (theoretical and practical) for my own knowledge and has given me the tools and the opportunity to take a lot to my classroom. The presentations by the participants on August 3rd were very informative and let everyone know what everyone else was working on. There were so many ideas for classroom implementation, some simple and others more complex, geared towards all classes and abilities in a secondary school. I hope this program would continue throughout the year and for coming summers also. |
4-WEEK REPORT
| __X__ 4 week report NSF Program/Oppenheimer, P.I. YOUR NAME Zovik Menasian MENTOR’S NAME Dr. Steve Dudgeon HYPOTHESIS YOU WILL BE OR ARE TESTING: My hypothesis is that as I increase the dynamic viscosity of the sea water in which the hydrozoan Podocoryne carnea is growing, the distance from the existing polyps to the newly growing buds will decrease and/or the number of polyps per length of stolon will increase. MATERIALS AND METHODS YOU WILL BE OR ARE USING: After growing colonies of Podocoryne carnea on coverslips (placed in custom-made racks immersed in sea water), I surgically isolated single-polyp-single-stolon units that were about 2.7 mm long. These units had to be far enough from each other to reduce the chances of them fusing together during the experiment. Furthermore, the units should not contain any branches, which need to be surgically removed if present. I cleared the coverslip from the rest of the colony, which I later explanted on new slides threaded with coverslips. To increase the viscosity of sea water, I used a high molecular weight carbohydrate called Dextran. To get three different viscosities, I made solutions of Dextran with a concentration of 0.8%, 1.5%, and 2.2%. My mentor and I were concerned about the relationship between concentration of Dextran in the sea water and the change that it will cause in viscosity. Our guess was that it is a linear relationship, i.e., as concentration of Dextran increases so does viscosity with the same proportionality. To make 0.8% solution of Dextran in sea water (corresponding to a viscosity of 1.4 centipoises), I dissolved 2 grams of Dextran into 250 mL of the pasteurized sea water. To make a 1.5% of Dextran (viscosity of 1.8 cp), I added 3.75 grams of Dextran into 250 mL of sea water. To make 2.2% solution of Dextran (viscosity of 2.2 cp), 5.5 grams of Dextran were mixed with 250 mL of sea water. Unmanipulated sea water has a viscosity of 1.0 cp. Experiments suggest that at viscosities greater than 2.2 cp colonies are stressed and don’t grow well. I pasteurized sea water in order to reduce the chances of microorganisms growing once the colonies were put in tiny culture tubes. For pasteurization, I heated sea water to a temperature of 90 degrees Celsius, covered it, and let it cool before using for the experiment. To measure the viscosity of each experimental solution and the control, I used a viscometer by Gilmont Instruments. It is a cylindrical tube with the bottom closed and has a set of caps to adjust the pressure in the tube. I insert a glass ball into the tube after filling it with the appropriate liquid and I seal the top of the tube. (All liquids put in this instrument need to be vacuum filtered in order to prevent the presence of particulate matter which would interfere with the measurement.) The ball is allowed to move down the column of liquid. When the ball reaches a certain assigned level, I start timing. When the ball reaches a second set of lines, I stop timing. I calculate viscosity with the following formula:  = K (f - )t where,  is the viscosity of the liquid in centipoises (cp) f is the density of the glass ball = 2.53 g/mL  is the density of the liquid in g/mL t is the time of descent in minutes K is the viscometer constant To find K, I filled the viscometer with standard sea water and timed it. The viscosity of sea water at 20 degrees Celsius is 1.02 cp. I measured the density of sea water by weighing 1 mL of sea water. The density was 1.0095 g/mL. By rearranging the above equation, I calculated the viscometer constant, K so that: K = /(f - )t The average K value was 0.303  0.035 cp.mL/g.min. I used this value of K to find the viscosities of the 3 experimental solutions. For each one of the experimental solutions, the densities were calculated similar to that of the control. After isolating the single-polyp-single-stolon units, I cut each coverslip to a width of 1.4 cm to fit into the culture tubes assigned for them. Immersing each coverslip into its respective solution, I handfed each polyp with a single, one day old, brine shrimp. I made about 10 replicates of each unit for each of the control and the 3 experimental solutions. I filled each culture tube with about 14 mL of the appropriate solution and inserted the coverslip into it. After doing the same with all samples and solutions, I put the tubes on a machine that continuously moved the liquid in the tubes. I left the colonies this way for 3 days and changed their water once. After 3 days, I took out each coverslip and measured (with a stereomicroscope) the average distance between the polyps (original and newly grown) and the number of polyps per length of stolon. RESULTS, SO FAR: Upon measuring the viscosities of the 3 experimental liquids, I found out that the viscosity of the 0.8% Dextran solution is 1.41 cp, that of 1.5% Dextran solution is 2.07 cp and the viscosity of the 2.2% Dextran solution was 2.03 cp. These made me realize that concentration and viscosity must not be directly proportional to each other. As concentration of Dextran increases, the viscosity must reach a plateau or a constant value (at least for the values we were working with). The results of the first trial of the experiment are summarized in the table below: SAMPLE Avg. dist. bet. polyps #of pol/length of stln. Control 1.60  0.20mm 0.66  0.15/mm 0.8% Dextran solution 1.12  0.34mm 0.79  0.33/mm 1.5% Dextran solution 1.48  0.42mm 0.60  0.14/mm 2.2% Dextran solution 1.18  0.22mm 0.76  0.23/mm My results, so far, show a decrease in the average distance between polyps for the comparison among the control solution, 1.5% Dextran solution and the 2.2 % Dextran solution. However, the 0.8% Dextran solution results do not seem to follow the expected trend. On the other hand, the results for the number of polyps per unit length of stolon seem to be fluctuating. There is an increase in the number of polyps between the control and the 0.8% Dextran solution and also between the 1.5% Dextran solution and the 2.2% Dextran solution but the results are not consistently increasing or decreasing. I observed the presence of white fuzzy material covering the coverslips put into the Dextran solutions and the higher the concentration of Dextran the greater the fuzziness. Also, the polyps did not seem to be very comfortable in those solutions; they hadn’t grown much and some didn’t even want to eat. After discussing the results with my mentor, I can suggest a few reasons for this outcome: a) Since the organisms are confined to a small amount of space and water for a period of 3 days, there might be some microorganisms growing in their environment, taking away from their nutrition and adding waste to the surrounding. b) These tubes are sealed and no air circulates in them (except for a few milliliters of empty space left) unless they are taken out to change their water. Also, the more Dextran there is in the solution, the less dissolved oxygen provided to the organisms. c) The white fuzzy stuff may be the Dextran precipitating around the metabolic wastes given out by the hydroids since Dextran makes the solution very viscous and is very difficult to dissolve in sea water. WHAT ARE YOUR PLANS FOR CLASSROOM IMPLEMENTATION: In addition to what I mentioned in my previous report, some variables that my students can work on (either as their group science project idea or as part of the lab) could include: a) the effects of temperature on growth of colonies b) the influence of pollutants found in water (organic and inorganic) on the growth of polyps c) the effects of changes in salinity of sea water on growth of polyps d) checking the above variables for branching of stolons e) manipulations on the polyps (removing the hypostome, removing the whole polyp, etc.) to check for the presence or absence of head inhibitors (as my lab colleague Bernice Krieger was working on) PLEASE PROVIDE ANY COMMENTS ABOUT THE PROGRAM, SO FAR, AND ANY SUGGESTIONS THAT WOULD IMPROVE YOUR SUMMER RESEARCH EXPERIENCE: We are very fortunate to be able to work in labs where we have access to very sophisticated equipment. Unfortunately, we have to do with very little when it comes to our school and our students. I was wondering if it would be possible to have a loan or check out system where we could borrow some of the equipment from the university for our classrooms. One of the things that I would need for my classroom implementation plans would be stereoscopic dissection microscopes which we have none at our school. Hopefully, the principle will be convinced to buy at least one and the students can view the manipulations or surgical procedures performed by one person on a TV or computer monitor. |
6-WEEK FINAL RESEARCH REPORT
| 6-WEEK FINAL RESEARCH REPORT NSF Program/Oppenheimer, P.I. YOUR NAME Zovik Menasian MENTOR’S NAME Dr. Steve Dudgeon TITLE OF YOUR PROJECT: The Effects of Viscosity on the Growth Patterns of the Hydrozoan Podocoryne carnea ABSTRACT: Podocoryne carnea are colonial hydrozoans that live on the backs of gastropod shells inhabited by hermit crabs. They get their energy through their polyps which act as pumps to move the nutrition into their gastrovascular system in the stolon. It is speculated that the cells lining the walls of the stolon can sense pressure differences and, when necessary, can differentiate to form polyp buds. My hypothesis was that as the viscosity of the sea water in which these hydroids are living is increased, new buds will form at a closer distance from an existing polyp than they would in their ordinary sea water environment and/or the number of polyps per length of stolon should increase. To do this, single-polyp-single-stolon units of the Podocoryne carnea colony growing on coverslips were surgically isolated and put in small conical tubes containing sea water mixed with either of 3 different concentrations of Dextran, a high molecular weight carbohydrate that increases the viscosity of the sea water with no significant change in density or osmolarity. The colonies were kept in these tubes for 3 days. Each polyp was individually fed with one brine shrimp nauplius every day and the water changed. After 2 trials, the results were not very consistent. The average distance between polyps did decrease overall (after combining the results from 2 trials) but the number of polyps per length of stolon decreased at lower concentrations of Dextran but increased at the higher concentrations. My hypothesis was not proven completely to be true. There might be some other factors involved in the emergence of this trend. INTRODUCTION: Podocoryne carnea is a sessile marine hydroid consisting of feeding polyps connected by stolons, which form a common gastrovascular system (Blackstone and Buss 1992). This irregular stolon system is adherent to a substrate which, in this case, is the gastropod shell inhabited by hermit crabs (Braverman 1971). Podocoryne, like all colonial organisms, asexually propagates individuals of the same genotype by maintaining a mitotically active stem cell lineage. Like many colonial organisms, there is no predetermined size or life span and no known senescence. Moreover, the size and shape of the substrate it lives on varies with individual shell. Gastrovascular fluid circulates in the lumen of the stolons and carries food and other metabolites throughout the colony (Blackstone and Buss 1992). The polyp is the only component of this system that can exchange fluid between the external medium and the rest of the gastrovascular system (Dudgeon et al. 1999). Contractions of the muscular polyp propel the gastrovascular fluid. Flow is in either direction in the stolon but not simultaneously (Dudgeon and Buss 1996). This fluid transport system in hydrozoans is the only physiological system that is manifested colonywide. The growth of the colony results from three types of changes: a) elongation of stolons at their tips, b) branching of stolons, and, c) formation of new polyps on the stolons (Braverman 1971). In this way, a colony covers the available substratum with a loose network of encrusting tissue. As it reaches the limits of the substratum, there is enhanced polyp and stolon tip formation which creates a dense interconnected network and will soon initiate the formation of the sexual medusoid stage (Blackstone and Buss 1992). In Podocoryne, the number of polyps per unit stolon length is roughly constant for a given clone. The probable reason for this is that at some distance from a polyp another polyp is needed to continue the transport of fluid to the growing tips of stolons. The force pushing the fluid is the pressure imparted by the polyp over the cross-sectional area inside the stolon. The fluid is only going to go so far before the force imparted by the push of the polyp is balanced by the shear forces acting along the walls of the stolon as represented by the following equation: Fp = p (r2) =  du (2rl) = Fr dr where Fp = force imparted by the polyp p = pressure drop per unit length of stolon r2 = cross-sectional area of stolon  du/dr = shear viscous forces 2rl = surface area inside of the cylinder (stolon) Fr = force resisting the push Shear stress is the force exerted by a fluid moving over a surface. It is the product of dynamic viscosity and the velocity gradient across the stolon radius. Shearing of a fluid indicates the sliding of a large number of very thin sheets across one another. Dynamic viscosity, then, is the stickiness or friction between these sheets (Vogel 1981). Endothelial cells along the stolon lumen are sensitive to this shear stress (in mammalian vascular systems at least) and at some low threshold shear stress which reflects a low velocity of fluid transport, those cells may differentiate to form a polyp bud. Previous experiments have shown that application of 2,4-dinitrophenol (an uncoupler of oxidative phosphorylation) reduces the energy available for polyps to pump gastrovascular fluid. This could also be accomplished by overfeeding which increases the solute concentration and, as a result, increases dynamic viscosity (Dudgeon and Buss 1996). MATERIALS AND METHODS: All colonies of Podocoryne carnea were asexually propagated from a single clone. Colonies were grown on the surface of coverslips (484 mm2) attached to slides in an aquarium containing artificial seawater with aeration. Animals were fed every day on a diet of 48-hour-old brine shrimp nauplii and returned to the aquarium after uningested shrimp had been removed. Aquarium water was replaced with fresh seawater daily. Colonies were propagated asexually by surgically explanting 3-5 polyp systems attached to stolons onto the surface of a coverslip. All surgical procedures were carried out under a Wild Heerbrugg dissecting stereomicroscope. Explanted polyps were held in place by a loop of thread until the growth of stolons attached them to the surface, whereupon threads were removed and coverslips separated from slides. Coverslips were suspended in floating racks in seawater with aeration. Single-polyp-single-stolon units were surgically isolated by severing all stolons connecting the chosen polyp to the colony so as to retain a segment of stolon about 2.7mm long with two blind ends with the polyp positioned near the center. Severed stolons heal instantly. A number of similar units were isolated on the same coverslip, making sure the units were far enough from each other to avoid connecting of stolons or overlapping of units as they grew during the experiment. All branches were also removed from the unit. To increase the viscosity of seawater, a high molecular weight carbohydrate called Dextran (high fraction) was used. To get three different viscosities, solutions of Dextran with a concentration of 0.8%, 1.5%, and 2.2% were prepared. My mentor and I were concerned about the relationship between concentration of Dextran in the seawater and the change that it will cause in viscosity. Our guess was that it is a linear relationship, i.e., as concentration of Dextran increases so does viscosity with the same proportionality. To make 0.8% solution of Dextran in seawater (presumably corresponding to a viscosity of 1.4 centipoises), 2 grams of Dextran were dissolved into 250 mL of pasteurized seawater. To make a 1.5% of Dextran (viscosity of 1.8 cp), 3.75 grams of Dextran were added into 250 mL of seawater. To make 2.2% solution of Dextran (viscosity of 2.2 cp), 5.5 grams of Dextran were mixed with 250 mL of sea water. Unmanipulated seawater has a viscosity of 1.0 cp. Experiments suggest that at viscosities greater than 2.2 cp colonies are stressed and don’t grow well. Seawater was pasteurized in order to reduce the chances of microorganisms growing once the colonies were put in tiny conical tubes. For pasteurization, seawater was heated to a temperature of 90 degrees Celsius, covered, and left to cool before using for the experiment. To measure the viscosity of each experimental solution and the control, a viscometer by Gilmont Instruments was used. The instrument is a cylindrical tube with the bottom closed and has a set of caps to adjust the pressure in the tube. A glass ball is inserted into the tube after filling it with the appropriate liquid and the top of the tube is sealed. All liquids put in this instrument need to be vacuum filtered in order to prevent the presence of particulate matter that would interfere with the measurement. The ball is allowed to move down the column of liquid. When the ball reaches a certain assigned level, timing starts. When the ball reaches a second set of lines, timing stops. The viscosity of each solution is calculated with the following formula:  = K (f - )t where,  is the viscosity of the liquid in centipoises (cp) f is the density of the glass ball = 2.53 g/mL  is the density of the liquid in g/mL t is the time of descent in minutes K is the viscometer constant To find K, the viscometer is filled with standard seawater and it is timed. The viscosity of seawater at 20 degrees Celsius is 1.02 cp. The density of seawater is measured by weighing 1 mL of seawater. The density was 1.0095 g/mL. By rearranging the above equation, the viscometer constant, K was calculated so that: K = /(f - )t The average K value was 0.303  0.035 cp.mL/g.min. This value of K was used to find the viscosities of the 3 experimental solutions. For each one of the experimental solutions, the densities were calculated similar to that of the control. After isolating the single-polyp-single-stolon units, each coverslip was cut to a width of 1.4 cm to fit into 15 mL polypropylene conical tubes appropriately labeled. Before immersing each coverslip into its respective solution, each polyp was handfed with a single, 48-hour-old, brine shrimp nauplius. About 10 replicates of each unit were made for each of the control and the 3 experimental solutions. Each conical tube was filled with about 14 mL of the appropriate solution and the coverslip inserted into it. After doing the same with all samples and solutions, the tubes were put on a LABQUAKE shaker (Barnstead/Thermolyne) that continuously moved the liquid in the tubes. The colonies were kept in this manner for 3 days. Every day, each coverslip was removed from its tube, each polyp handfed with one brine shrimp nauplius and tube was filled with fresh solution. After 3 days, each coverslip was removed from the tube and, using the stereomicroscope, the average distance between the polyps (original and newly grown) were measured and the number of polyps per length of stolon were recorded. RESULTS: Upon measuring the viscosities of the 3 experimental liquids with the viscometer, the viscosity of the 0.8% Dextran solution was calculated to be 1.41 centipoises (cp), that of 1.5% Dextran solution was 2.07 cp and the viscosity of the 2.2% Dextran solution was 2.03 cp. These results could indicate that concentration and viscosity must not be directly proportional to each other as I originally thought. Rather, as concentration of Dextran increases, one of 2 possible scenarios is taking place; either the viscosity is reaching a plateau or a constant value (at least for the values I was working with), i.e., maximum solubility is reached after a certain concentration of Dextran or the relationship between concentration and viscosity is not linear at all. The results from both trials are summarized in the table below. Originally, each of the control and experimental samples consisted of at least 10 single-polyp-single-stolon units. However, during the course of the experiment, some units did not survive and, as it is apparent from the data, the control units thrived while the experimental ones suffered big losses, including loss of feeding polyps, in which case the data were discarded. TRIAL 1 TRIAL 2 Sample Average distance between polyps (mm) # of polyps per mm of stolon Sample Average distance between polyps (mm) # of polyps per mm of stolon Control 1.49 0.64, 0.77 Control 1.33 0.77 1.61 1.06, 0.74 1.06 0.82, 0.72, 0.93 1.53 0.62, 0.75 0.79 0.92, 0.98 1.50 0.65 0.99 0.82 1.84 0.50 0.87 1.18 1.57 0.57 0.92 0.76 1.64 0.83 1.09 0.77 1.74 0.70 1.15 0.63, 0.71 1.96 0.52, 0.49 0.94 0.87 1.42 0.47, 0.57 0.99 0.90 1.26 0.68 0.8% Dextran Solution 0.86 1.17 0.8% Dextran Solution 1.42 0.43 0.48 1.52 1.56 0.58 0.98 0.62 1.28 0.47 1.48 0.68 1.72 0.51 0.88 0.82 1.14 0.65 1.34 0.61 1.12 0.27 1.46 0.59 1.62 0.56 1.44 0.59 1.72 0.34 1.16 0.55 1.5% Dextran Solution 1.44 0.70 1.5 % Dextran Solution 0.60 0.63 1.2 0.71 1.40 0.56 1.02 0.81, 0.49 1.32 0.57 2.12 0.56 0.78 0.80 1.60 0.56, 0.40 2.2% Dextran Solution 1.08 0.53 2.2% Dextran Solution 0.58 1.64 0.92 0.88 0.75 1.52 0.92 1.12 0.78 1.40 1.68 0.67 0.56 0.55 1.32 0.61 1.06 1.04 1.04 0.56 Below are the averages for the data from the above two trials. SAMPLE AVERAGE DISTANCE BETWEEN POLYPS NUMBER OF POLYPS PER LENGTH OF STOLON TRIAL 1 TRIAL 2 Trial 1 Trial 2 Control 1.60  0.20 mm 1.01  0.15 mm 0.66  0.15 / mm 0.84  0.14 / mm 0.8% Solution 1.12  0.34 mm 1.45  0.24 mm 0.79  0.33 / mm 0.48  0.13 / mm 1.5% Solution 1.48  0.42 mm 1.03  0.40 mm 0.60  0.14 / mm 0.64  0.11 / mm 2.2% Solution 1.18  0.32 mm 0.80  0.22 mm 0.76  0.23 / mm 1.12  0.48 / mm The results are not consistent. In trial 1, as the concentration of Dextran increases in the experimental samples, the average distance between polyps decreases, then increases, and then decreases again. In trial 2, there is a consistent decrease in average distance for the Dextran containing solutions with an original increase between the control and the least concentrated solution. The results for the second set of measurements are not consistent either. In trial 1, the number of polyps per length of stolon increases, then decreases and eventually increases again as the concentration of Dextran increases. In trial 2, however, the number decreases from control to least concentrated solution but then it increases as the concentration of the solution increases. DISCUSSION: My results are not really conclusive. Further experimentation is necessary to find out whether my hypothesis is true or not. Some changes in the procedure may be necessary to get better results. After the coverslips were taken out of the conical tubes for measurement, I observed the presence of white fuzzy substance covering the coverslips put into the Dextran solutions and the higher the concentration of Dextran the more of that white material was present. Also, the polyps did not seem to be very comfortable in those solutions; they hadn’t grown much and some didn’t even “want” to eat. After discussing the results with my mentor, I can suggest a few reasons for this outcome: a) Since the organisms are confined to a small amount of space and water for a period of 3 days, there might be some microorganisms growing in their environment, taking away from their nutrition and adding wastes to the surrounding. Research suggests that carbon dioxide may act as an inhibitor of hydranth formation (Braverman 1963). As I was opening each conical tube, especially the Dextran containing ones, a fizzing sound was heard as if a gas was escaping the tube. I do not have any way of determining the nature of that gas. b) The conical tubes were sealed preventing circulation of air in them (except for a few milliliters of empty space left) until they were taken out to change their water and for feeding. Also, the more Dextran there is in the solution, the less dissolved oxygen is available to the organisms. c) The white fuzzy matter may be the Dextran precipitating around the metabolic wastes given out by the hydroids since Dextran makes the solution very viscous and is very difficult to dissolve in sea water. Some of the colonies had lost their main feeding polyps. Although research suggests that removing the sole polyp from a young colony of the Podocoryne carnea stimulates an increase in the number of polyps later formed, the measurements from these colonies had to be discarded since it was not completely obvious to me the result that removing the sole feeding polyp would leave on the colony (Braverman 1971) In conclusion, there seems to be some kind of correlation between viscosity and growth of new polyps. For some part of the experiment, as predicted, the average distance between polyps decreases and number of polyps per length of stolon increases as the viscosity of the solution increases, i.e., as the concentration of Dextran in solution increases. However, the accumulation of flaky white precipitate on the coverslips of the experimental samples seems to interfere with the experiment. One possibility that might reduce that accumulation would be to store the coverslips in an open container, for example, on slides in a slide rack with circulating water, which will increase the amount of oxygen available to the hydroids and reduce the collection of wastes. BIBLIOGRAPHY Blackstone, Neil W, and Buss, Leo W. “Treatment with 2,4-dinitrophenol Mimics Ontogenetic and Phylogenetic Changes in a Hydractiniid Hydroid.” Evolution 89 (1992): 4057-4061 Braverman, Maxwell H. “Studies on Hydroid Differentiation – Regulation of Hydranth Formation in Podocoryne carnea.” Journal of Experimental Zoology 176 (1971): 361-381 ---. “Studies on Hydroid Differentiation, II – Colony Growth and the Initiation of Sexuality.” Journal of Embryology and Experimental Morphology 11 (1963): 239-253 Dudgeon, Steve, et al. “Dynamics of Gastrovascular Circulation in the Hydrozoan Podocoryne carnea: the One-Polyp Case.” The Biological Bulletin 196 (1999): 1-17 Dudgeon, Steven R., and Buss, Leo W. “Growing with the Flow: On the Maintenance and Malleability of Colony Form in the Hydroid Hydractinia.” The American Naturalist 147 (1996): 667-691 Vogel, Steven. Life in Moving Fluids – The Physical Biology of Flow . Boston: Willard Grant Press, 1981 CLASSROOM IMPLEMENTATION PLANS: I will introduce my research to my 7th grade advanced life science class as part of the first chapter where we study the scientific method. . After providing them with some background information about the organisms and their environment, I would provide the students with similar cultures and ask them to come up with questions that they may want to find out more about. After giving them some time to observe the organisms and follow their daily routines, I might suggest this experiment or the one my colleague, Bernice Krieger, is working on. I will simplify the procedure a little, since they are too young to manipulate the instruments successfully. Bernice and I plan to put our combined results on the web and gather as much data as possible about the experiment. The results could be published in the Student Research Abstracts Journal. This experiment might suggest a few other options for interested students or groups of students who might want to take it up as their science fair project for the school, county and state science fairs. Some variables that my students can work on (either as their group science project idea or as part of the lab) could include: a) the effects of temperature on growth of colonies b) the influence of pollutants found in water (organic and inorganic) on the growth of polyps c) the effects of changes in salinity of seawater on growth of polyps d) checking the above variables for branching of stolons e) manipulations on the polyps (removing the hypostome, removing the whole polyp, etc.) to check for the presence or absence of head inhibitors (as my lab colleague Bernice Krieger was working on) COMMENTS ABOUT THE PROGRAM: I have enjoyed my experience in Dr. Dudgeon’s lab and being a member of this summer program as well. It has provided me with a lot of information for my own knowledge and has given me the tools and the opportunity to take a lot to my classroom. I’ve also learned a lot by communicating with other teachers in the program and listening to their presentations. I hope this program would continue throughout the year and for coming summers also. |
IMPLEMENTATION MEETING REPORT
| Zovik Menasian SEPTEMBER IMPLEMENTATION MEETING REPORT PURPOSE 1. Goals:  Have students get a good grasp of the scientific method  Have students learn about a variety of cniderians that they would never get a chance to otherwise (not included in their textbook)  Prepare students for science fair experiments  Get students to brainstorm about all kinds of variables that can influence the growth of living things 2. I’ll meet my goals when:  My students are able to perform lab experiments and science fair projects with very little guidance or help from me.  My students can respond to hypothetical questions about the complexity of living organisms which should indicate the presence of critical thinking. 3. As an application of the scientific method, I would not have to cut much from the curriculum, except elaborate on the concept a little further. When studying about the phylum classification, these hydroids could be the representatives of the cnidarians, replacing details about jellyfish and corals. TARGET POPULATION 1. This project will include my 7th grade life science students as a whole classroom. Beside that I have two 9th grade students who are ready to do research on this topic and make it their science fair project, hoping to publish their abstract and take their project to the Los Angeles County Science Fair. 2. I chose my 7th grade class because they study life science at an advanced level, while the rest of the 7th graders study general science. These students have an overall science average of B+ or above and they are serious students with a lot of support from parents. I chose them because they can handle the responsibility as a class and have the preparedness for it (although their age makes it difficult to expect a lot of manipulation with sophisticated instruments). The other two 9th graders were asking me for ideas for a project and since I had had them in life science last year and know their abilities, I knew they could handle the job. CALENDAR 1. I have already started implementation by introducing the hydroids and their needs to my class. We will get into it more once my supply arrives and we have the right set-up for them. 2. I expect this project to last for a few months at least and hope to have it finished by February or March. 3. I will have to devote this project more time than I would devote to my other labs but it will be a continuous process, touching up on the progress almost every day. This will require a lot of work on my part since I will have to perform the microsurgery and having only one stereomicroscope at school, it will be hard for the class as a whole to do the experiment. For my 9th grade students, I would like to take them to Dr. Dudgeon’s lab twice a week and train them on working with the organisms and getting the technique mastered (which will also take a lot of my time). MATERIALS 1. I will need a supply of the hydroids, some very thin brushes (which I have bought), aquarium supplies to maintain the hydroids (bought), Dextran solution for the experiment, and I’m hoping that I can convince my principal to purchase at least a second stereomicroscope. 2. I wish I could borrow the microscopes from somewhere (I don’t know if CSUN could come up with a policy to do that). That way I would be able to involve the whole class in separate groups. 3. I’m ordering most of the supplies from Scientific Supply companies like Carolina and Fisher. I’m also in contact with a representative from Zeiss to look for demonstration or reconditioned microscopes. CURRICULAR MATERIALS The only website I have found so far is called the Hydroid Page by Yale University professors. The website is http://pantheon.yale.edu/~lfc6/hydroid.html. I will try to provide my students with books that discuss the hydroids since most of the information may be too technical or too advanced for their level. DISSEMINATION PLANS 1. My students will post their results periodically on the CSUN NSF website to share it with others. We will also be communicating frequently with Bernice Krieger at Pacoima Middle School since I worked with her over the summer on a similar project in the lab of Dr. Dudgeon. Her students will be doing similar experiments and we will compare our results and keep each other posted. 2. I will try to have my students finish their projects before February 1, 2000 for publication of their abstracts. 3. The projects will definitely be ready for the June 2000 Poster Fair. |
