What is the reaction time variation of Daphnia depending on changes in light stimulus location ?
We chose to study the variation of reaction time of Daphnia individuals when they are exposed to increasing color-alternating frequency.
But after a little research, we observed that information about phototaxis (behavior under light conditions) with Daphnia is unclear and sometimes sources contradict others sources.
“Animals reacted to ultraviolet light (260±380 nm) with negative phototaxis, whereas visible light (420±600 nm) caused positive phototaxis.” U. C. Storz and R. J. Paul in “Phototaxis in water fleas (Daphnia magna) is differently influenced by visible and UV light” in 1998.
But we can see in this video, and in other sites that the positive phototaxis (reaction to light) appears with blue light, and red light has no visible effect…
Preparation of our experiment
For our experiment, we tested the reaction of Daphnia to the red and blue light. We designed an arduino code to be able to alternate blue and red light during at a given frequency. We also designed a code to be able to write data collected by an RGB sensor (TSC 3200). The totality of our codes are on Github.
Wednesday (18/01/2017), we bought Daphnia at Truffaut, but were disappointed when we saw that they’d almost all died. We must wait until Thursday to begin the experiment with new organisms.
First experiment
Thursday morning, we saw only juvenile daphnia move in the water. We collected about 20 of them, put in a beaker of de-chlorinated water. During all the experiment we observed no vertical migration like we had hoped.
Final experiment: Friday (20/01/2017)
We put twenty adult Daphnia in a large petri-dish with a diameter of 13,7cm and we traced areas on a piece of paper at the bottom of the container. We alternately turned on blue LED that were placed on opposite sides of the plates and timed how long it took for five daphnia to swim into our target areas underneath the lights.
We choose to make lights switch every 1,30min, 2min, 3min, 3.20min, 4min and 4,20min.
For our first panel of daphnia, we observed a small area and we tried with shorter times than 1.30, but the daphnia did not have the time to migrate fast enough, so we chose to extend our target area of observation and decrease our alternance frequencies.
We performed controls by having one experiment where both light sources were on simultaneously and another where no light sources were on. We then observed how the Daphnia were placed throughout the Petri dish and confirmed that the light did have a noticeable effect on migration behavior.
During the afternoon, we did not have access to the laboratory, so we did an experiment with the electronic sensor in a room with a low quantity of light, and we put the sensor and the LED installation in a box.
We took 5 measurements for each of the different frequencies of lighting.
We recorded the measurements just before the changing of light to be able to have measurements according to time and see values stabilisation of the sensor.
We performed positive and negative controls with the sensor by conducting the experiment once with only red light, once with only blue light and once without.
This confirmed that the reaction we were observing was truly due to the changes in light during other experiments.
We could then determine the time needed for the stabilisation of the sensor’s data.
We determined that the sensors’ reaction time was between 10 and 20 milliseconds and was a constant. We obtained these results with the sensor:
For the experiment with Daphnia, we obtained these results:
Results received from experiments with Daphnias showed highly variable reaction times, but no clear correlation between these variations and the frequency of the alternating lights. This is perhaps because our method of measuring individuals was very imprecise and that the organisms did not always behave as expected, perhaps due to wear or other factors that were not taken into account.
If you want to learn more :
Github
Storify
Twitter
If you want to learn more :
Github
Storify
Sources :
Ebert, Dieter. Introduction to Daphnia Biology. National Center for Biotechnology Information (US), 2005. https://www.ncbi.nlm.nih.gov/books/NBK2042/.
Cellier, S., M. Rehaïlia, J.-L. Berthon, et B. Buisson. « Le rôle de l’œil, dans les rythmes migratoires de Daphnia magna et Daphnia longispina (Cladocères) ». Annales de Limnologie - International Journal of Limnology 34, no 2 (1 juin 1998): 159‑64. doi:10.1051/limn/1998015.
KN, Zhang L. and Baer. « The influence of feeding, photoperiod and selected solvents on the reproductive strategies of the water flea, Daphnia magna. - PubMed - NCBI ». Consulté le 20 janvier 2017. https://www.ncbi.nlm.nih.gov/pubmed/15092821.
Storz, U. C., et R. J. Paul. « Phototaxis in Water Fleas (Daphnia Magna) Is Differently Influenced by Visible and UV Light ». Journal of Comparative Physiology A 183, no 6 (1 décembre 1998): 709‑17. doi:10.1007/s003590050293.
« Check out the course “Tableaux et jeux de lumière avec plusieurs LED” on OpenClassrooms ». OpenClassrooms. Consulté le 20 janvier 2017. https://openclassrooms.com/courses/programmez-vos-premiers-montages-avec-arduino/jeux-de-lumiere-et-tableaux-avec-plusieurs-led.
« Sequential_blinking.ino ». Dropbox. Consulté le 20 janvier 2017. https://www.dropbox.com/s/bivwdnehp7ln1iq/Sequential_blinking.ino?dl=0.
« Éliminer le chlore de l’eau du robinet gratuitement ». consoGlobe, 7 mai 2016. http://www.consoglobe.com/eliminer-chlore-eau-robinet-gratuitement-2895-cg.
« Anatomy of a Mini Breadboard - Pimoroni Yarr-niversity ». Consulté le 20 janvier 2017. https://learn.pimoroni.com/tutorial/170pt-projects/anatomy-of-a-mini-breadboard.
« Arduino Color Sensing Tutorial - TCS230 TCS3200 Color Sensor - HowToMechatronics ». Consulté le 23 janvier 2017. http://howtomechatronics.com/tutorials/arduino/arduino-color-sensing-tutorial-tcs230-tcs3200-color-sensor/.
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