Planarian Behavior Measurement – Motility

‘‘Under carefully controlled experimental circumstances, an animal will behave as it damned well pleases.’’
-Harvard Law of Animal Behavior**
Planarians are a rising star in pharmacology and neuroscience research. In fact, planarians were recently called “neuroscience darlings”.
(:-D)
In a previous post I published a short video demonstrating a kind of behavior that can be observed in planarians when they are exposed to substances such as nicotine. These seizure-like movements are rather useful to explore pharmacology in these organisms.
Another way of exploring planarian behavior is to measure their motility, as in how do they move “from here to there”. In 2001, Temple University’s Dr. Robert Raffa and collaborators published a methods paper where they describe a way of measuring planarian motility. They basically put a worm in a plastic dish and the plastic dish over a gridline; it looks something like this:

The squares are 1 cm long. Picture credit: Baldscientist.
Then they happily counted how many gridlines did the worm crossed or recrossed over a set time period, say 10 minutes. This short video shows how they move.
This other video shows a closer look. If you count the gridlines crossed per minute over a period of say, ten minutes, the data and the associated graph will look very similar to this:

Picture credit: Baldscientist and http://sciencefocus.com/qa/why-do-we-get-bored.
Here is the clever part. They did not just count the squares crossed per minute, they also calculated the cumulative crossings, as shown in the next figure:

Picture credit: Baldscientist.
Now we are talking. This is a much more useful figure because we can now quantify the worm’s motility. I once heard that if a picture is worth a thousand words a number is worth a thousand pictures… we can even distinguish between faster and slower worms, depending on what we treat them with:

Picture credit: Baldscientist.
What was that? You wanted another video, this time with many worms? Sure, you can find it here.

Picture credit: Baldscientist.
**Cited in: Maye A et al., (2007) Order in spontaneous behavior. PLoS One. 2(5):e443.
If you want to know more
Raffa RB et al., (2001) Quantitative assessment of dopamine D2 antagonist activity using invertebrate (Planaria) locomotion as a functional endpoint. J Pharmacol Toxicol Methods. 45(3):223-6.
Pagán OR et al., (2009) The flatworm planaria as a toxicology and behavioral pharmacology animal model in undergraduate research experiences. J Undergrad Neurosci Educ. 7(2):A48-52..
Pagán OR et al. (2006) Toxicity and behavioral effects of dimethylsulfoxide in planaria. Neurosci Lett. 407(3):274-8.
http://www.scientificamerican.com/article.cfm?id=flatworms-recall-familiar-environs-even-after-losing-their-heads