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Tadpoles and using them to understand brains

Tadpole pictures

Pictures, diagrams and photographs for your reports, projects, walls...


This page contains lots of drawings and photographs for you to use in your reports, projects, tadpole diaries or whatever you like. Click on the individual photo to print or copy. Please attribute work where appropriate (not needed unless reproduced on line, please refer to creative commons licence rules).

Very young tadpoles (Rana temporaria) developing in eggs- Lia Gilmour


Close up of very young tadpole (Rana temporaria) developing in egg- Lia Gilmour


Close up of very young tadpole flexing (Rana temporaria) in egg- Lia Gilmour



Young tadpole (Rana temporaria) with gills starting to form- Lia Gilmour


Young tadpoles (Rana temporaria) hanging by their adhesive glands- Lia Gilmour

twotadpoles at surface

Drawing of young tadpoles feeding


Underside of tadpole showing mouth, adhesive glands and gills- Lia Gilmour


Hatchling tadpoles flexing- Alan Roberts

Hatched tadpole flexes body after hatching 23 Feb 2016

Hatched tadpoles- Lia Gilmour


Hatchling tadpoles with spawn- Lia Gilmour


Young tadpole with gills visable- Lia Gilmour


Drawing of young tadpole with gills- Stephen Soffe


Young tadpole head showing gills- Lia Gilmour


Wood frog tadpoles- NatureNorth


Tadpoles- Markus @ Thinkaholic


Tadpoles in pond- Alan Roberts


Tadpoles in pond- Alan Roberts

test many tadpoles website

Tadpoles eating snail- Mario Massone


Tadpole- Animal Spot


Tadpoles swimming- Olaf Tausch

tadpoles swimming

Wood frog tadpole with back legs- NatureNorth


Tadpole with legs from old drawing


Tadpoles to colour in

colou-in tadpoles

Media credits under creative commons licence

Tadpole swims when touched at *

The details of swimming movements which hatchling Xenopus tadpoles make in response to touch with a fine hair  have been studied by making high speed videos at 200 fps. In these examples touch on the left (*) leads to a bend to the right followed by swimming. Waves of bending travel from the head to tail (at ~ 14 cm per second) and increase in amplitude as they travel along the body. They move the tadpole in the direction shown by the arrows. Swimming speeds at ~ 20 oC range from 4 to 6 cm per second.hatchling tadpole swims when touched at *

Kahn J.A., Roberts A. & Kashin S. (1982) The neuromuscular basis of swimming movements in embryos of the amphibian Xenopus laevis. J. exp. Biol.  99, 175‑184. http://jeb.biologists.org/cgi/reprint/99/1/175

Adult South Africal Clawed toad Xenopus laevis


         Xenopus laevis

What Tadpoles Look Like

Tadpoles can start swimming spontaneously or when they are stimulated but it is just as important that they can stop. This normally happens when their head and cement gland bumps into the surface of the water or some other solid tadpoles swimmingobject like a plant or the side of a dish. This kind of stimulus and the tension in the mucus strand when the tadpole is hanging attached have an inhibitory effect on the tadpole. While hanging, it never moves spontaneously and is much less responsive to stimulation. This ability to keep still may make it more difficult for predators to detect and eat tadpoles. 

Types of Neurons

There are different types of neurons in a nervous system and they are named depending on their function.


Interneuron from Xenopus laevis tadpole

Broadly there are 3 main types:

  1. Sensory neurons
  2. Motor neurons
  3. Interneurons 





Flexion behaviour of hatchling tadpole in response to skin stimulation (represented by arrow).

When the skin of Xenopus laevis hatchling is touched, sensory neurons are activated, passing on exitation to sensory pathway neurons (interneurons) in the spinal cord, which in turn excite motor neurons, causing flexion behaviour

For more info on research into flexion behaviour click here. 

Synaptic transmission (blank diagram)

pencil22small_foka.tkPrint and fill in the blank diagram with the key steps in the process of synaptic transmission:



Resting potential and action potential confusion!



The terms resting potential and action potential can be confusing, as they seem to suggest that one is an active process and the other not.


Action potentials are actually produced by a passive process- sodium ions diffusing into the axon, causing depolarisation. 

Resting potentials are generated by an active process, which needs ATP. The sodium-potassium pump carries out active transport of ions in and out of the axon to generate a potential difference across the cell and a voltage of -60/70 mV inside the axon.

So even though the axon is said to be at “rest”, an active process involving energy in the form of ATP is actually going on. And even though the action potential sounds like it needs energy, it is actually a passive process.

Make sure you are clear on this!

Axon, membrane or axon membrane?!



Some exam boards prefer you to mention simply the “axon”, others just the “membrane”, or the “membrane of the axon”. 


When we are talking about a difference in charge over an area, we always refer to what area that is- for example a potential difference over the axon membrane. 

Some exam boards will prefer you say that the “membrane” or “axon membrane is depolarised”…but others will be happy with just the “axon is depolarised”

Check what is preferred by your exam board and incorporate into your notes links below:





Exam Board Links

pencil22small_foka.tkClick on the links below to access the specifications for listed exam boards:







Toad spawn

Toad eggs are the same size as Frog eggs but are laid in a string, often among weeds in the pond. The string can be more than 1 meter long and contain a double row of eggs. Here is a photo of a small piece from a pond in Hampshire.

A small piece of toad spawn from a pond in Hampshire.

American Bullfrog

Below is an American Bullfrog. The Latin name of this frog is Lithobates catesbeianus. It is sometimes also called Rana catesbeianus. 

American_Bullfrog_(Rana_catesbeiana)_-_Algonquin_Provincial_Park_Ontario_By Ryan Hodnett Own work

Click here for more information on the American Bullfrog from the ARKive website.

Media credits: American Bullfrog-Ryan Hodnett