Welcome to tadpoles.org.uk

Tadpoles and using them to understand brains

Tadpole Food

Find out what tadpoles eat at different stages of their life-cycle

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You are what you eat?

Some animals only eat meat. They are called carnivores. Some animals only eat plants and they are called herbivores. Animals that eat both plants and meat are called omnivores. Animals can also eat different things at different stages of their lives.

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Tadpole food

Frogs like to eat different things at different stages of their life-cycle. Below is a picture of a tadpole life-cycle, but for more detail, click here to access the life-cycle page.

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Small tadpoles

Once they have developed in the egg into a small tadpole, they make their way out of the jelly layer. Below are some newly hatched tadpoles.

Hatched tadpole flexes body after hatching 23 Feb 2016

As small tadpoles, they scrape algae off the surface of water plants and rocks, shown in the picture below. At this stage they are mainly herbivorousClick here to play Taddypole, a tadpole feeding game, where you munch your way through the pond and avoid being eaten yourself!

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Bigger tadpoles

Once they grow bigger and their legs develop they become carnivorous and feed on small water animals such as this tiny water flea, which measures about 1 mm in real life, but is blown up in this picture.

Daphnia_magna_Ayacop

They will also eat each other if there is not enough food around! Below are some tadpoles eating a dead snail. Click here to learn how to look after tadpoles as pets and give them the right food.

Rana_temporaria_tadpoles_eating_Mariomassone


Froglets and adult frogs

Froglets will eat small insects once they have left the pond. Adult frogs are mainly carnivorous and will also eat insects as well as slugs, snails and worms. Below is an old drawing of a frog about to catch a caterpillar with its tongue.

Rana_eating_olddrawing

 


Media credits under creative commons licence: cat-Laki10 clipart; human-clipartbest.com; sheep-dailyclipart.com; water flea-Ayacop; tadpoles eating- Mariomassone 

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

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Adult South Africal Clawed toad Xenopus laevis

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         Xenopus laevis

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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. 

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Types of Neurons

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

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Interneuron from Xenopus laevis tadpole

Broadly there are 3 main types:

  1. Sensory neurons
  2. Motor neurons
  3. Interneurons 

 

 

 

flex-behaviour

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. 

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Synaptic transmission (blank diagram)

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

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Resting potential and action potential confusion!

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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!

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Axon, membrane or axon membrane?!

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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:

 ⇒Edexcel

AQA

WJEC

OCR

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Exam Board Links

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

 

 ⇒Edexcel

AQA

WJEC

OCR

 

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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.

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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

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