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Tadpoles and using them to understand brains

Tadpoles as Pets

How to raise tadpoles into frogs

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Can I keep tadpoles at home?

Raising tadpoles at home is a great way to see how a frog develops. It can be a fun activity for all the family or your classroom. Before you collect the spawn you will need to have all the necessary equipment to keep your tadpoles happy and safe. Below are some 2 month old tadpoles. 

 

Markus-at-thinkoholic-IMGP0319-1f


What you need before you start

  • A clean plastic container or fish tank (4-5 litre capacity).
  • Pond or rain water (or even bottled water).
  • Tap water has chlorine in it which will kill tadpoles.
  • A calm space out of direct sunlight near a window or outside.

test tadpole care website


Where can I find frog’s spawn and tadpoles?

At the beginning of spring frogs mate in ponds and lay their eggs in clumps in shallow water.

Check the edges of ponds in gardens and nearby parks, or take a trip to the nearest woods and look for them in ponds.

  • Bring 2 clean jars with screw tops.
  • Lie down at the edge of the water and reach in to scoop up some frogs spawn or some tadpoles. Use the second jar to top up the water.
  • Try to collect some underwater plants. Put them in the other jar with more water from the pond. You can use this water to fill your tank.

Tollard-Royal-pond


What do tadpoles eat?

Young tadpoles feed by scraping at the leaves of pond weed. They also like fresh lettuce and baby spinach. Before you feed them, rinse the leaves thoroughly. 

tadpolefood

Tadpoles only need a little bit of food. It is very important that their water is clean all the time, so change the leaves if they start to look sad!

As tadpoles get bigger they will eat anything they can! You can feed them with flakes of fish fry food from a pet shop.

When tadpoles grow legs they become carnivorous (meat eaters). They will eat each other unless you provide meat for them. Small pieces of meat can be suspended in the water on a piece of string. Change the meat every day. Below are some tadpoles eating a dead snail.

Rana_temporaria_tadpoles_eating_Mariomassone


Caring for your tadpoles

Your tadpoles will thrive if they are properly cared for and you will see them grow. See some tips for caring for your tadpoles below.

Tips!

  1. Make sure the water is clean. Change the water if it becomes cloudy. Remember to only use rain water or water collected from a pond. You can use tap water if it has been allowed to stand for about three days.
  2. Try to keep the water temperature steady and between 15 and 20 degrees C (about 60-70 degrees F).
  3. Never change the water temperature suddenly as this is likely to kill the tadpoles.
  4. If you leave your tank outdoors or near a window make sure it is in a shady place.thermosideways_clipartfree

What’s next?

Later your tadpoles will gradually grow front legs, lose their tails, and transform into baby frogs. Baby frogs are sometimes called froglets. Here is a tiny froglet on a lily pad flower.

froglet_Nilfanion

When the tadpoles grow legs they will need a way to get out of the water. You can put some stones or twigs for them to climb. It might take 6-12 weeks for them to reach this stage.

Once they develop into frogs they are ready to be released at a site near a pond and after growing into adults they can start a new life-cycle. Click here to see the life-cycle stages of a frog.


Activities and resources

pencil22small_foka.tkLife-cycle diary

Click on the link below to print a life-cycle diary to fill out as your tadpoles grow:

Life-cycle-diaryf


Media credits: Arkive- as stated; Two tadpoles Markus@Thinkaholic; child holding tank-professorhouse.com; tadpoles eating snail Mariomassone; froglet on lily-Nilfanion.  

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

frog

         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.

Schools_Alevel_aIN

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:

synapse_labelled_blank

 

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Resting potential and action potential confusion!

General_Revisionstar

 

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?!

General_Revisionstar

 

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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