Hatchling Xenopus Tadpole motor behaviors

Xenopus laevis is the latin name for the African Clawed toad


Hatching

After two days in the egg Xenopus are about 5mm long and have usually hatched. Like the British frog tadpoles (Rana temporaria) they then hang about for a day or so doing very little. They stick themselves to plants or other objects, like the side of a tank, with mucus secreted by a black cement gland on the head where the mouth will form (red arrow).

The mucus is not very strong, so periodically (on average once every 30 minutes) they come unstuck and fall through the water. In shallow water they may come to rest on the bottom.

Swimming

If not attached by mucus, tadpoles often start to swim spontaneously but they will also swim if touched or stroked gently anywhere on the body with something which will indent the skin like a fine hair. During swimming the trunk muscles on each side of the body contract in alternation and contractions start at the head end. As a result, waves of bending pass from head to tail, alternating at from 10 to 25 Hz and driving the tadpole forwards through the water. Stronger and damaging stimuli to the skin (e.g. blue laser in the video below), a brisk water current directed at the head and dimming the light will also start swimming which can last for many seconds.

Tadpole swimming evoked by a blue laser light. Tadpole first responds to the hot laser with a few alternating muscle contractions. After a little pause, it turns around and swim away. Video is slowed down by 32 times from 240 fps. The blue halo is produced when the laser is not blocked by the tadpole trunk and becomes out of focus.

Stopping

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 object like a plant or the side of a dish (see video clip below). 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.

Xenopus laevis tadpole swimming stops when its head clashes into a petri dish wall. gridlines at the bottom of the dish are one millimetre apart. The tadpole swimming starts when it is dropped into the petrid dish.

Struggling

Like many adult fish, when a tadpole is grasped and held anywhere on its body it makes strong, slow side to side bends of the body to try to wriggle free. This is most reliable when the tadpole head region is held. We call this behaviour struggling (see the videos below).

The tadpole is held between two insect pins. It starts to produce the struggling behaviour when both sides of the head region are pressed. Once it is free from the hold, the tadpole coil it body a few times before swimming away. Video is 240 fps.

Compared to swimming the frequency of the bending movements is slower (5 to 10 Hz), and the waves of bending move in the opposite direction, from the tail to the head. This can be seen more clearly when the video is slowed down by 8 times below:

The same video as above but the play speed has been slowed by 8 times (from 240 fps to 30 fps).

The Digestive System


 

The digestive system is modified to account for the change of the herbivorous diet of the tadpole to the carnivorous diet of the frog.

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The Skin


 

The skin adapts for the change from a purely aquatic lifestyle to an amphibious lifestyle.

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The Reproductive System


 

The urogenital system develops to allow for reproduction in adulthood.

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The Skeleton


 

The skeletal structure develops to accommodate the change from tail swimming to using legs to move around. The skull also needs to be remodelled for a frog's change in vision.

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The Nervous System


 

A tadpole sees from eyes that are positioned on opposite sides of the head. During metamorphosis, the optical nerves develop to accommodate a frog's binocular vision, where the eyes are positioned at the front of the head.

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1. Mating and Laying Spawn


 

Male and female frogs go to ponds in the winter. They mate in the spring, and the female lays big clumps of eggs.

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2. Frog Spawn


 

Frogs eggs are called frogspawn. Each round black egg is about 1 mm wide and is surrounded by a blob of jelly. Other animals produce spawn as well, which you can look at here.

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3. Maturing Frog Spawn


 

After a few days, the eggs begin to grow into tiny tadpoles inside the jelly.

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4. Hatchlings


 

Then the tadpoles hatch! They are about 5 mm long and they can’t swim (yet). They can bend their body from side to side using special muscles along their trunks and tails.

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5. Young Tadpoles


 

When their tail is big enough, they swim off into the pond to start to feed. At first they have gills (the pale protrusions from the head region in the left photo) so they can breath underwater like fish. Young tadpoles feed by grazing the surface of pond weeds and also eating tiny floating plants called algae.

Click here to play a tadpole feeding game called Taddypole!

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6. Maturing Tadpoles


 

Later they develop lungs and can swim up to the surface of the water to breath. The gills are absorbed back into their bodies and eyes develop. Older tadpoles are then able to feed on small animals like young insects.

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7. Mature Tadpoles


The next stage in development is to grow back legs. Tadpoles during this stage need to eat meat in order to get the proper nutrients to grow.

If you are looking after tadpoles, be careful as they can eat each other if you don't give them meat to eat! Click here to learn more about how to look after tadpoles as pets.

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8. Froglet


Finally, tadpoles grow front legs and their tail shrinks until it almost disappears. This is when they climb out of the pond and start living on dry land. Small frogs are commonly called froglets.

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9. Adult Frog


The little froglets will stay by the pond and slowly grow over the summer, eating small insects and worms. They will hibernate just like other adult frogs in damp spots near ponds from autumn until the next spring.

After four years, the new frogs will become adults and will be ready to mate and begin the cycle again.

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Copy - 9. Adult Frog


The little froglets will stay by the pond and slowly grow over the summer, eating small insects and worms. They will hibernate just like other adult frogs in damp spots near ponds from autumn until the next spring.

After four years, the new frogs will become adults and will be ready to mate and begin the cycle again.

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Desert Habitats


Desert habitats are the driest habitats in the world. Most people only think of very hot habitats as being deserts, but cold habitats can be deserts as well! Animals and plants that live in deserts have the ability to survive on very little water and animals can control their body temperatures so they stay at the right level.

 Some examples of plants and animals that live in deserts are cacti, the desert tortoise and the artic fox.

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Coral Reef Habitats


Coral reefs are found in warm tropical oceans all around the world. Coral reefs can be found in both shallow and deep water and take hundreds of thousands of years to grow! They provide food and shelter to many fish and other animals, making them habitats that are home to so many different types of life.

Some examples of plants and animals that live in coral reefs are the sea star, sea grass, the octopus and clown fish.

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