Meet the Scientists

We use very young tadpoles of the South African Clawed toad or frog (Xenopus) to study how brains work. Our research is supported by multiple funding bodies, including grants from the Biotechnology and Biological Sciences Research Council (BBSRC), the Wellcome Trust, and the Royal Society.

Read on to meet the scientists and explore the lab.

The Laboratory

Our laboratory is in the Bute Medical Sciences Building in St Mary’s Quad, off of South St in St Andrews in Scotland. The building was built between 1897-1899 as the medical school for the university, but was repurposed after a larger medical school was needed.

The facilities in the labs include areas to raise tadpoles at different temperatures, to make instruments for dissection, to take videos of tadpole behaviour, to prepare and mount brains on microscope slides, to wash glassware and stations to record electrical activity in the tadpole nervous systems. There is also a frog room where female and male frogs are induced to mate, so there is a steady supply of tadpoles to be studied in the lab.

The Scientists

The lab is headed by Dr Wenchang Li and Prof Keith Sillar.

Dr Wenchang Li is preparing a tadpole for recordings.
Valentina Saccomanno is processing some tadpoles to visualise the anatomy of neurons.
Dr Hongyan Zhang is recording the electrical activity from tadpole neurons.
Prof Keith Sillar is happy with some tadpole swimming activity he has recorded.
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Here are some of the researchers from the Bristol lab. Unfortunately, the lab is now closed due to the retirement of the head researchers Dr Steve Soffe and Prof Alan Roberts.

Dr Stella Koutsikou now is a senior lecturer in the University of Kent.

Mark Olenik is now working at Leibniz Institute on Aging.

The Frogs and Tadpoles

The tadpoles we study are produced by a small colony of adult Xenopus laevis looked after by the University Animal Services Unit. Animal research is strictly regulated by the UK Home Office under the Animals (Scientific Procedures) Act 1986. Universities carrying out animal researches are subject to frequent inspections by the UK Home Office who examines all aspects of animal research, care and welfare. The local Animal Welfare Ethics Review Body (AWERB) offers on-going support and guidance to researchers on best practice for animal involvement, welfare and refinement.

Below is a picture of one of the rank systems we use, which contain tanks which house toads in a carefully controlled environment.

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A frog rack system

Twice a week, mating is induced by injecting a pair of adults with the hormone human chorionic gonadotropin in the late afternoon. If all goes well, the pair are clasped and eggs (about 1 mm across) have been laid by next morning. The frogs have identity reference numbers and the number and quality of their eggs, as well as their weight is tracked. The data are used to determine which frogs mate best together.

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Mating Clawed Toads or Frogs with eggs. The female is larger and the male clasps her around the waist. He can then fertilise the eggs as they are laid. Frogs are slippery due to the protective muscus glands in their skin. Male frogs have specialised skin on their forearms (called nuptial pads) to help them effectively clasp onto females.

The fertilised eggs stick to the sides or bottom of the tank. We collect the eggs and take them to the lab to grow into tadpoles. Find out more on our Tadpole Laboratory page.

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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