The Animals

A to Z of animals


Researchers have found that the core body temperature of the armadillo is low enough to favour the growth of the leprosy-causing bacteriumMycobacterium leprae. Using the armadillo, scientists have been able to develop a vaccine against leprosy, and one day these unusual South American mammals could help to provide a cure for the disease.

The natural products of bees, such as royal jelly, honey and even their venom, have been found to have significant effects in cancer treatment and prevention. The application of these products inhibited tumour growth and increased survival of the animals they were tested on. These results may lead to human clinical trials using royal jelly or honey, combined with chemotherapeutic agents.

Studies on cats have given researchers better understanding of eye disorders like amblyopia (lazy eye) and strabismus (cross-eye). Cats have also contributed to research on glaucoma and cataract surgery. Because of similarities between the neurological system of the cat and that of humans, cats make excellent models for studying the spinal cord and vision and for other types of research involving the nervous system. 


It was first discovered that diabetics lacked the hormone insulin through studies in dogs - the results of which earned scientists the Nobel Prize in the 1920s. Both cats and dogs were important in the development of the heart-lung machine which made open-heart surgery possible. Later, dogs were the first animals used in the attempt to conquer the rejection of transplanted organs. Once again, a Nobel Prize for medicine (1990) was awarded to researchers who studied the immunological basis of organ rejection using dogs. Dogs are still important in heart research and in the safety testing of new medicines. 

A century ago, horses were used to produce an antitoxin to treat diphtheria. This was the forerunner of diphtheria vaccination. Scientists have cloned the first member of the equine family: a mule, a cross between a mare and a donkey. The first cloned mule, Idaho Gem, was born in May 2003. This mule clone may help shed some light on human cancers. There are close similarities between humans and horses at the cellular level, which could provide a number of insights about how the relationship of certain chemicals in the body affects both normal and abnormal cell activity.

Because ferrets are domesticated and their oestrous cycle is similar to the human menstrual cycle, they have become important in reproduction research. In particular, they have been useful in determining the environmental factors that influence seasonal reproductive activity and the physiological factors which control puberty and ovulation. In addition, they have been used to study the control of sexual differentiation in the brain, auditory research, as well as to develop a bird and swine flu vaccines and anti-emetics for cancer patients. 

Guinea pig

Guinea pigs have contributed to 23 Nobel prizes for medicine with studies leading to the discovery of Vitamin C, the tuberculosis bacterium, and adrenaline, as well as the development of vaccines for diphtheria and tuberculosis, replacement heart valves, blood transfusion, kidney dialysis, antibiotics, anticoagulants and asthma medicines. Today, guinea pigs are still widely used in medical research, particularly in the study of respiratory, nervous and immune systems. 

An interesting use of hamsters in medical research is the study of the neural basis of our internal daily (circadian) rhythms - in humans this controls our sleep-wake cycle over a 24hr period. The control centre for these rhythms was found in the hypothalamus of the brain, and the use of hamsters clearly demonstrated the role of the hormone melatonin in this daily cycle. 

One insect widely used in scientific and medical research is the fruitfly, orDrosophila melanogaster, a 3mm-long insect of the kind that accumulates around spoiled fruit. It has been used in genetics and developmental biology for almost a century, and today several thousand scientists are working on many different aspects of the fruitfly. Its importance for human health was recognised by the award of the Nobel prize for medicine in 1995, for work on the genetic control of early embryonic development. Mutant flies with defects in any of several thousand genes are available, and the entire genome has recently been sequenced. These creatures have also helped to develop drugs designed to combat pathogens responsible for a range of diseases from skin infections to pneumonia and meningitis. Recent research with fruitflies has focused on the pathology of Alzheimer's disease; although the flies have a very simple brain they have highly developed muscles and nerves.

These ocean creatures may have a painful and sometimes deadly sting, but they have proved to be very useful in scientific and medical research. Some researchers have used jellyfish to search for an effective anti-venom to save victims of Sea Wasp stings, whilst others are studying the chemicals in jellyfish for possible use in treating cancer. A bioluminescent chemical found in a type of jellyfish from the Pacific has already allowed doctors to trace the movement of specific chemicals through the body and could help reveal ways to inactivate defective genes, such as those in Huntington's disease.

Researchers have recently sequenced the genome of these Australian marsupials, allowing the identification of regions of similarity and difference that can provide clues about the structure and function of genes vital to human health and development. Kangaroo meat is the best source of CLA (conjugated linoleic acid) - a healthy fat which possesses potential anti-carcinogenic and anti-diabetic properties, in addition to reducing obesity and high blood pressure. Studies are now underway to determine what is responsible for CLA formation and why kangaroo meat contains so much. If successful, it may be possible to increase the CLA content of other meats and products to increase potential health benefits to consumers.


Rabbits and hares are lagomorphs. Rabbits are often used in research into respiratory disease such as asthma. Cystic fibrosis - a genetic lung disease - has been investigated using rabbits in addition to mice. At present, researchers are assessing whether gene replacement therapy could prevent cystic fibrosis in newborn rabbits, which could have a huge impact on therapies for patients with the condition. Rabbits are commonly used to produce antibodies and in safety testing. 


Mice are the most commonly used vertebrate animals in medical research. This trend looks likely to continue now that both mouse and human genomes have been mapped (80% of human genes are exactly the same as those found in mice, and at least a further 10% are very similar) allowing human genetic disorders and diseases to be studied with greater accuracy. Often, the only way of determining the function of a human gene is to insert it into, or remove it from, the mouse genome. Many thousands of mouse strains now exist, some frozen as embryos. Eventually, such techniques could lead to new methods of preventing, treating or even curing genetic diseases and other diseases with a genetic component. 92% of all genetically modified animals used in research are mice.

Nematodes, like C. elegans, have 'wormed' their way into scientific history, significantly contributing to the research carried out by three winners of the 2002 Nobel Prize for medicine. Despite having a relatively small number of cells, these flatworms still have a nervous system that even includes a primitive brain, making them ideal for studying the development of nerve cells. C elegans was the first animal to have its genome sequenced, back in 1998.

The Animals (Scientific Procedures) Act 1986 regulates scientific procedures which may cause pain, suffering, distress or lasting harm to "protected animals"; it refers to these as "regulated procedures". Protected animals are defined in the Act as all living vertebrate animals, except man, as well as one invertebrate species, the common octopus. The octopus has added 12 years ago after extensive discussion concluded that its well developed nervous system may make it capable of feeling pain. However, no regulated procedures have been carried out using the octopus since its inclusion. 


The release of the pig genome sequence has resulted in an increase in medical research using these intelligent animals. Stroke research is just one area in which pigs and miniature pigs have generated new insights. Transplanting genetically modified pig cells could hold the key to treating patients with stroke, and indeed other brain disorders, like Parkinson's disease. This process of transplanting genetically modified animal tissues, cells and organs into humans (xenotransplantation) has potential for treating a number of diseases. Pig heart valves have been used for many years to replace diseased or damaged human heart valves. 

Research into head and facial development is an important use of quails. In one study, the embryos from both quails and ducks were used to implant neural crest cells (simple cells that arise very early in development) from one species into the other. The result was quails with duckbills or 'duails', and ducks with quail beaks or 'qucks'. This suggests that head and facial diversification is due to neural crest cells, and further work should help to unravel the underlying causes of craniofacial defects, which are among the most common birth defects. Quails are also used to test the safety of agrochemicals in the environment. 


In 2004, the lab rat became the latest animal to spill its genetic secrets, and after man and mouse, was the third mammal to have its genome sequenced. This will further raise the rat's high profile in medical research, where it is the second most commonly used mammal after the mouse. Over the last century, the rat's image has been transformed from plague carrier to indispensable tool in experimental medicine and drug development. Rats have frequently been used in research focusing on cardiovascular diseases, psychiatric disorders, spinal injury, stroke, diabetes, surgery, transplantation, auto-immune disorders, cancer and bone healing. In drug development, the rat is routinely used to test the efficacy and safety of potential medicines prior to human clinical trials. 


A 6.6kg Finn Dorset lamb 6LLS was born after a 148 day gestation period on 5 July 1996; its name was Dolly. This animal is undoubtedly the world's most famous sheep: the first mammal cloned from an adult cell. Despite some controversy, the benefits of successful animal cloning could be enormous. Research aims to produce medicines in the milk of such animals, for example, the blood clotting agent factor IX for haemophilia or alpha-1-antitrypsin for cystic fibrosis and other lung conditions. Clones can also provide a greater understanding of the development of the embryo and of ageing and age-related diseases. Conventional sheep, and cattle, are also used in veterinary research. [37,795]


Cotton-top tamarin monkeys have a high rate of spontaneous colon cancer. They develop colon cancer in a very similar way to humans, so investigations of whether colon cancer is heritable - as it can be in humans - are now a focus of research. Other monkeys used in research include macaques and marmosets, mostly in brain research and in safety testing of new medicines. [marmosets & tamarins: 1,103, all monkeys: 4,688]

The study in sea urchins of the molecular processes that drive cell division in all organisms led to the Nobel Prize for medicine in 2001. Scientists have found that the key to species-specific fertilisation in sea urchins is a sperm protein called bindin. While mammal eggs - mouse and human, for instance - don't have a thick jelly coating like sea urchin eggs, they do have complex sugars on the surface, and it is likely that these sugars attach to sperm cell proteins to trigger reproduction. Understanding the reproductive processes of sea urchins could lead to solutions for human reproductive problems, including new approaches to contraception.

Voles are commonly used in studying social traits. A particular gene that produces a protein called vasopressin in their brains contributes to these behaviours. Adult male offspring with the long version of the gene have more of the protein in brain areas involved in social behaviour and parenting. These males tend to investigate female odours, greet strangers more readily and nurture their young. So variability in the length of the gene could help account for differences in normal human personality traits, such as shyness, and could perhaps influence conditions like autism and social anxiety disorders. [up to 1,533 in the 'other rodents' category which also includes shrews]

Watanabe rabbit
Medical researchers are indebted to the Watanabe rabbit - a breed that suffers from a rare genetic defect causing fatally high levels of blood cholesterol. A similar gene defect in children causes cholesterol levels between three and seven times higher than normal, usually leading to death before their teens. Watanabe rabbits have been used in the development of an artificial liver to remove excess cholesterol from the blood of these children, and are proving crucial in the search for better treatments. 


Xenopus Laevisis a species of frog native to Africa, which was used for many years as a biological assay to determine human pregnancy; female Xenopus respond to a hormone present in pregnant women's urine (chorionic gonadotrophin) by laying eggs. They are still vital in vertebrate biology, where they have been used to identify how cells become specialised for certain functions within the body, and how these cells contribute to the structure of the body during embryonic development. In cell biology and biochemistry, they have proved essential in studying chromosome replication, control of the cell cycle, and various signaling pathways. [all amphibians: 14,467]

Yellow-beaked cleaner shrimp
When you're a small shrimp in the fish world, it pays to know how to dance. The yellow-beaked cleaner shrimps perform a special 'rocking dance' to advertise their parasite cleaning services to host fish. Dancing guarantees the tiny crustacean easy access to food. These tiny shrimps remove parasites from more than 35 different species of coral reef fish such as coral trout, rock cod and sweetlip and will even move in and out of their mouth and gills without being eaten. This research supports the idea that unrelated organisms can communicate with each other via advertising signals.


The zebrafish is important in studying develop-mental origins of health and disease. Their embryos are transparent and develop outside the body, allowing simple study of the developing embryo. Zebrafish research provides a unique visual approach to under-standing the developmental defects in adult diseases and age-related abnormalities, such as cardiovascular diseases. Fish are the third most commonly used protected species in research after mice and rats: other types of fish are widely used in safety tests for environmental protection. 

Source : Understanding Animal Research