Such anomalies are quite rare, because a new case awarded a separate scientific article in the Journal of Fish Biology. Researchers from Michigan State University explain that more often scientists come across two-headed lizards and snakes, but this may not reflect the true picture.
“These animals,” says Michael Wagner, assistant professor and one of the authors of the discovery – often bred in captivity, therefore anomalies are easier to detect. ”
Sharks, unlike snakes and lizards, very rarely breed on in human eyes, and two-headed individuals tend to live very not for long and do not grow to adulthood.
A photo from open sources
The described specimen was recovered by one of the fishermen who caught the female bull shark and the uterus that opened it. These large fish viviparous, they appear at a time up to 13 fry and the length of the fish at birth is approximately 60 cm (adult – 3.5 meters). The two-headed individual was delivered to researchers and they didn’t even decided to reveal a unique find: to keep it intact and safety, biologists took advantage of magnetic resonance tomograph.
Tomography showed the presence of two different hearts, stomachs, and, naturally, all organs are higher. But the tail of this individual (or individuals?) was common – a detailed study of such rare copies can help to understand the general patterns of development embryos and shed light not only on abnormal, but also quite normal physiological processes. Research by geneticists fruit flies with extra legs instead of eyes at one time allowed to discover the genes responsible for determining in embryos as head-tail axes, and finer separations – Hox genes responsible, for example, for the development of fingers on the limbs.
Ecology has nothing to do with it
Separately, Wagner warns that you should not bind find with environmental pollution. Yes, the fish was caught in Gulf of Mexico, where an oil spill previously occurred. But after” does not mean “due to” – as already mentioned, many animals regularly gives birth to similar two-headed cubs and in the most favorable conditions. Moreover, even a person has about a third all fertilized eggs leave the uterus without even being integrated into its wall – and the reason for this is including anomalies development; in all animals, including us, is built-in a natural defense mechanism against critical development errors.
A photo from open sources
By the way, congenital anomalies like two-headedness or irregularly shaped limbs – not necessarily mutations. Moreover, mutations are not identical to hereditary violations, therefore above in the text you will not see any suggestions about the “mutant shark caught by scientists.” Start with mutations as the most popular concept.
What are mutants? We are with you.
Mutations are DNA changes that are not nearly as rare as it is customary to think – any newborn child has about fifty to 3.5 billion nucleotide pairs; most mutations harmless and do not manifest themselves. Another part is harmful or lethal, but some, on the contrary, are beneficial. Or what happens also quite often, can benefit in certain conditions. African people, for example, often have a gene that increases resistance to malaria – but at the same time increases the risk sickle cell anemia.
Each gene exists in several varieties (alleles, like say genetics) and often you can’t say which one is “better.” Malaria risk or risk of anemia – which is worse? High probability melanoma or vitamin D deficiency? Some unsuccessful genes now causing, say, exposure to Alzheimer’s, could a thousand years ago to save from a long-forgotten disease, and the natural selection acting on South Africans hardly suggested their resettlement in cloudy northern countries.
Where do deformities come from?
Two-headed fish could appear without any genetic anomalies – just at the right moment in time the cells of the embryo divided once again or moved to the wrong place. Such failures are quite rare, but not impossible; their probability increases when exposed to certain chemicals – sad A well-known example is the thalidomide catastrophe. Very important understand that such violations cannot be transmitted by inheritance!
Inheritance without mutations
More recently, genetics divided hereditary and genetic diseases. In all our cells the same set of genes, however in each particular tissue they include only those genes that are needed for specific tasks – heart cells don’t need liver cell enzymes at all hard shell of osteocytes, bone cells. Every gene can be turned on or off due to reversible (unlike mutations!) chemical modification of DNA or rearrangement of chromosomal proteins.
These “switches” are inherited and it is proved that in in some cases, such an inheritance leads to increased risk certain diseases. Maternal smoking during pregnancy can increase the risk of asthma not only in a child, but also in grandchildren – at least a similar effect has been demonstrated in rats.
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