An international group of scientists led by the researchers with the Dobzhansky Genome Bioinformatics Laboratory of St Petersburg University and the University of Malaya at Kuala Lumpur has presented findings of their study of the Chinese and Malayan pangolins' genome. The results of this work published in the October issue of the Genome Research journal will help preserve the endangered species of these unique mammals.
Pangolins, or scaly anteaters, are an order within the class Mammalia now including eight species. Four of them are found in Asia, the other four — in Africa. These are unique mammals with hardened keratin scales over their body. When threatened, they curl up into a ball, thus protecting themselves from predators. Pangolins' appearance is similar to that of anteaters and armadillos: they also use a long muscled tongue to hunt ants and termites. Yet, these mammals are next of kin of predators, having separated from them 60 million years ago.
Having studied the pangolin's genome, the scientists found out that, in the course of evolution, certain genes in these animals had ceased functioning and transformed themselves into the so-called pseudogenes. These are primarily the genes responsible for teeth and vision. Biologists think that is probably a result of the pangolins' assuming new habits: today they are insectivorous and nocturnal animals, relying on their olfaction most of the time. This hypothesis is supported by a substantial increase in the number of olfactory receptor genes in the pangolin's genome that has been found in the course of the study.
The researchers have made yet another unexpected discovery. 'It has been found out that, unlike most mammals, scaly anteaters have no gene responsible for skin's resistance to diseases', said SPbU postdoctoral fellow Mikhail Rayko, one of the study leads. 'That makes us propose that pangolins' scales have developed not only as protective armour but also as skin protection against injuries or stress. Moreover, these scales are aimed at reducing pangolin vulnerability to infection'.
The Chinese and Malayan pangolins are listed as critically endangered on the IUCN Red List of Threatened Species. Despite the fact that today all of the eight pangolin species are protected, they are the most popular objects of illegal trade among the animals. They are used in traditional medicine, in decore and as gourmet items.
The findings of this study will be the basis for further research into pangolin genetics and evolution . They make it possible to evaluate their genetic diversity, to work out the best captive propagation strategies and, finally, to preserve these unique mammals.
The details of this study are provided in the paper 'Pangolin genomes and the evolution of mammalian scales and immunity', Genome Research.