Dr. José María Gutiérrez Gutiérrez, retired researcher and former professor at the Clodomiro Picado Institute (ICP-UCR) and the Faculty of Microbiology of the UCR. He is part of a group of world-class researchers who sought to decipher the composition of the venom of one of the most dangerous snakes on the planet.
Along with 28 other specialists from the UK, USA, Australia, the Netherlands, Spain, Norway and Brazil. The results of this important study were recently published in the journal Science, which explains why spitting cobras modified the composition of their venom as a defence mechanism. This aspect, from an evolutionary biology perspective, is not usually considered in snakes.
The spitting cobra and its venom.
The spitting cobra uses venom ejection as a method of defence. However, they are the minority of the cobra family to do so. The venom it sprays is not harmful in contact with the skin of any mammal, but it can blind it if it comes into contact with the eyes; and if not treated in time it can cause chemosis and swelling of the cornea.
Venom is sprayed in distinctive geometric patterns as the muscles squeeze the glands to spit forward through holes near the tips of the fangs.
When these cobras feel cornered they “spit” their venom up to 2 m away. Spitting is their main form of defence but they can also inject their venom by biting like any other type of cobra.
The Costa Rican team’s work is part of a larger investigation being coordinated by the Centre for Snakebite Research and Interventions (CSRI) at the Liverpool School of Tropical Medicine (LSTM). In order to discover why only the spitting cobra variety had opted for this unique defence mechanism among the extended family of cobras.
According to Dr. Gutierrez, snake venoms have several functions. One of them is to immobilise and subjugate prey. The toxins help to paralyse the prey, or produce tissue damage to immobilise it. In this way, the snake can ingest the animal that will become its food.
However, there is another little-studied purpose of venoms, and that is their defence function against predators. Understanding this was the main objective of the research.
Results: Convergent Evolution.
The scientific paper published in the journal Science says: In three different groups of cobras (one from Asia and two from Africa) they managed to obtain the same characteristic of spitting venom. This evolutionary strategy occurred at three different times, millions of years apart and with proven geographical remoteness.
In other words, this pattern of defence did not occur in a common ancestor of the three species studied, but completely independently, a phenomenon known as evolutionary convergence.
“One in a group of cobras in Africa, between seven and eleven million years ago. Another in Asia, between two and four million years ago, and a third group in Africa. All three are independent events but with the same characteristic. These groups of cobras, although they were at different times, managed to change their fangs and modify the orifice in order to eject the venom from the front” Dr Gutiérrez added.Source University of Costa Rica
Other examples of evolutionary conversions occur when different species or species separated by long distances or geographical barriers solve common problems in the same way. Such as the swimming selection of some mammal species, the development of similar beaks based on feeding function, or the flight of birds and bats.
Better defence and a better poison.
But spitting cobras not only adapted their fangs with small holes to expel their venom over long distances.
The research team found that the spitting cobras studied had independently increased production of phospholipase A2 (PLA2) toxins. In order to enhance the defensive capabilities of their venom.
“What is interesting in the evolutionary history of cobras is that they first develop this behaviour of positioning themselves vertically to defend themselves. Then they generate cytotoxins that allow them to defend themselves by biting because they produce pain. But then they develop another mechanism, which is to spit out the venom and subsequently improve its composition to generate more pain in a very efficient way,” Dr Guitérrez said.Source University of Costa Rica
The Clodomiro Picado Institute and snakes.
The Clodomiro Picado Institute, attached to the Faculty of Microbiology of the University of Costa Rica, was founded in April 1970. The realisation of this project, however, has its roots several decades ago, mainly in the pioneering efforts of the famous national scientist Dr. Clodomiro Picado Twight (1887-1944).
While working in the Clinical Laboratory of the San Juan de Dios Hospital, Picado became interested in the subject of snakebites. From this, he developed an intense research programme on snakes and their venoms, as well as in the search for new solutions to the problem of ophidian poisoning suffered mainly by the country’s peasants.
Since its foundation Clodomiro Picado has created serums and antidotes for snakebites which are used extensively in Costa Rica and around the world.
The trajectory and prestige achieved by the Clodomiro Picado Institute is confirmed by the awards received throughout its history, which constitute a recognition of the knowledge developed during research with a social purpose, a beneficial academic link with future generations of scientists and researchers in the country and a leadership earned in the field of ophidianism and the production of antivenoms.
More recently in 2020 during the first wave of the Covid19 pandemic, I also created thousands of vials of convalescent serum based on human blood plasma and equipment to improve the chances of survival of moderate and severe Covid19-affected patients.