Why don’t boas choke?

Boa constrictor (boa) can reach four meters in length and weigh about thirty kilograms. This formidable predator encases its prey between rings, resulting in a drop in blood pressure and severe bradycardia. The blood supply to the organs is cut off. After death, it swallows its prey whole. However, this behavior (squeezing and swallowing) can logically also interfere with ventilation in these snakes at the same time. Therefore, American and Australian researchers suggested that “that the first kites had to bypass these mechanical limitations“, – write in an article published on March 24, 2022 in Journal of Experimental Biology. But how ?

Constriction partly responsible for the success of boas

Snakes – characters history of success scalable. More than 3,700 species are known, which have spread to all continents except Antarctica. The reasons for this success have not yet been clearly established, but the constriction technique may be one explanation. These reptiles are capable of overcoming prey heavier than them.

Squeezing, swallowing and digesting large prey can inhibit lung inflation in space and time.” and hence from “sgreatly restrict the movement of the ribs and body walls necessary for ventilation“, note the authors of this new study. To better understand the trick used by the boa constrictor, the researchers used several different imaging techniques. live. They needed data on the movement of air in the snakes’ bodies, the activation of their muscles, and the various movements of their ribs.

Segmental ventilation

Biologists have found some evidence to support their initial hypothesis that boas independently control the movements of ribs in different parts of the thorax in response to movements that are hindered by swallowing or killing prey. They don’t have a diaphragm, but they use the muscles that lift the ribs.”a key innovation allowing the use of modular ventilation mechanics, at least in snakes.

Each muscle of this type can simply lift one rib. Thus, when a part of their body is used to suppress or swallow prey, another free part is responsible for breathing. However, the latter is not as effective depending on the part of the lung used (boas have an atrophied left lung and a long effective right lung). Gas exchange (carbon and oxygen) actually occurs only in the first part of the right lung. “The posterior two-thirds of the lung cannot carry out gas exchange and are just a bag.“, – explained live science John Capano, lead author of the study.

The researchers also made discoveries from a neurological point of view. Thereby, “the isolated rib movements demonstrated in this study indicate that the respiratory centers of the central nervous system selectively activate musculature around certain ribs, suggesting a previously undescribed neural feedback control in snakes.the study adds. The researchers speculate that this segmented pulmonary ventilation was necessary so that the snakes could then take over the constriction and swallow large prey.

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