Swallowing breathing
As a sip of breathing in is Zoology of in amphibians distinct type of lung breathing designated.
The special breathing technique results on the one hand from the lack of a rib cage ( ribs and diaphragm ) in this class of animals, on the other hand from the fact that their respiratory muscles are evolutionarily derived from the gill and hypobranchial muscles . The air inhaled through the nostrils into the oral cavity is pressed into the lungs according to the pressure pump principle . This happens through an interplay of opening and closing of the nostrils and the slit-shaped throat ( aditus laryngus or glottis ), through raising and lowering of the floor of the oral cavity, and through contractions of the trunk muscles and the lung walls. The breathing air can flow back and forth several times between the oral cavity and the lungs. The mouth always remains closed when breathing . Outwardly, the process becomes visible primarily through the throat oscillation characteristic of frogs, toads , newts and salamanders , i.e. the constant raising and lowering of the floor of the oral cavity, combined with swallowing movements.
In addition to lung breathing - or as an alternative to this - a special form of skin breathing takes place in the oral cavity of the amphibians , the so-called oral cavity breathing or throat breathing . The gas exchange takes place via the dense blood capillary network of the oral cavity mucosa . Oxygen from the air taken up into the oral cavity through the nostrils reaches the ventricle via the great cutaneous vein , while carbon dioxide is conducted through the great cutaneous artery to the oral cavity mucosa and exhaled again through the nostrils. Breathing in the oral cavity - just like skin breathing on the rest of the moist body surface - is of great importance for amphibians, especially when the metabolism is reduced , for example during the winter. Some species, such as the lungless salamanders , even operate their breathing almost exclusively in this way (general skin breathing plus oral cavity breathing). The permanent, rapid up and down movement of the throat sac (floor of the mouth) is a prerequisite for the functioning of this breathing technique and is its externally visible feature.
The amphibian can switch between oral cavity breathing and swallowing breathing - as long as the species has a lung. The outer skin respiration takes place constantly. It is not possible to say in general how large the proportion of the animal's oxygen supply depends on the respective form of breathing. This differs depending on the species and is also dependent on their living conditions and physical activity. Despite the simple, sac-like structure of the amphibian lung, it plays an important role in respiration in many species, as does the gas exchange via the skin surface. The actual oral cavity breathing has a complementary function.
In the larval stage , amphibians also cover their oxygen requirements through the skin, but otherwise mainly by means of external or internal gills . These are then normally "replaced" by the lungs in the course of metamorphosis .
literature
- Klaus Kabisch: Dictionary of Herpetology. Gustav-Fischer-Verlag, Jena 1990, ISBN 3-334-00307-8 , pp. 295 + 387.
- Andreas Nöllert, Christel Nöllert: The amphibians of Europe . Franckh-Kosmos, Stuttgart 1992, ISBN 3-440-06340-2 , p. 24 f.
- Wilfried Westheide, Reinhard Rieger (ed.): Special zoology, part 2: vertebrate or skull animals. 2nd Edition. Spektrum Akademischer Verlag, Heidelberg 2010, ISBN 978-3-8274-2039-8 , p. 133 ff.