. The comparative physiology of respiratory mechanisms. Respiration. 136 RESPIRATORY MECHANISMS sion could take place, and the animal became heavier than water in 14 minutes and died in 35 minutes, although when breathing ordinary air at the same temperature it could subsist for 6 hours Without access to the surface. This respiration mechanism is essential for several small aquatic insects belonging to different groups and also for some larger ones in winter when the metabolism is low. Several species of Dytiscidce move about vigorously under ice and supplement their store of air by catching b
. The comparative physiology of respiratory mechanisms. Respiration. 136 RESPIRATORY MECHANISMS sion could take place, and the animal became heavier than water in 14 minutes and died in 35 minutes, although when breathing ordinary air at the same temperature it could subsist for 6 hours Without access to the surface. This respiration mechanism is essential for several small aquatic insects belonging to different groups and also for some larger ones in winter when the metabolism is low. Several species of Dytiscidce move about vigorously under ice and supplement their store of air by catching bubbles rising from plants, or from the mud. Even if these latter contain very little oxygen they may be essential for keeping up the quantity of gas on which the uptake of oxygen from the water depends. The animal which is prob- ably most definitely adapted to obtain oxygen by diffu- sion into a layer of air is the spider Argyroneta which al- ways carries a layer of air round the whole of the abdo- men and part of the thorax. In this case the air sometimes lasts for several days even in summer (Braun, 1931). Respiration from aquatic plants. A small number of beetle and Diptera larvae are able to obtain air for their respiration from aquatic plants, not only by collect- ing bubbles, but directly from the intercellular spaces. I have had an opportunity to make some observations and experiments on the larva of the mosquito Mansonia shown in Figs. 77 and 78. The atrium of the spiracle is drawn out into a tube of hard chitin with a sharp cutting edge. This is placed against the root or rhizoma of an aquatic plant and,. Fig. 77. Mansonia larva on plant root. Ca. 10/1. (Wesenberg-Lund.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Krogh, August, 1874-1949. Philadelphia, University of Pennsylvania press
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