Tracheal system

Murray further explains that the inner surface of the larval trachea is composed of a waxy material, which is wetted by oil but not by water. According to Watson (55), the presence of any kind of oil in the tracheae is ultimately fatal. He shows, however, that survival time may vary from a few minutes to a week, depending on the toxicity and the amount of oil taken into the tracheal system. This amount varies with the number of times the larva contacts the oil film. 

The site of hydrocarbon pheromone production in the nitidulid beetles has been identified as very large, round abdominal cells, connected to the tracheal system by fine ducts (Dowd and Bartelt, 1993 Nardi et al., 1996). The secretory cells contain several lipid spheres (presumably pheromone and pheromone precursors), and are dramatically larger in beetles that are actively emitting pheromone (Nardi et al., 1996). Pheromone apparently diffuses from the cells,... 

Consideration of the waterproofing function of cuticular lipids first requires an assessment of cuticular transpiration relative to the overall water budget. The fact that organismal water-loss rates increase greatly when surface lipids are removed does not necessarily mean that increased cuticular permeability is responsible. Insects can lose water by transpiration through the cuticle, by evaporation from the tracheal system through open spiracles, and by... 

Closely linked to its extraordinary solvent capacities is water s role in transporting dissolved materials throughout the organism. With the exception of air-filled channels like the tracheal systems of insects, most of the transport processes of organisms involve movement of dissolved solutes. Diffusion of solutes within water is rapid, as is the translational and rotational movement of water itself. The extensive networks of hydrogen bonds that form among water molecules and between water and solutes do not impede this dynamic move-... 

There is another theory, also supported by experimental evidence, that a contact insecticide spreads laterally within the integument and then reaches the site of toxic action via the integument of the tracheal system (Gerolt, 1969). This mode of entry, also known as lateral transport, does not involve the hemolymph as carrier. 

Occurrence of hemocyanin related proteins in organisms. While textbooks teU that Hes occm only in arthropods and molluscs, recently Hes were also found in other phyla. The velvet worms (Onychophora) are considered living fossils and are closely related to the Euarthropoda. Onychophora possess a tracheal system for respiratory function, thus oxygen transport proteins have been considered unnecessary. In the hemolymph of the Epiperipatus sp. (Onychophora Peripatidae), an arthropod-type hemocyanin was found, demonstrating that such proteins exist outside the Euarthropoda. ... 

So far so good, but there is one problem with this line of reasoning the tracheal system may be primitive, but it is far from inefficient — with... 

The reason the tracheal system is so efficient is that oxygen remains in the gas phase, where it can diffuse rapidly, and need not pass into solution until the last possible moment, as it enters the flight muscle cells themselves. As a result, the ability of the tracheal system to deliver oxygen typically exceeds the capacity of the tissues to consume it. The only real inefficiency is the blind endings of the trachea, which branch into fine tubules in much the same way as the blind bronchioles in our own lungs. Just as we suffocate if we cannot physically draw breath, so too insects are limited by the diffusion of gases in the blind alleys of the tracheal system. Most insects get around this difficulty, as we do ourselves, by actively ventilating their trachea. 

Glazer, L. Shilo, B.Z. The Drosophila FGF-R homolog is expressed in the embryonic tracheal system and appears to be required for directed tracheal cell extension. Genes Dev., 5, 697-705 (1991)... 

As crb null mutants show severe developmental defects of the tracheal system and other ectodermal tissues (Tepass and Knust, 1990), we tested tracheal sp>ecific crb knockdown embryos for Che localization in tracheal cells. In Drosophila, organ sp>ecific expression experiments can be performed by the use of the UAS-GAL4 system (Brand and Perrimon, 1993). 

Beitel, G. Krasnow, M. A. (2000). Genetic control of epithelial tube size in the Drosophila tracheal system. Development 127,3271-3282. 

Casanova, J. (2007). The emergence of shape notions from the study of the Drosophila tracheal system. EMB O Rep. 8, 335-339. 

Gervais, L. Casanova, J. (2011). The Drosophila homologue of SRF acts as a boosting mechanism to sustain FGF-induced terminal branching in the tracheal system Development 138,1269-1274. 

Llimargas, M., Strigini, M., Katidou, M., Karagogeos, D. Casanova, J. (2004). Lachesin is a component of a septate jimction-based mechanism that controls tube size and epithelial integrity in the Drosophila tracheal system. Development 131,181-190. 

Wigglesworth VB. Growth and regeneration in the tracheal system of an insect, Rhodnius prolixus (Hemiptera). Q J Microscopical Science 1954 95 115-137. 

Locke M. The co-ordination of growth in the tracheal system of insects. Q J Microscopical Science 1958 99 373-391. 

Figure A2.10. Dorsal and ventral views of the tracheal system in third-instar larvae. (Redrawn, with permission, from Whitten 1957 [ Company of Biologists, Ltd.].)...

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