60.2 MB (60.0 MB compressed)
5616 x 3744 pixels
47.5 x 31.8 cm ⏐ 18.7 x 12.5 in (300dpi)
DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Caterpillar spiracle. Polarised light micrograph of part of the skin of a caterpillar, showing an air hole (spiracle, dark oval, lower right) leading to a breathing tube (trachea, orange) and the tracheal system. From each spiracle other trachea radiate out and branch to the surrounding tissue. The spiracles have muscles (brown bands on either side of the hole) to open and close them to prevent water loss. The tracheae, which are supported by chitinous rings, branch into finer and finer tubes and allow oxygen to diffuse to the tissues, and carbon dioxide to diffuse away from the tissues. Magnification: x36 when printed at 10 centimetres across.
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