Spider are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration. Bilins are found, for example, in "Micrommata virescens", resulting in its green color. Guanine is responsible for the white markings of the European garden spider "Araneus diadematus". It is in many species accumulated in specialized cells called guanocytes. In genera such as "Tetragnatha", "Leucauge", "Argyrodes" or "Theridiosoma", guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors
European perch European perch Perca fluviatilis, commonly known as the European perch, perch, redfin perch, big-scaled redfin, English perch, Eurasian perch, Eurasian river perch or common perch, is a predatory species of perch found in Europe and northern Asia. The species is a popular quarry for anglers, and has been widely introduced beyond its native area, into Australia, New Zealand, and South Africa. They have caused substantial damage to native fish populations in Australia and have been proclaimed a noxious species in New South Wales. European perch are greenish with red pelvic, anal and caudal fins. They have five to eight dark