Меланосома: Пігменттің құрылысы, қазба жәндіктердің түсі және эволюциялық маңызы

Organelle found in animal cells used for the synthesis, storage and transport of melanin
the geological term

A melanosome is an organelle found in animal cells and is the site for synthesis, storage and transport of melanin, the most common light absorbing pigment found in the animal kingdom. Melanosomes are responsible for color and photoprotection in animal cells and tissues. Melanosomes are synthesised in the skin in melanocyte cells, as well as the eye in choroidal melanocytes and retinal pigment epithelial (RPE) cells. In lower vertebrates, they are found in melanophores or chromatophores.

Melanosomes are relatively large organelles, measuring up to 500 nm in diameter. Recently, melanosomes were found in spiders as well. The beautiful and rapid colour changes seen in many cephalopods such as octopuses and squid, are based on a different system, the chromatophore organ.

Recent (2008) discoveries by Xu Xing, a Chinese paleontologist, include fossilized feathers in rock formations dating from the Jurassic period (200 to 150 million years ago) to the late Paleogene and Neogene periods (66 to 2 million years ago). The feathers contain preserved residues of carbon that were previously thought to be traces of bacteria that decomposed feather tissues; however these (residues) are in fact microscopic organic imprints of fossilized melanosomes. Some of these structures still maintain an iridescent color typical of feather and fur tissues. It is conjectured that these microscopic structures could be further studied to reveal the original colors and textures of softer tissues in fossils. "The discovery of ultra structural detail in feather fossils opens up remarkable possibilities for the investigation of other features in soft bodied fossils, like fur and even internal organs," said Derek Briggs of the Yale University study team. Melanosomes were used to discover the true colors of fossil Anchiornis huxleyi by a collaborative team including members from the Beijing Museum of Natural History, Peking University, Yale University, the Peabody Museum of Natural History, the University of Akron, and the University of Texas at Austin. Melanosomes have also been found in fossils from Tupandactylus cf. imperator pteurosaurs in the Lower Cretaceous Crato Formation, in the Araripe Basin, in Brazil.

Melanosomes are believed to template melanin polymerization by way of amyloidogenesis of the protein Pmel17, which is present in abundant quantities in melanosomes.