melanosome

noun

me·​la·​no·​some mə-ˈla-nə-ˌsōm 

ˈme-lə-nə-

plural melanosomes

: one of the membrane-bound spherical to elliptical granules within a melanocyte (as in skin, eyes, or hair follicles) that functions in the synthesis, storage, and transport of melanin and that transfer melanin from melanocytes to keratinocytes in skin and hair shafts

The melanin emerges from the cells in tiny cucumberlike particles called melanosomes that rise through a branching network of tubelike connections, eventually to board the keratinocytes rising from the basal-cell layer to the outer keratin layer.

—James C. G. Conniff

also : a similar melanin-producing granule in a melanophore

In contrast to mammalian melanosomes, the melanosomes in fish and amphibian melanophores, which are equivalent to the melanocytes in mammals, are rapidly transported bidirectionally in response to extracellular stimuli and are not transferred to neighboring cells.

—M. Fukada

Examples of melanosome in a Sentence

Recent Examples on the Web

In 2010, Benton’s lab published a study describing how to ascribe color to different dinosaurs by looking at the shapes of different melanosomes. —Sofia Quaglia, Discover Magazine, 27 Apr. 2023

The second 2016 study concluded that Tully should be grouped with vertebrates because the pigment granules in the eyes, called melanosomes, were arranged by shape and size much like vertebrate eyes. —Jennifer Ouellette, Ars Technica, 25 Apr. 2023

The iridescence arises from the packing of the melanosomes within the feather. —Jakob Vinther, Scientific American, 1 Mar. 2017

One source of colors in animals is a cellular structure called a melanosome. —Carl Zimmer, Discover Magazine, 24 Jan. 2012

But until now, little work has been done to characterize the chemistry of the pigment in these fossil melanosomes and there is little evidence to prove that the melanosome shape actually reflects the original color in fossils. —Jakob Vinther, Discover Magazine, 5 Oct. 2015

Paleontologists have recently questioned earlier hypotheses about which melanosome shapes create which particular shades. —Riley Black, Scientific American, 20 Apr. 2022

This study is the first time different melanosome shapes have been found in a pterosaur, suggesting both a genetic link to birds and that the feathers on the pterosaur were multicolored. —NBC News, 20 Apr. 2022

Niacinamide, a form of vitamin B3, inhibits melanosome transfer (with melanin) to skin cells. —Dori Price, Good Housekeeping, 23 Mar. 2021

Word History

Etymology

melano- + -some entry 3

First Known Use

1961, in the meaning defined above

Medical Definition

melanosome

noun

me·​la·​no·​some mə-ˈlan-ə-ˌsōm, ˈmel-ə-nō- 

: one of the membrane-bound spherical to elliptical granules within a melanocyte (as in skin, eyes, or hair follicles) that functions in the synthesis, storage, and transport of melanin and that transfer melanin from melanocytes to keratinocytes in skin and hair shafts

The size and shape of eumelanin particles in the body depend on the size and shape of the melanosomes, the organelles in melanocytes that synthesize melanin.

—Corinna Wu, Science News

also : a similar melanin-producing granule in a melanophore