On leucophores and the chromatic unit of Octopus vulgaris

The leucophores of Octopus vulgaris are much branched cells bearing, all over the surface, small clubs that contain electron-dense material of an unknown nature. Some tens of leucophores are organized to form a “sponge” in the centre of the chromatic unit, which can be elevated above the peripheral region. This central region reflects light over a broad band and may be important in camouflage. The chromatic unit also contains iridophores and chromatophores. The latter may be yellow, orange, red or black, and the different types are interspersed among one another in a regular manner. The chromatophores are disposed in a precise way with respect to the leucophores, the black ones lying above holes in the sponge. The possible significance of this arrangement for camouflage is discussed.