Cuttlefish Chameleons, Papuan Cuttlefish
Cuttlefish are often referred to as the 'chameleons of the sea'. Like other cephalopods such as squid and octopuses, they have a remarkable capacity to rapidly alter their skin colour. This assists them to evade predators by camouflaging themselves and also to communicate with other cuttlefish. This amazing ability for colour change is accomplished with the aid of special cells such as chromatophores and iridophores. There may be up to 200 of these specialised pigment cells per square millimetre. Chromatophores have small, elastic, pigment sacs and lie directly beneath the skin of the cuttlefish. Muscle contraction and relaxation by the animal can cause the skin pigment surface area to increase or decrease. The chromatophores are neurally controlled and thus can rapidly change allowing some species to produce complex patterns such as the flashing zebra stripes observed in aggressive male cuttlefish.
While chromatophores are responsible for red, yellow, brown and black colours, iridophores are reflective cell layers beneath the chromatophores that can cause the metallic green, blue, silver or gold patterns seen in some species. Iridophores also assist in concealment and communication, but are slower than the neurally controlled pattern changes generated by chromatophores. Some studies suggest that iridophore-generated colours may result from alterations in hormone levels.
Deepwater species can also employ another group of cells called photophores. These cells produce bioluminescence which can assist in prey attraction. However, photophores are often absent in shallow water species. These cuttlefish 'chameleons' generally utilise both chromatophores and iridophores to produce intense colour combinations and a spectacular diversity of patterns.
The Papuan Cuttlefish is found throughout tropical Australia, extending into northern NSW, and a wider distribution into the Indo-Malay Archipelago and Philippines.
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