Sepia mestus, also known as the reaper cuttlefish or red cuttlefish, is a species of cuttlefish native to the southwestern Pacific Ocean, specifically Escape Reef off Queensland (15°47′S 145°47′E / 15.783°S 145.783°E / -15.783; 145.783) to Murrays Beach off Jervis Bay (35°08′S 150°46′E / 35.133°S 150.767°E / -35.133; 150.767). Reports of this species from China and Vietnam are now known to be misidentifications. S. mestus lives at a depth of between 0 and 22 m.
Sepia mestus exhibits sexual dimorphism. Females grow to a mantle length (ML) of 124 mm, while males do not exceed 77 mm ML.
The type specimen was collected off the Australian coast and is deposited at The Natural History Museum in London.
Sepia mestus is endemic to Australia (Reid et al. 2005), ranging along the east coast from northern Queensland to Jervis Bay in New South Wales (Reid et al. 2005).
Sepia mestus lives in depths up to 22 m. inhabiting a tropical climate
Sepia mestus typically lives on rocky reefs and is typically seen under ledges (Norman 2003).
Many of the world's cuttlefish species are found in Australian waters, including S. mestus.
Camouflage is a distinctive feature of Cephalopods including S. mestus. Camouflage is achieved through changing of the animals colour and texture. Small organs in the skin allow called chromatophores allow for colour change. These chromatophores can be described as very small bags of dense pigment that can be expanded or contracted in which a spot of particular colour can be displayed.
Sepia mestus and most other species of cuttlefish can alter skin texture to blend in with their environment. This is achieved by pushing up flaps of skin to match shapes of rock, coral, and seaweed. These flaps are known as papillae. Contracting rings of muscle around the base of these papillae allows for the flaps to rise, changing the appearance of the animal.
Sepia mestus can also bury itself under the sand to avoid predators.
Increasing levels of carbon dioxide in the atmosphere causes ocean acidification and is potentially a threat to all cuttlefish. According to studies, high CO2 concentrations, cuttlefishes tend to lay down a denser cuttlebone. This could negatively affect cuttlefish buoyancy regulation (Gutowska et al. 2010).
It is considered of least concern.
