### Identification The Aplysia concava, or the Concave Sea Hare, is a master of cryptic coloration. Typically reaching lengths of 8 to 12 cm, its soft, plump body is a mottled tapestry of olive greens, earthy browns, and sandy creams—perfectly mimicking the algae-covered rocks of its home. Look closely at its head for the two pairs of prominent tentacles: the lower oral tentacles and the upper, rabbit-ear-like rhinophores used for "smelling" the water. Unlike the larger Spotted Sea Hare, *A. concava* lacks distinct black rings; instead, it features a characteristic "concave" internal shell (partially visible through a slit in the mantle) and sweeping, wing-like parapodia that it uses to undulate gracefully through the water column.
### Habitat & Range This species is a gem of the South-western Pacific, most frequently encountered along the temperate coastlines of Australia and New Zealand. It is a specialist of the intertidal and shallow subtidal zones. You’ll find it tucked into crevices of rocky reefs or navigating the swaying blades of seagrass meadows (*Zostera*). They prefer sheltered bays and lagoons where the surge is minimal, allowing them to graze undisturbed by heavy surf.
### Behaviour Observing a "slug" might sound dull, but the social life of *A. concava* is fascinating. They are simultaneous hermaphrodites, often forming spectacular "mating chains" where three or more individuals stack together, each acting as a male to the one below and a female to the one above. When spooked, they don't just flee; they deploy a dual-layered chemical defense, releasing a cloud of vibrant purple ink and a sticky white secretion called opaline to baffle the senses of would-be predators.
### Diet These are the dedicated gardeners of the reef. They are strict herbivores, using a tooth-lined tongue called a radula to rasp away at red and green macroalgae. Interestingly, their diet dictates their appearance; the pigments from the seaweed they consume are sequestered into their skin, providing a dynamic camouflage that changes as they move from one "pasture" to the next.
### Fascinating Fact The purple ink of the sea hare isn't just a visual smokescreen—it’s a chemical decoy! The ink contains high concentrations of amino acids that trick a predator’s chemosensors into thinking they’ve hit a massive cloud of food. While the confused fish "attacks" the phantom ink, the sea hare makes its slow, silent getaway.