This list of molluscs of the Houtman Abrolhos includes 492 species of marine molluscs which have been recorded from the waters of the Houtman Abrolhos, an island group in the Indian Ocean off the coast of Western Australia.
These molluscs are predominantly gastropods (346 species, 70%) and bivalves (124, 25%); the remaining 5% of species consist of cephalopods (14 species), chitons (5 species) and scaphopods (4 species).
About two thirds of the species have a tropical distribution, temperate species account for 20%, and the remaining 11% are endemic to Western Australia.
A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishermen sometimes call cephalopods "inkfish," referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
The Houtman Abrolhos is a chain of 122 islands, and associated coral reefs, in the Indian Ocean off the west coast of Australia, about eighty kilometres (50 mi) west of Geraldton, Western Australia. It is the southernmost true coral reef in the Indian Ocean, and one of the highest latitude reef systems in the world. It is one of the world's most important seabird breeding sites, and is the centre of Western Australia's largest single-species fishery, the western rock lobster fishery. It has a small seasonal population of fishermen, and a limited number of tourists are permitted for day trips, but most of the land area is off limits as conservation habitat. It is well known as the site of numerous shipwrecks, the most famous being the Dutch ships Batavia, which was wrecked in 1629, and Zeewijk, wrecked in 1727.
Blue-ringed octopuses, comprising the genus Hapalochlaena, are four highly venomous species of octopus that are found in tide pools and coral reefs in the Pacific and Indian oceans, from Japan to Australia. They can be identified by their yellowish skin and characteristic blue and black rings that change color dramatically when the animal is threatened. They eat small crustaceans, including crabs, hermit crabs, shrimp, and other small sea animals.
The blue-lined octopus is one of four species of highly venomous blue-ringed octopuses. It can be found in Pacific Ocean waters that stretch all the way from Australia to Japan. It is most commonly found around intertidal rocky shores and coastal waters to a depth of 15 metres (49 ft) between southern Queensland and southern New South Wales. It is relatively small, with a mantle up to 45 millimetres (1.8 in) in length. In its relaxed state, it is a mottled yellow-brown with dark blue or black streaks covering the whole body apart from the underside of its arms, but its vibrant blue markings appear as a warning to predators when they feel threatened. Along with its other closely related species, the blue-lined octopus is regarded as one of the most dangerous animals in the sea, and its venom can be fatal to humans.
Panulirus cygnus is a species of spiny lobster, found off the west coast of Australia. Panulirus cygnus is the basis of Australia's most valuable fishery, making up 20% of value of Australia's total fishing industry, and is identified as the western rock lobster.
The Leeuwin Current is a warm ocean current which flows southwards near the western coast of Australia. It rounds Cape Leeuwin to enter the waters south of Australia where its influence extends as far as Tasmania.
North Island is the northernmost island in the Houtman Abrolhos, a coral reef archipelago in the Indian Ocean off the coast of Mid West Western Australia. Located about 14 km (9 mi) from the nearest island group, it is one of the largest islands in the Houtman Abrolhos, and one of the few to support dune systems. It has relatively diverse flora dominated by chenopod shrubs and fauna that includes the introduced tammar wallaby, around seven species of reptile, and about 15 resident bird species.
Melo miltonis, the southern bailer or southern baler, is a large sea snail, a marine gastropod mollusc in the family Volutidae, the volutes.
The Percy Sladen Trust Expeditions to the Abrolhos Islands were two scientific expeditions, conducted in 1913 and 1915 under the leadership of Professor William John Dakin and funded by the Percy Sladen Trust. These expeditions conducted extensive research into the natural history of the Houtman Abrolhos, an archipelago in the Indian Ocean off the coast of Western Australia.
Cuttlefish or cuttles are marine molluscs of the order Sepiida. They belong to the class Cephalopoda, which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique internal shell, the cuttlebone, which is used for control of buoyancy.
Cephalopod fins, sometimes known as wings, are paired flap-like locomotory appendages. They are found in ten-limbed cephalopods as well as in the eight-limbed cirrate octopuses and vampire squid. Many extinct cephalopod groups also possessed fins. Nautiluses and the more familiar incirrate octopuses lack swimming fins. An extreme development of the cephalopod fin is seen in the bigfin squid of the family Magnapinnidae.