Heterodontus portusjacksoni

The Port Jackson shark (Heterodontus portusjacksoni) is a nocturnal, oviparous (egg laying) type of bullhead shark of the family Heterodontidae, found in the coastal region of southern Australia, including the waters off Port Jackson. It has a large, blunt head with prominent forehead ridges and dark brown harness-like markings on a lighter grey-brown body, and can grow up to 1.65 metres (5.5 ft) long. The Port Jackson shark is a migratory species, traveling south in the summer and returning north to breed in the winter. It feeds on hard-shelled mollusks, crustaceans, sea urchins, and fish. Identification of this species is very easy due to the pattern of harness-like markings that cross the eyes, run along the back to the first dorsal fin, then cross the side of the body, in addition to the spine in front of both dorsal fins. The Port Jackson shark is endemic to the temperate waters around southern Australia and can be found in an area stretching from southern Queensland, south to Tasmania, and west to the central coast of Western Australia. Dubious reports exist of catchings as far north as Western Australia's York Sound. A single specimen of this species was collected in a set net at Makara, Wellington in 1954. Two more specimens reported as being from New Zealand were presented to the British Museum however although these two specimens have been located they have no information on their collection location to confirm this assertion. and on one occasion, it has occurred off the coast of New Zealand. Genetic studies suggest two Australian groups, one found from Northeastern Victoria to Western Australia and the second found from Southern Queensland to New South Wales. The species is believed to have originated somewhere off the coast of South Africa. It usually lives at depths of less than 100 metres (330 ft), but has been known to go as deep as 275 metres (902 ft). The shark's territory is habitually on or near the sea bottom, which is also its feeding area. Rocky environments are the most common habitat, though sandy and muddy ones, as well as seagrass beds, are sometimes used. During the day, when it is usually not active, it can be found in flat areas which offer some shelter from currents (including caves) or near other sheltering positions such as rocky outcrops. Port Jackson sharks can grow up to 1.65 metres (5.5 ft) long and are similar to others of their genus, bearing a broad, blunt, flat head, an anal fin, and crests above its eyes. However, the species possesses characteristics that make them easily identifiable, such as their teeth and the harness-like markings which run for a majority of their body length. These markings run from their eyes to their first dorsal fin and then across the rest of their bodies. Both dorsal fins are close to equal size, each with a spine at the foremost edge. These spines are rumored to be poisonous. Other features that help distinguish them are their small mouths as well as their nostrils, which are connected to their mouths. The sharks have grey-brown bodies covered by black banding, which covers a large portion of their sides and backs. One of these bands winds over the face and progresses to the shark's eyes. Another harness-shaped band goes around the back, continuing to the pectoral fins and sides. Thin, dark stripes are also present on the backs of Port Jackson sharks. These progress from the caudal fin to the first dorsal fin. The teeth of the Port Jackson shark are one of its most distinguishable features. Unlike other sharks, its teeth are different in the front and back. The front teeth are small, sharp and pointed, while the back teeth are flat and blunt. These teeth function to hold, break then crush and grind the shells of the mollusks and echinoderms upon which this species feeds. Juveniles of the species have sharper teeth and their diet has a higher proportion of soft-bodied prey than adults. The Port Jackson shark has five gills, the first supports only a single row of gill filaments, while the remaining four support double rows of filaments. Each of the second to the fifth gill arches supports a sheet of muscular and connective tissue called a septum. The shark possesses behind each eye an accessory respiratory organ called a spiracle. Along the top and bottom of each gill filament are delicate, closely packed, transverse flaps of gill tissue known as secondary lamellae. It is these lamellae that are the actual sites of gas exchange. Each lamella is equipped with tiny arteries that carry blood in a direction opposite to that of the water flowing over them. To compensate for the relatively low concentration of dissolved oxygen in seawater, water passes over the secondary lamellae of sharks some 5% as fast as air that remains in contact with the equivalent gas exchange sites, such as the alveoli of the lungs found in humans. This delay allows sufficient time for dissolved oxygen to diffuse into a shark's blood.