Port Jackson shark

Port Jackson shark

Order: Heterodontiformes | Family: Heterodontidae

Heterodontus portusjacksoni

It is one of the three species of the genus Heterodontus inhabiting the waters of Australia. This cartilaginous fish can be found in the southern part of Australia, from Queensland through Tasmania to New South Wales. It also occurs in the coastal waters of Port Jackson, from which its name stems. It is a demersal fish, which means that it stays close to the ocean’s bottom. Its usual dwelling is a rocky base. It can also be found on sandy or muddy bases and in underwater meadows at depths from 1-2 to 100 m, although its presence has also been noted at 275 m deep. It is an average-sized shark, reaching a length of 5 feet 5 inches.

Adults live in small groups, whereas juveniles are loners. It gets very used to its place of sleep and uses caves and rocky outcrops around that place as protection during the day. It is active at night when it hunts mollusks, sea urchins, crustaceans, and fish. Black sea urchins from the species Centrostephanus rodgersii are often its prey. This shark gets its sustenance mainly by sucking in water and sand from the bottom, where subsequently the sand is blown out of the gill slits, and the food is retained in its mouth. Digestion of food can take a long time. The food is transported from the mouth to the stomach, where it is stored and preliminarily digested. Any type of unwanted food is spit out.

This shark has the ability to turn its stomach inside out and spit it out of its mouth to get rid of any unwanted contents.

One of the characteristics of the Port Jackson shark is its different teeth located in its big, blunt head with prominent crests above its eyes. Front teeth are small, sharp, and pointed, whereas the back teeth are flat and blunt. They are used for holding, breaking, and later crushing and grinding the shells of mollusks and echinoderms. Juveniles have sharper teeth, and their diet is comprised mainly of soft food. Another characteristic is its coloration. It has a gray-brown body with dark brown markings that look like a harness. These markings go from the eye socket to the first dorsal fin, and then on the sides to the pelvic fins. Spikes that can be found at the base of its dorsal fins are also distinctive. These spikes are probably poisonous. Its small mouth and nostrils that are connected to the mouth are also distinguishable.

This shark can cover from 600 to 800 kilometers during its yearly travels to the south in the summer and to the north in the winter. It ends its migration in coastal pools in order to procreate. Males arrive first, whereas females leave these pools later, maybe to lower the predation on freshly laid eggs. Breeding begins in August and lasts till the middle of November. The female lays pairs of eggs every 11 to 14 days, which makes the overall amount of eggs between 10 and 16, but the average is between 10 and 12. The egg capsules have the shape of a screw. The female puts them in her mouth and locates them in rocky crevices in shallow uncovered reefs at the depth of between 1 and 5 m. The incubation takes around 11 months. The mortality rate of eggs is very high, at around 89%. After hatching the young feed on nutrients from the gall bladder for some time. Males reach sexual maturity between ages 8 and 10, whereas females at 11 to 14.

Why doesn’t the Port Jackson shark have to be in constant motion to breathe?

The Port Jackson shark can eat and breathe at the same time. It is an extraordinary ability when it comes to sharks, because a lot of them have to swim with their mouths wide open to force water over the gills. This shark can pump water into the first enlarged gill slit and out through the other four gill slits. By pumping water across the gills, the shark does not need to move to breathe. It can lie on the bottom for long periods of time.

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