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Horn Sharks. Heterodontidae species.

horn shark portjackson shark Heterodontus portusjacksoni bullhead

All text on this page is copyright protected: © 2002 Kelvin Aitken.
All rights reserved. Students may use this information for personal research only. Not for commercial use.

Order: Heterodontiformes
Family: Heterodontidae
Genus: Alopias
Species: pelagicus
Taxonomic name (of species shown above): Heterodontus portusjacksoni
Other Common Names: Bullhead Shark, Port Jackson Shark, Horn Shark.

Probably the most well known of the eight species of Horn Shark is the Port Jackson Shark (Heterodontus portusjacksoni), named after a bay in eastern Australia. Port Jackson Sharks are one of the most common sharks seen in southern Australian waters, especially in New South Wales. This species ranges from southern Queensland around the southern States to Geraldton in Western Australia. Port Jacksons have a distinctive bulky, blunt head with a "pursed" mouth. They are usually grey in colour with tints of brown or green, and a black-banded pattern on the body similar in shape to the harness worn by a seeing-eye dog.

Female Port Jackson sharks may travel as far as 850 km to lay their eggs among shallow rocky reefs during late winter and spring. These spiral-shaped eggs are a dark green or brown when new but soon become almost black and are usually encrusted with spots of algae. Females are supposed to push their eggs into crevices but they are wedged in by wave action. Eggs that have been left in the open or torn loose by storms are often found washed ashore. The young pups that hatch 10–12 months later are about 15–20 cm long at first but they grow to 1.5 m or more.

Divers and snorkelers may come across Port Jackson Sharks, sometimes in groups of 10–20, lying in sheltered caves or gullies on shallow rocky reefs during the day. Here they sleep or rest until the night when they disperse to feed on sea urchins and shells. Their scientific name, Heterodontus, means 'different teeth' and refers to their spiky front teeth, which are ideal for prying and holding; the fused teeth-plates at the rear are perfectly developed for crushing shelled molluscs.

Crested Horn Sharks (Heterodontus galeatus) are only found on the east coast of Australia in a confined region from southern Queensland to Montague Island. Similarities with the Port Jackson are their teeth, diet and body shape. They can be best distinguished from the Port Jackson shark by the larger crests above the eye and the lack of a harness-shaped pattern on the body, having two indistinct dark bands or 'saddles' over a yellowish brown base colour instead. They also have rounder dorsal fins and do not congregate in groups.

Reproductive behaviour is very different from that of the Port Jackson Shark. Females lay spiral-shaped egg cases with long sticky tendrils up to 2 m long. The female chooses a section of reef, often where other females have already deposited their eggs, and tightly circle a suitable vertical projection, such as sea tulips, kelp or a rock. As she rubs her body against the reef the sticky tendrils, which have emerged slightly from her body, become attached, pulling out the egg cases as she swims away. The eggs are anchored to the reef by the well-tangled tendrils. Eight months later the 20–22 cm young emerge to grow to their adult size of 1.5 m

The Zebra Horn Shark (Heterodontus zebra) is found in the Indo-Pacific being more common in Asian seas. Their name comes from the striking pattern of dark vertical stripes on a pale background.

Other species of Horn Shark include the Californian Horn Shark (Heterodontus californicus) and the Mexican Horn Shark (Heterodontus mexicanus)

Horn sharks can be sent into a state of trance-like ecstasy by gently scratching their bellies and throats. However these docile sharks should not be handled as their robust dorsal spines can inflict a painful wound and their crushing teeth can mash a wayward finger.