Heterodontus portusjacksoni

Geographic Range

Heterodontus portusjacksoni is one of the better known species of horn sharks ( Heterodontus ). It was named after Port Jackson in Sydney Harbour. They are found from southern coastal Australia to the central coast of Western Australia. Some have been found as far north as York Sound in Western Australia. According to studies of the genetics of the Port Jackson sharks, there are two different populations found in different regions that extend the length of the southern part of Australia.

• Biogeographic Regions
• australian australian
  • native native
• pacific ocean pacific ocean
  • native native

Habitat

Port Jackson sharks live in tropical marine waters usually near the bottom of rocky environments. They tend to be found in caves with sandy bottoms. They are nocturnal, bottom-dwelling sharks and are commonly found in depths of 100 meters, but have been found up to 275 meters. Some have been found in muddy areas with sea grass.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• coastal coastal

Physical Description

Port Jackson sharks are the largest in the genus Heterodontus . At birth, they are 23 to 24 cm. Females are usually larger as these sharks mature. At adolescence, males are between 50 and 80 cm, whereas females range between 64 and 83 cm. The difference between females and males is seen when fully mature, when females can measure more than 123 cm and males more than 105 cm.

Their color is gray to light brown. They have a dark spot on their nose with a black bar running the length of their face as wide as the eye. There are black stripes that flow along the body, giving them the appearance of wearing a harness.

Port Jackson sharks have two dorsal fins with a spine at the tip. These are not venomous and can be very sharp when young, but usually dull with age. The spines can be found washed up on shores and are believed to be the origin for the name of the “horn sharks”.

Port Jackson sharks have two types of teeth: incisors for cutting and molars for crushing. They are ideal for holding, crushing, and breaking the shells of their crustacean and mollusk prey.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger

Development

Port Jackson sharks deposit their egg cases and then wedge them into rock crevices. The eggs develop into juvenile sharks in the egg case and then emerge after 10 to 12 months. After the young sharks are born, they move into nursery areas in bays and estuaries where they remain until maturity. Juvenile Port Jackson sharks remain in mixed sex groups for several years. After a few years, the young move into deeper waters and separate into female and male groups.

Reproduction

Mature female Port Jackson sharks move to inshore reefs accompanied by some males beginning in July and August. They mate on coastal reefs and of the coast of New South Wales. Many males do not participate in breeding and remain in deeper water offshore. Breeding sharks congregate in caves but little is known about courtship and pair formation.

Port Jackson sharks are oviparous. During August and September, females lay 10 to 16 eggs in shallow reefs at depths of 5 to 30 meters. The egg cases are brown, spiraled structures that the females wedge into rock crevices. Females will hold an egg case in their mouth and insert it into a safe crevice. Females usually use the same breeding sites each year. Port Jackson sharks have been seen eating their own egg cases, but they have never been seen breeding. The young hatch out of the egg case after 10 to 12 months.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Once the female has layed her eggs, along with a supply of nutrients in the yolk sac, and placed them in safe rock crevices to develop, there is no further parental involvement.

• Parental Investment
• no parental involvement
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • protecting
    • female

Lifespan/Longevity

No information on lifespan was found for Port Jackson sharks.

Behavior

Port Jackson sharks segregate into same-sex groups. Males and females may occupy different habitats during most parts of the year. Males and females encounter each other only briefly during breeding. Port Jackson sharks are mainly active at night, when their prey are active, and rest in crevices and under rock outcroppings during the day.

• Key Behaviors
• natatorial natatorial
• nocturnal nocturnal
• motile motile
• migratory migratory
• social social

Home Range

These sharks shows a pattern of migration southwards after breeding, moving up to 850 km north of breeding reefs before returning to the same sites the next year. Some may range as far south as Tasmania from the Sydney area in New South Wales in their migration. It is thought that migrating adult Port Jackson sharks move northwards along inshore coastal waters but return to their breeding reefs along deeper offshore waters.

Communication and Perception

Port Jackson sharks, like other sharks, probably have keen chemosensation and can detect small movements in the water with tactile organs. Nothing is known about communication in these sharks.

• Perception Channels
• tactile tactile
• chemical chemical

Food Habits

Port Jackson sharks feed primarily on invertebrates, mainly echinoderms . They eat sea urchins , starfish , polychaetes , large gastropods , prawns, crabs, barnacles , and small fishes. Juveniles, with their smaller, more pointed teeth, apparently take more soft-bodied prey than adults. Food items in stomachs are usually broken into small pieces, which show how the powerful molar-like teeth grind the food. Food is apparently taken at night on the ocean bottom. Juveniles dig food out of the sand by sucking in water and sand and blowing it out of the gill covers.

Respiration can occur by pumping water into the first of the enlarged gill slits and out the last four, which is thought to allow the shark to crush and grind its prey at leisure without having to take in water through its mouth and risk food leaving the gill slits.

• Primary Diet
• carnivore carnivore
  • eats non-insect arthropods
  • molluscivore molluscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans
• echinoderms
• other marine invertebrates

Predation

The adults seem to be well protected by their sedentary habits, cryptic coloration, nocturnal behavior, fin spines, and disruptive color patterns. Some predators are large sharks such as great white sharks ( Carcharodon carcharias ) as well as sea lions ( Otariidae ). Juveniles in nursery grounds are more vulnerable to predation by other sharks. Eggs may be eaten by male Port Jackson sharks.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

There are several known parasites of Port Jackson sharks, including parasitic isopods . Port Jackson sharks are important predators of echinoderms and crustaceans. Through predation on echinoderms it is likely that they positively influence populations of mollusks and algae.

Economic Importance for Humans: Positive

Port Jackson sharks are important members of healthy marine ecosystems.

Economic Importance for Humans: Negative

Port Jackson sharks are considered harmless to people.

Conservation Status

Port Jackson sharks are not considered threatened currently.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Jace Hopper (author), University of Notre Dame, Karen Powers (editor, instructor), Radford University.

References

Budker, P. 1971. The Life of Sharks . New York: Columbia University Press.

McGrouther, M. 2005. "Port Jackson Shark, Heterodontus portjacksoni" (On-line). Fishes: Australian Museum Fish Site. Accessed March 06, 2006 at http://www.amonline.net.au/fishes/students/focus/heter.htm .

Rogers, C. 2000. Port Jackson Sharks. Nature Australia , 10: 26-33.

Whitley, G. 1940. The Fishes of Australia . Sydney: Royal Zoological Society N.S.W..