Hello finatics! This week’s featured species is an endemic species from Australia and is a member of one of the more primitive shark families. The Port Jackson shark (Heterodontus portusjacksoni) belongs to the family Heterodontidae, a family named for jaws filled with differing teeth forms, and resembles shark species that lived over 220 million years ago (Parker, 2008). The Port Jackson is a relatively small shark, reaching a maximum of 5.5 feet (1.7 m) (Huveneers, & Simpfendorfer, 2015). It has a blunt, pig-like snout with scrolling nostrils, distinctive eye ridges, and a unique harness pattern over its body (Parker, 2008; Ebert, Fowler, & Dando, 2015). They also pack a pair of sharp spines in front of their dorsal fins that aid in their defense against potential predators.
As I mentioned, members of Heterodontidae, which include the Port Jackson shark, the California horn shark (Heterodontus francisci), and other bullhead sharks, are named so for their specialized teeth (Tricas et al., 1997). In the front of their jaws they have small gripping teeth that are incredibly sharp. While the back of the jaw is made of moral, pavement-like teeth that are designed to crush the hard shells of crustaceans (Parker, 2008). I know most people are terrified of being bitten by a great white, but honestly these jaws scare me! Something about a body part being crushed like a walnut just creeps me out!
Port Jackson sharks have another quirky adaptation: they can eat and breathe at the same time. Most sharks have to either swallow or breathe, they cannot do both at the same time, however a trick in the Port Jackson shark’s anatomy allows them to be able to do both (Parker, 2008)! Sharks have 5 pairs of gill slits. These gill slits each have hundreds of feather-like filaments, which are each made of leaf-like branches called lamellae. The function of the lamellae are to create a large surface area for absorbing oxygen from the water as it flows over the gills. Inside the Port Jackson’s first pair of gill slits are a single row of filaments, while the remaining pairs of gill slits have two rows of filaments each. They also have an accessory spiracle, much like a stingray, just behind their eye. This allows the Port Jackson shark to pump water through the first pair of gill slits and out over the other four pairs. The spiracle helps keep keep the gills clear of debris when debris from the bottom is disturbed (Parker, 2008). This is an extremely useful adaptation for a shark that spends its day resting on the sea floor before venturing out at night to forage (Klimley, 2013).
aquatich (Videographer). (2011 October 14). Port Jackson Sharks, Heterodontus portusjacksoni [Video Clip]. Retrieved from https://www.youtube.com/
The Port Jackson shark is a “home body.” These sharks are known to favor particular reefs or caves, returning to a particular resting place every day (Tricas et al., 1997). During surveys, divers placed spaghetti-type tags on Port Jackson sharks inhabiting small caves near Bondi Reef near Sydney, Australia. The divers then returned over subsequent days and nights to find the same sharks at the same caves during the day, but found the caves empty at night, presumably while the sharks were out feeding (Klimley, 2013). However, these sharks are known to leave the comforts of home during the breeding season each year, migrating south during the summer and autumn months (O’Gower, & Nash, 1978). Even during these migrations, these sharks appear to have a home away from home, returning to the same reefs year after year to breed (Huveneers, & Simpfendorfer, 2015). After mating, the females lay corkscrew shaped egg cases in rocky crevices and fissures. A single female can lay up between 10 and 15 egg cases between August and October each year. With any luck, the eggs will hatch 10 to 11 months later (Rodda, & Seymour, 2008).
When the pups hatch from their egg cases, they are only a few inches long. They will spend their time close to their hatch site for their first few year until they reach sexual maturity and then they will begin the annual migrations during the breeding season with the adults (Huveneers & Simpfendorfer, 2015). Check out the end of this short video to see some absolutely adorable Port Jackson shark pups!
Abyss Scuba Diving (Videographer). (2017 September). Port Jackson Sharks of Sydney [Video Clip]. Retrieved from https://www.youtube.com/
We are just beginning to scratch the surface of understanding how changing climate is impacting elasmobranchs. A recent study questioned whether the rising temperatures would have an impact on brain development and function. To test this, researchers incubated Port Jackson egg cases while exposed to two different temperatures: a control group exposed to current ocean temperatures; and a test group exposed to elevated end-of-century projected temperatures. The team then measured the hatching’s preferential responses for left or right laterality brain function. The lateralization of brain function is the tendency for some neural functions or cognitive processes to be specialized to one side of the brain or the other. If you’ve ever taken a test to determine if you’re “right brained” or “left brained” (are you more artistic or scientific), this is the same type of thing. The sharks that were incubated at the elevated end-of-century temperatures demonstrated a stronger, absolute laterality and were significantly biases towards the right relative to their control counterparts (Vila Pouca, Gervais, Reed, & Brown, 2018). The researchers suggested that this strong laterality could be a coping mechanism to deleterious effects of climate change on the development of the brain (Vila Pouca, Gervais, Reed, & Brown, 2018). More research is needed into the potential impacts of climate change on elasmobranchs, but this is strong evidence that rising ocean temperatures could significantly impact the development of shark embryos.
I just have to share this because he makes me super happy and I hope he will make you happy to! My friend Helen went to Australia last summer as part of her graduate studies (be jealous, because I am!) and she was kind enough to bring me back a Port Jackson plushie! His name is Aussie and he is awesome.
Authority: Meyer, 1793
Family: Heterodontidae; 9 species
Length: Maximum of 5.5 feet (1.7 m)
Weight: 15 – 33 lbs (6.8 – 15 kg)
Habitat: Continental shelf, coastal reefs, rocky areas, and kelp beds
Depth: Surface to 902 feet (275 m)
Gestation: 10 – 11 incubation period before hatchlings leave egg case
Litter Range: 10 – 15 eggs laid per year
Home Range: Endemic to Australia (except northern Australia) and New Guinea; one independent sighting in New Zealand
Diet: Bottom dwelling crustaceans
IUCN Status: Least Concern
(Parker, 2008; Ebert, Fowler, & Dando, 2015; Huveneers & Simpfenforfer, 2015; Skomal, 2016)
Thanks so much for checking out the Port Jackson Shark! If you missed last week’s featured species, please be sure to check out the Southern Stingray, one of my favorite rays! If there is a species of shark you’d love to know more about, leave me a comment or send me a message! I would love to do a feature on your favorite species.
Exciting news!! I have joined the team of a non-profit organization, Reef Pup, as a conservation consultant and resident blogger. You can check out my weekly blog feature on Mondays at ReefPup.org! I cannot wait to share all the research, conservation, restoration, and of course TRAVEL we will be doing! And of course, I will always be here! So connect with me on Instagram and Facebook for even more elasmo fun!
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Conservation legislation needs public support in order to become law and help protect the environment and wildlife. Tell your representatives that you care about environmental and wildlife conservation. It only takes a moment to make a change that will last a lifetime. Until next time finactics!
Featured Image Source
McGee, P. (Photographer). (2018). Port Jackson Shark at Cabbage Tree Bay [Digital Image]. Retrieved from https://www.diveplanit.com/dpcontent/uploads/2018/05/Port-Jackson-Shark-2-Cabbage-Tree-Bay-by-Pete-McGee.jpg
Ebert, D. A., Fowler, S. L., & Dando, M. (2015). Sharks of the world: a fully illustrated guide. Wild Nature Press.
Huveneers, C. & Simpfendorfer, C. (2015). Heterodontus portusjacksoni. The IUCN Red List of Threatened Species. Retrieved from https://www.iucnredlist.org/species/39334/68625721
Klimley, A. P. (2013). The biology of sharks and rays. University of Chicago Press.
O’Gower, A. K., & Nash, A. R. (1978). Dispersion of the Port Jackson shark in Australian waters. Sensory Biology of Sharks, Skates, and Rays’.(Eds ES Hodgson and RF Mathewson.) pp, 529-544.
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Powter, D. M., & Gladstone, W. (2008). Embryonic mortality and predation on egg capsules of the Port Jackson shark Heterodontus portusjacksoni (Meyer). Journal of Fish Biology, 72(3), 573-584.
Rodda, K. R., & Seymour, R. S. (2008). Functional morphology of embryonic development in the Port Jackson shark Heterodontus portusjacksoni (Meyer). Journal of Fish Biology, 72(4), 961-984.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.
Vila Pouca, C., Gervais, C., Reed, J., & Brown, C. (2018). Incubation under Climate Warming Affects Behavioral Lateralisation in Port Jackson Sharks. Symmetry, 10(6), 184.