Featured Species: Epaulette Shark (Hemiscyllium ocellatum)

This week’s featured species is a small shark with some adaptations that sound more like science fiction than actual science. The Epaulette Shark (Hemiscyllium ocellatum) is a member of family Hemiscylliidae, small, elongated carpet sharks commonly referred to as the bamboo sharks (Bennett, Kyne, & Heupel, 2015). The epaulette shark is a small, reef dwelling shark with an elongated body. It has two relatively large dorsal fins and thick, muscular pectoral fins. As juveniles, the epaulette sharks have contrasting bands of color which break into spots as adults. They get their name from a prominent black spot surrounded by a characteristic white ring just above their pectoral fins, resembling military epaulettes worn on the shoulders of officers (Tricas et al, 1997).

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Tov, I.B. (Photographer). (n.d.). Epaulette Shark [Digital Image]. Retrieved from http://www.divephotoguide.com/

You may remember, the carpet sharks belong to the order Orectolobiformes. This order includes over 30 species in 7 families, including the wobbegongs, nurse sharks, zebra sharks, and even the whale shark (Parker, 2008). This means the little epaulette shark,  reaching a maximum of 3.5 feet (1 m) is a cousin of the largest fish in the ocean!

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Martin, R.A. (Author). (n.d.). Phylogenetic Tree of Order Orectolobiformes [Digital Image]. Retrieved from http://www.elasmo-research.org/

I mentioned that the epaulette shark had adaptations that sounded more like science fiction than fact. That’s because the epaulette shark has evolved the ability to walk on its robust pectoral fins (Mojetta, 1997)! And if that wasn’t incredible enough, it can survive for up to three hours without oxygen (Johnson, Kraver, Renshaw,  & Rummer, 2016). The epaulette shark inhabits shallow tide pools along coral reefs in northern Australia and New Guinea (Allen, Erdmann, & Dudgeon, 2013). When the tide moves out, this can leave the epaulette shark stranded in very shallow waters, sometimes only 6 inches (15 cm) deep (Bennett, Kyne, & Heupel, 2015). Waters this shallow can very quickly become severely hypoxic – or deprived of oxygen – and the waters can become very warm, reaching more than 86°F (30°C) (Bennett, Kyne, & Heupel, 2015). These waters would typically be a death trap for many species if they had to endure them for any length of time. But the epaulette shark is perfectly at home here. The epaulette shark can drop it’s blood pressure and wide its blood vessels, increasing the blood flow to important organs like the brain and the heart (Johnson et al., 2016). This allows the epaulette shark to survive in low oxygen for several hours until the tide comes back in and re-oxygenates the water. This shark also has the ability to travel from tide pool to tide pool by walking on its thick, robust pectoral fins; thereby giving it the ability to hunt in these shallow pools while the tide is out (Bennett, Kyne, & Heupel, 2015). It’s an amazingly hardy species!

 

BBC (Videographer). (2016 January 6). The Walking Shark- Great Barrier Reef with David Attenborough : Episode 3 Preview – BBC One [Video Clip]. Retrieved from https://www.youtube.com/

 

The epaulette shark does not face any threats from fisheries. It is well protected in Australia within the Great Barrier Reef Marine Park. While they local population in New Guinea may be under threat from over fishing and habitat destruction, the species is not currently threatened with extinction (Bennett, Kyne, & Heupel, 2015). However, there is one threat that affects every species in the ocean: ocean acidification. The oceans are currently absorbing high amounts of carbon dioxide due to climate change. This is causing a drop in the pH of the oceans to become more acidic. How will sharks be impacted in the future as the oceans become more acidic? A team of scientists recently used epaulette embryos to attempt to answer that very question. The egg cases were exposed to two treatments. The control was placed in current ocean conditions, with a pH of 8.14, with the other treatment being exposed to more acidic conditions with a pH of 7.88. The team then observed the embryo’s growth, development, and continued to observe the hatchlings for 30 days to measure survival rates (Johnson et al., 2016). The team found that their growth and development were virtually identical in both treatments; however, the hatching rate was 43% higher in the current pH than the elevated acidity and the survival rate was also increased in the current pH by 23% over the experimental treatment (Johnson et al., 2016). It is important to note that ocean acidification does not happen alone; it is often accompanied by increased temperatures and other environmental changes which this study did not measure.

Figure-1-Pub
Figure 1: Progression of growth using candling techniques in embryos reared in control (8.14 pH) and elevated CO2 (7.88 pH) conditions from 10 to 48 days post-fertilization. Yellow arrows point to the embryo’s head, and the scale bar in each image is 1 cm (Johnson, Kraver, Renshaw, & Rummer, 2016).

Shark Stats

Authority: Bonnaterre, 1788

Family: Hemiscylliidae; 17 species

Length: 3.5 feet (1 m)

Weight: 1.9 lbs (0.9 kg)

Habitat: Shallow, inshore waters and coral reefs of northern Australia and New Guinea

Depth: Surface to 131 feet (40 m)

Reproduction: Oviparous

Gestation: 120 days from egg laying to hatching

Litter Range: 20 egg cases per female per annum

Home Range: Northern Australia and New Guinea

Diet: Small benthic fishes and invertebrates

IUCN Status: Least Concern

(Trica et al, 1997; Heupel ,Whittier, & Bennett, 1999; Last & Stevens, 2009; Bennett, Kyne, & Heupel, 2015)

Thanks so much for checking out this week’s incredible walking epaulette shark! If you missed last week’s featured species, don’t miss the aw inspiring Scalloped Hammerhead. 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.

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.  Remember that climate change has real implications for all species! It only takes a moment to make a change that will last a lifetime. Until next time finatics!

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Featured Image Source

BBC (Videographer). (2016 January 6). The Walking Shark- Great Barrier Reef with David Attenborough : Episode 3 Preview – BBC One [Screen Capture]. Retrieved from https://www.youtube.com/

Literature Cited

Allen, G. R., Erdmann, M. V., & Dudgeon, C. L. (2013). Hemiscyllium halmahera, a new species of Bamboo Shark (Hemiscylliidae) from Indonesia. Aqua, International Journal of Ichthyology19, 123-136.

Bennett, M.B., Kyne, P.M. & Heupel, M.R. (2015). Hemiscyllium ocellatumThe IUCN red list of threatened species. Retrieved from https://www.iucnredlist.org/species/41818/68625284

Heupel, M. R., Whittier, J. M., & Bennett, M. B. (1999). Plasma steroid hormone profiles and reproductive biology of the epaulette shark, Hemiscyllium ocellatum. Journal of Experimental Zoology284(5), 586-594.

Johnson, M. S., Kraver, D. W., Renshaw, G., & Rummer, J. L. (2016). Will ocean acidification affect the early ontogeny of a tropical oviparous elasmobranch (Hemiscyllium ocellatum)?. Conservation physiology4(1).

Klimley, A. P. (2013). The biology of sharks and rays. University of Chicago Press.

Last, P.R. and Stevens, J.D. (2009). Sharks and Rays of Australia. Collingwood: CSIRO Publishing.

Mojetta, A. (1997). Sharks: History and biology of the lords of the sea. (E. McNulty, Ed.). San Diego: Thunder Bay Press.

Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.

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.

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