This week’s featured species is a primitive shark species that dwells in deep water. The sharpnose sevengill shark (Heptranchias perlo) is a slender, fusiform bodied cow shark that is typically found in tropical and temperate waters between 88 to 2360 feet (27 to 720 m) but has been observed at depths of 3280 feet (1,000 m) (Paul & Fowler, 2003; Ebert, Fowler, & Dando, 2015). Unlike most shark species, which have five pairs of gills, the sharpnose sevengill shark has seven pairs of gill slits, as their name suggests. All members of the family Hexanchidae are characterized by an additional pair, or pairs, of gill slits. They are considered one of the most primitive shark forms, resembling ancient shark species found in the fossil record nearly 270 million years ago (Mojetta, 1997).
Despite a patchy worldwide distribution in tropical and temperate waters, the shaprnose sevengill is a relatively uncommon species (Paul & Fowler, 2003). Coupled with their deep water dwelling nature, studying them is rather difficult. The little we know about their biology has mostly come from dissection from specimens caught as bycatch in commercial bottom trawl and longline fisheries. We do know that these are very capable hunters, feeding on small open sea bony fishes, small sharks and rays, squids, and shellfish. They are ovoviparious, giving birth to live young in litters ranging from 6 to 20 pups at a time (Tanaka & Mizue, 1977). However, the frequency of their reproduction cycle and the gestation time is unknown (Paul & Fowler, 2003).
Below is a video of a dissection of a specimen from the Australian Museum. Please skip it if you don’t like seeing this kind of thing, but this is a really neat video, I promise!
Australian Museum (Videographer). (2015). Sharpnose Sevengill Shark dissection [Video Clip]. Retrieved from https://www.youtube.com/
I decided to featured this deepwater shark this week, because just this week a research team released a video that captured a sharpnose sevengill shark for the first time ever! The team filmed the shark in May of 2018 while in the Bahamas at 2,600 feet (792 m) in a region west of Nassau known as the Tongue of the Ocean(Phillips, Shipley, Halvorsen, Sternlicht, & Gallagher, 2019). It was also the first time the sharpnose sevengill had ever been observed in that locality. The paper was published earlier this week and can be reviewed here. Be sure to check out the video below! I still cannot get over how graceful these sharks are. It’s just memorizing.
Beneath the Waves (Videographer). (2019 January 15). Discovery: sharpnose sevengill shark at 2600 feet deep! [Video Clip]. Retrieved from https://www.facebook.com/BeneathTheWavesInc
Authority: Bonnaterre, 1788
Family: Hexanchidae; 37 species
Length: Maximum of 4.5 feet (1.4 m)
Weight: Maximum weight unknown
Habitat: Outer continental shelves, slopes, and oceanic seamounts
Depth: Typically found between 88 to 2360 feet (27 to 720 m); maximum depth of 3280 feet (1,000 m)
Litter Range: 6 – 20 pups
Home Range: Patchy tropical and temperate waters; not found in the the Northeastern Pacific
Diet: Small open sea fishes, small sharks and rays, squids, and shellfish
IUCN Status: Near Threatened
(Paul & Fowler, 2003; Ebert, Fowler, & Dando, 2015)
Thanks so much for checking out the Sharpnose Sevengill Shark! If you missed last week’s featured species, please be sure to check out the Port Jackson Shark! 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
Beneath the Waves (Videographer). (2019 January 15). Discovery: sharpnose sevengill shark at 2600 feet deep! [Sceenshot]. Retrieved from https://www.facebook.com/BeneathTheWavesInc
Ebert, D. A., Fowler, S. L., & Dando, M. (2015). Sharks of the world: a fully illustrated guide. Wild Nature Press.
Mojetta, A. (1997). Sharks: History and biology of the lords of the sea. (E. McNulty, Ed.). San Diego: Thunder Bay Press.
Paul, L. & Fowler, S. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Heptranchias perlo. The IUCN Red List of Threatened Species. Retrieved from https://www.iucnredlist.org/species/41823/10572878
Phillips, B. T., Shipley, O. N., Halvorsen, J., Sternlicht, J. K., & Gallagher, A. J. (2019). First in situ observations of the sharpnose sevengill shark (Heptranchias perlo), from the Tongue of the Ocean, Bahamas. Journal of the Ocean Science Foundation, 32, 17–22.
Tanaka, S. & Mizue, K. (1977). SStudies on Sharks―XI Reproduction in Female Heptranchias perlo. Bulletin of the Faculty of Fisheries Nagasaki University No. 42, 1–9.