Featured Species: Genie’s Dogfish (Squalus clarkae)

This week’s featured species was described earlier this year as a new deep water species. A paper published in Zootaxa in July of this year revealed that after DNA testing and morphological comparisons the Genie’s Dogfish was a unique species, and not a Shortspine spurdog (Squalus mitsukurii), as previously thought (Pfleger, Grubbs, Cotton, Daly-Engel, 2018). Genie’s dogfish is characterized by an elongated fusiform body with a small interorbital space (or the space between their eyes), and a short caudal tail (Pfleger et al., 2018).

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Figure 4A. Adult female Squalus clarkae sp. nov. holotype (catalog #UF239318) from the Gulf of Mexico (lateral view photo) 4B: Adult female S. clarkae sp. nov. from the Gulf of Mexico (lateral view sketch) (Pfleger et al,. 2018)

 

The Genie’s dogfish shark jaw has a set of teeth that are relatively the same in the upper and lower jaws. The teeth have a strong, laterally positioned cusp. The teeth are smooth, lacking serrations or additional cusplets (Pfleger et al,. 2018). Like other deep water dwelling dogfish sharks, the Genie’s dogfish likely feeds on small benthic bony fishes, invertebrates, and crustaceans.

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Left: Figure 2. Lower jaw from adult male (TL = 63 cm) Squalus clarkae sp. nov. (uncatalogued specimen) Right: Figure 3. Upper jaw from adult male (TL = 63 cm) Squalus clarkae sp. nov. (uncatalogued specimen) (Pfleger et al,. 2018)

 

Every elasmobranch species has dermal denticles, teeth-like scales along their bodies. These denticles reduce drag and turbulence, allowing the shark to swim faster and more easily in the water (Skomal, 2016). The denticles of the Genie’s dogfish shark is relatively triangular with three ridges running along the length of the denticle  (Pfleger et al,. 2018). One characteristic of dogfishes is rough skin. After seeing their dermal denticles up close, do you have a clearer picture of why a shark’s skin can feel so rough? Especially when you rub from tail to snout?

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Figure 1A. Denticles from adult male (TL = 61 cm) Squalus clarkae sp. nov. (Pfleger et al,. 2018)

 

Like many species of shark, Genie’s dogfish give birth to live young. The young are incubated inside the mother’s womb attached to a yolk sac. When the sac is depleted, and the pups are fully developed, mom will give birth to a litter of 1 to 15 pups. This process can take up to 2 years! With such a slow reproductive rate, and a slow growth rate, these sharks could potentially be in harm’s way as commercial fisheries move into deeper and deeper waters.

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Figure 5A. Dorsal and ventral views of Squalus clarkae sp. nov. embryo with yolk sac from the Gulf of Mexico (photo, uncatalogued specimen) (Pfleger et al,. 2018)

 

In recent years, commercial fisheries have turned their attention towards deep sea waters. As a result deep water research and conservation efforts have become more of a focus. Since 2000, 2/3 of the new Chondrichthyan species discovered have been from waters below 656 feet (200 meters) (Cotton and Grubbs, 2015).  But deep water research, and in turn it’s conservation, isn’t easy. It’s difficult to access, and difficult to access population sizes and trends. However, we do know that deep water elasmobranch species exhibit some of the lowest genetic diversities among the Chondrichthyans. Combined with slow growth rates and low fecundity, this makes their rebound potentials from deep water fishing pressures very low (Rigby and Simpfendorfer, 2015). Which is why there is a growing focus on conserving these deep water species.

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Sia, K. (Photographer). (2007). Fish seized in 2007 at the port of Abidjan, Cote d’Ivoire, from two Chinese ships that were intercepted bottom trawling, disregarding national fishing laws [Digital Image]. Retrieved from https://www.newsdeeply.com/

If you’re wondering who Genie is in the Genie’s dogfish’s name, clarkae should be your next clue.  This new species was named in honor of the Shark Lady, Dr. Eugenie Clark. Dr. Clark was a pioneer, not just for women in STEM, but in marine biology and shark science. She discovered a number of new species, has several species named for her, and dedicated her life to dispelling the fears of sharks (Stone, 2015). She has inspired so many marine scientists and conservationists, including myself, to enter the field and get involved in shark research and conservation. Dr. Clark passed away in February of 2015 from non-smoking related lung cancer at the age of 92.

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Doubilet, D. (Photographer). (n.d.). Clark examines a whale shark pup in her lab [Digital Image]. Retrieved from https://news.nationalgeographic.com/

I’m delighted to announce a partnership with the wonderfully talented Julius Csotonyi! Julius creates stunning shark coloring sheets that are fun and educational for all ages. From time to time you’ll see Julius’ work featured right here and on my other social media platforms! You can find more coloring sheets in the store! You are welcomed to download these beautiful sheets and enjoy them with family and friends.

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Shark Stats

Authority: Pfleger, Grubbs, Cotton, & Daly-Engel, 2018

Family: Squalidae, 35 species

Length: Maximum 2.3 feet (0.7 m)

Weight: Maximum weight undetermined

Habitat: Upper continental and insular slopes; temperate to tropical waters

Depth: Below 656 feet (200 m)

Reproduction: ovoviviparous

Gestation: Up to 2 years

Litter Range: 1 – 15 pups

Home Range: Western Atlantic and Gulf of Mexico

Diet: Benthic fishes, invertebrates, and crustaceans

IUCN Status: Data Deficient

(Pfleger et al., 2018)

Thanks so much for checking out the Genie’s Dogfish shark! It is always so exciting to see new species brought to light! Remember to hope over to last week’s featured species: the Daggernose 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.

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 finatics!

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Featured Image Source

Csotonyi, J. (Artist). (2018). Squalus clarkae [Digital Image]. Retrieved from https://www.dropbox.com/

Literature Cited

Cotton, C. F., & Grubbs, R. D. (2015). Biology of deep-water chondrichthyans: Introduction. Deep Sea Research Part II: Topical Studies in Oceanography115, 1-10.

Pfleger, M. O., Grubbs, R. D., Cotton, C. F., & Daly-Engel, T. S. (2018, July 9). Squalus clarkae sp. nov., a new dogfish shark from the Northwest Atlantic and Gulf of Mexico, with comments on the Squalus mitsukurii species complex. Zootaxa.

Rigby, C., & Simpfendorfer, C. A. (2015). Patterns in life history traits of deep-water chondrichthyans. Deep Sea Research Part II: Topical Studies in Oceanography115, 30-40.

Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.

Stone, A. (2015). “Shark Lady” Eugenie Clark, Famed Marine Biologist, Has Died. Retrieved November 8, 2018, from https://news.nationalgeographic.com/2015/02/150225-eugenie-clark-shark-lady-marine-biologist-obituary-science/

Next Post

Featured Species: Atlantic Stingray (Hypanus sabinus)

Previous Post

Featured Species: Daggernose Shark (Isogomphodon oxyrhynchus)

 

 

 

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