Featured Species: Atlantic Stingray (Hypanus sabinus)

This week’s featured species is a relatively small elasmobranch that has recently made some big waves. The Atlantic Stingray (Hypanus sabinus) is a small ray, only measuring about 1.5 feet (0.45 m) across, found in the Western Atlantic and Gulf of Mexico. This species is characterized by a yellow-brown dorsal side with an elongated snout, and white ventral belly. This ray is member of the family Dasyatidae, which contains about 70 species including the Southern Stingray (Dasyatis americana); and until 2016 when the family was revised, the Atlantic stingray was known as Dasyatis sabina (Last, Naylor, & Manjaji-Matsumoto, 2016).

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Murray, C. (Photographer). (n.d.). Atlantic Stingray [Digital Image]. Retrieved from https://www.inaturalist.org/

Like the bull shark (Carcharhinus leucas), the Atlantic stingray is euryhaline, or able to tolerate a variety of salinity (Klimley, 2013). They are frequently observed from coastal marine environments, through brackish estuaries, and into freshwater rivers and lake systems. In order to maintain balance within their bodies, the Atlantic sting ray produces lower concentrations of sodium, chloride, and urea than other species living in higher salinity environments (Klimley, 2013). And like the bull shark, they secret large amounts of urine while in freshwater environments to rid themselves of excess water gained through osmosis across their gills (Klimley, 2013). Just imagine drinking your body weight in water and having to constantly pee all day, while going about your daily routine. It’s just crazy and amazing what their bodies are capable of regulating!

 

 

Da Good Stoff (Videographer). (2018 October 12). Freshwater Stingray (Hypanus sabinus) [Video Clip]. Retrieved from https://www.youtube.com/

 

Most elasmobranchs exhibit sexual dimorphism. In most species the females are larger than the males, have tougher, thicker skin, and lack external claspers of the males. In skates and rays, it is common for males to also change their tooth morphology during mating season. The male Atlantic stingrays have sharper, pointer teeth in the center of their jaws than the females, who have flat, plate-like crushing teeth. During the spring and summer months, the central teeth of the males will develop multiple cusps (Bigelow & Schroeder, 1953). These sharp, multi-cusped teeth, help the male get a better grasp on the female, allowing him to bend his body around her more effectively during copulation (Klimley, 2013). In the fall and winter months, the males lose these cusped teeth and replace them with the blunt, molariform teeth similar to the females.

Dasyatis-sabina-05-06
Hypanus sabinus dentition A. tooth band of female, B. tooth band of male (Bigelow & Schroeder, 1953).

 

In April of 2010, Deepwater Horizon exploded in the Gulf of Mexico. Since the disaster, nearly five million barrels of crude oil have spilled into Gulf and over 1100 miles (1773 km) of coastline has been impacted (Cave & Kajiura, 2018).  Over 10 million gallons of crude oil can still be found in the sediment at the bottom of the Gulf of Mexico, which we are still struggling to understand the potential implications for wildlife and the ecosystem. A study published in Scientific Reports is the first to detect significantly impaired olfactory (sense of smell) function in the Atlantic stingray in as little as 48 hours after exposure to crude oil (Cave & Kajuira, 2018).  In the study, the test stingrays were held in a tank for 48 hours while being exposed to high-energy water accommodated fraction (HEWAF) oil solution in a concentration equal to measurements taken along the Louisiana coast line following Deepwater Horizon. Control stingrays were held in identical tanks, with identical conditions without the HEWAF solution exposure. Five amino acids that are known to be olfactory stimulants for the Atlantic stingray were presented to both the test rays and the control rays and the time it took for the rays to respond to the stimuli were recorded. The study revealed a significant increase in response time in the test group in response to the amino acids phenylalanine, glutamic acid, and cysteine (Cave & Kajuira, 2018). These findings clearly indicate impairment in the olfactory system in these rays after a short period of exposure to crude oil. This could have drastic impacts for many elasmobranch species: impacting fitness, leading to premature death, and even causing trophic cascades in ecosystems. It could also have potential implications for species that lay their eggs in sediment laced with crude oil residue. The developing embryos could be exposed to high concentrations of crude oil during crucial development periods. This study brings forth many more questions that require our attention.

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Figure 2. Mean (+standard error) Electro-olfactogram (EOG) response duration (seconds) in Hypanus sabinus from five highly stimulatory amino acids. A representative EOG response is shown to indicate the measured parameter. ALA, alanine; PHE, phenylalanine; GLU, glutamic acid; ARG, arginine; CYS, cysteine. * indicates significant differences between control and oil exposed animals for each amino acid (Mann-Whitney U, p < 0.05) (Cave & Kajiura, 2018).

 

Ray Stats

Authority: Lesueur, 1824

Family: Dasyatidae; about 70 species

Length: 1.5 feet (0.45 m) Disc width

Weight: 11 lbs (4.9 kg)

Habitat: Freshwater rivers and lakes, estuaries, brackish waters, coastal marine waters of temperate and tropical Atlantic Ocean and Gulf of Mexico

Depth: Surface to 82 feet (25 m)

Reproduction: Aplacental viviparous

Gestation: 4 months

Litter Range: 2 – 3 pups

Home Range: Western Atlantic and Gulf of Mexico

Diet: Benthic fishes, invertebrates, and crustaceans

IUCN Status: Least Concern

(Funicelli, 1975; Snelson Jr, Williams-Hooper, & Schmid, 1988;

Johnson, & Snelson Jr, 1996; Piercy, Snelson, & Grubbs ,2016)

Thanks so much for checking out this week’s flat shark: the Atlantic Stingray! If you missed last week’s recently discovered species, be sure to pop back and check out Genie’s Dogfish. 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

Kaiser, S. (Photograher). (2007 March 23). Atlantic stingray (Dasyatis sabina) at Siesta Key, Florida [Digital Image]. Retrieved from https://en.wikipedia.org/

Literature Cited

Bigelow, H. B., & Schroeder, W. C. (1953). Fishes of the Western North Atlantic. Part 2.(Sawfishes, Guitarfishes, Skates, Rays and Chimaeroides).

Cave, E. J., & Kajiura, S. M. (2018). Effect of Deepwater Horizon Crude Oil Water Accommodated Fraction on Olfactory Function in the Atlantic Stingray, Hypanus sabinus. Scientific Reports8(1), 15786.

Funicelli, N. A. (1975). Taxonomy, feeding, limiting factors, and sex ratios of Dasyatis americana, Dasyatis sayi, and Narcine brasiliensis.

Johnson, M. R., & Snelson Jr, F. F. (1996). Reproductive life history of the Atlantic stingray, Dasyatis sabina (Pisces, Dasyatidae), in the freshwater St. Johns River, Florida. Bulletin of Marine Science59(1), 74-88.

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

Last, P. R., Naylor, G. J., & Manjaji-Matsumoto, B. M. (2016). A revised classification of the family Dasyatidae (Chondrichthyes: Myliobatiformes) based on new morphological and molecular insights. Zootaxa4139(3), 345-368.

Piercy, A., Snelson, F.F. & Grubbs, R.D. (2016). Hypanus sabinusThe IUCN Red List of Threatened Species 2016. Retrieved from http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T60158A104136233.en

Snelson Jr, F. F., Williams-Hooper, S. E., & Schmid, T. H. (1988). Reproduction and ecology of the Atlantic stingray, Dasyatis sabina, in Florida coastal lagoons. Copeia, 729-739.

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