Featured Species: Giant Devil Ray (Mobula mobular)

This week’s featured species glides through the water like an angel, but it is named for its devilish appearance. The Giant Devil Ray (Mobula mobular) belongs to the family Mobulidae which includes other manta and devil rays like the Giant Manta Ray (Mobula birostris) (Tricas et al.,1997). Unlike the manta rays, the devil rays have sharp spines along its tail. These spines are venomous and are used in defense and social interactions within the species (Tricas et al., 1997). What gives the giant devil ray its name comes from its enormous size and its striking cephalic fins (Canese et al., 2011).  The giant devil ray is one of the largest species of rays; they have a disc width of 17 feet (5.2 m) and can weigh an incredible 3300 lbs (1500 kg) (McEachran, & Séret, 1990; Abudaya, Ulman, Salah, Fernando,  Wor, & di Sciara, 2018). Their devil-like appearance comes from their dark dorsal coloring with dark black splotch along the back of its head contrasted with a white under belly, as well as its horn-like cephalic fins. These fins are used to herd plankton into their mouths.

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Faulwetter, S. (2008). Mobula mobular [Digital Image]. Retrieved from https://www.flickr.com/

The giant devil ray has a limited home range. It is found exclusively in the Mediterranean and Adriatic Seas (Notarbartolo di Sciara, Serena, & Mancusi, 2015). They are notably absent from the Black Sea. There have been some reports of the giant devil ray in the Northeastern Atlantic, along the northwest coast of Africa, in Portugal, and even as far north as Southern Ireland (Notarbartolo di Sciara, 1987; Serena, 2005). However, these sightings may be attributed to another large circumtropical Mobulidae ray, the Spinetail Devil Ray (Mobula japanica). These two species are virtually identical in appearances; study into DNA comparison between the two devil rays may help to more clearly define each species home ranges (Notarbartolo di Sciara, Serena, & Mancusi, 2015).

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Left: Faulwetter, S. (Photographer). (2008). Mobula mobular [Digital Image]. Retrieved from https://www.flickr.com/ Right: Stevens, G. (Photographer). (n.d.). Mobula japanica [Digital Image]. Retrieved from https://iucnredlist.org/

The giant devil feeds on some of the smallest prey items in the sea: plankton. Like other oceanic giants like the giant manta ray (Mobula birostris)basking shark (Cetorhinus maximus) and the whale shark (Rhincodon typus), the giant devil ray is a filter feeder. Like the basking shark, the giant devil ray exhibit ram-jet feeding behaviors, which means that they rely on their forward movement to force water into their mouths and over their gills in order to feed. Within their gills, they have highly developed gill rakers, which are actually modified placoid scales (or skin denticles). The rakers densely packed along the gill arches and are used to trap calanoid copepods. The planktonic animals then travel from the rakers directly to the esophagus (Parker, 2008). Unfortunately, filter feeders are facing new challenges in this human driven age: microplastics. In an ongoing in Indonesia, reef manta rays (Manta alfredi) in Komodo National Park have been observed ingesting an estimated 40 to 90 pieces of microplastic per hour (Germanov, Marshall, Hedrawan, & Loneragan, 2015). The potential impacts from the ingestion of microplastics by large filter feeder elasmobranch species is still unclear; further research analyzing stomach contents and tissues using mass spectrometry to assess plastic associated toxins is still needed.

Gill Rakers
Stevens, G. (Photographer). (n.d.). Gill rakers filter particles from water, allowing manta and devil rays to feed [Digital Image]. Retrieved from http://blogspot.com/

Unlike other species of rays which are cold blooded and rely on the surrounding water temperature to thermoregulate their bodies, the rays in the family Mobulidae are warm-blooded – sort of. These endothermic rays have a modified circulatory system that allows them to elevate the temperatures of certain organs (such as the eyes, brain, heart, stomach, and trunk muscles) through a process called counter-current heat exchange.  Cool, oxygen depleted blood travels through the thin-walled veins from the red muscles, where it is warmed again by the oxygen rich blood from the gills through thick-walled arteries (Klimley, 2013). This internal network of veins and arteries is known as the rete mirable, or “wonderful net” in Latin (Klimley, 2013). This allows them to keep a body temperature that is warmer than the surrounding water temperature. Which is great for a species like the giant devil ray who live in chilly waters! Some sharks like the shortfin and longfin makos in family Lamnidae and the thresher sharks in family Alopiidae also have this ability.

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Counter-current heat exchange (n.d.). [Digital Image]. Retrieved from http://bio1152.nicerweb.com/

 

 

The giant devil ray is presently categorized as an Endangered species by the International Union for the Conservation of Nature (IUCN). They are highly vulnerable to fishery pressure within the Mediterranean, especially the purse seines used in Palestinian fisheries where they are taken at a likely unsustainable rate (Couturier, Bennett, & Richardson, 2013). They are also taken as bycatch in several fisheries including driftnets, purse seines, trammel nets, longlines, bottom trawls, pelgaic paired trawls, tuns traps, and hand harpoons (Scacco, Consalvo, & Mostarda, 2009; Akyol, Erdem, Ünal, & Ceyhan, 2006; Holcer, Lazar, Mackelworth, & Fortuna, 2013). When they are taken as bycatch, they are typically discarded. Occasionally they are landed and marketed for their meat (Notarbartolo di Sciara, Serena, & Mancusi, 2015). The giant devil ray is also taken in illegal drift net fisheries. The European Union banned drift net fishnet fisheries by several regulations, including the European General Fisheries Commission for the Mediterranean Sea, the International Commission of Atlantic Tuna; however, illegal fisheries still exist.  The Mediterranean is also one of the busiest oil shipping lanes in the world, which brings in heavy maritime traffic and exposes it to accidental spills. As an epipelagic species, the giant devil ray are vulnerable to these types of human interactions.

Dorsal-view-of-the-male-specimen-of-the-giant-devil-ray-Mobula-mobular-by-caught-by-a_W640
Fig. 2. Dorsal view of the male specimen of the giant devil ray Mobula mobular by-caught by a pelagic pair trawler in the central Adriatic Sea (Scacco, Consalvo, & Mostarda, 2009).

 

In an effort to conserve the giant devil ray, in 2001 they were included in Annex II of the List of endangered or threatened species to the Protocol Concerning Special Protected Areas and Biological Diversity in the Mediterranean of the Barcelona Convention. Annex II strictly protected fauna species to the Bern Convention. In 2012, parties within the Barcelona Convention further agreed that species could not be retained on board, transported, landed, transferred, stored, sold, displayed, or offered for sale. In addition, they had to be released alive and unharmed to the best extent possible. Efforts to work with fishermen on the proper release methods to ensure a successful release will hopefully improve catch mortality rates. Continued monitoring of the species and sustainable management practices are vital for the survival for the species.

FuturismoAzores (Videographer). (2018). Mobula mobular [Video Clip]. Retrieved from https://www.youtube.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.Mobula-mobular_Csotonyi_01_201907020330

Ray Stats

Authority: Bonnaterre, 1788

Family: Mobulidae, 10 species

Disc Width: Up to 17 feet (5.2 m)

Weight: Up to 3300 lbs (1500 kg)

Habitat: Continental and insular shelves, close inshore to well offshore

Depth: Surface to several thousand meters

Reproduction: Ovoviviparity

Gestation: Unknown

Litter Range: 1 pup

Home Range: Limited to the Mediterranean and Adriatic Seas, possibly the adjacent North Atlantic Ocean

Diet: Schooling bony fishes, stingrays, small sharks, skates, large crustaceans

IUCN Status: Endangered

(Wourms, 1977; Tricas et al., 1997; Abudaya, Ulman, Salah, Fernando,  Wor, & di Sciara, 2018); Notarbartolo di Sciara, Serena, & Mancusi, 2015)

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. Proceeds benefit shark research and conservation with a donation to Project AWARE!

Thanks so much for checking out the beautiful Giant Devil Ray! If you missed last week’s featured species, please be sure to check out the wild Smooth HammerheadSmooth Hammerhead! If there is a species of elasmobranch 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. Also connect with me on Instagram and Facebook for even more elasmo fun!

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!

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Featured Image Source

Faulwetter, S. (Photographer). (2008). Mobula mobular [Digital Image]. Retrieved from https://www.flickr.com/photos/sarahfaulwetter/2992718180/

Literature Cited

Abudaya, M., Ulman, A., Salah, J., Fernando, D., Wor, C., & di Sciara, G. N. (2018). Speak of the devil ray (Mobula mobular) fishery in Gaza. Reviews in fish biology and fisheries28(1), 229-239.

Akyol, O., Erdem, M., Ünal, V., & Ceyhan, T. (2006). Investigations on drift-net fishery for swordfish (Xiphias gladius L.) in the Aegean Sea. Turkish Journal of Veterinary and Animal Sciences29(6), 1225-1231.

Canese, S., Cardinali, A., Romeo, T., Giusti, M., Salvati, E., Angiolillo, M., & Greco, S. (2011). Diving behavior of the giant devil ray in the Mediterranean Sea. Endangered species research14(2), 171-176.

Couturier, L. I., Bennett, M. B., & Richardson, A. J. (2013). Mystery of giant rays off the Gaza strip solved. Oryx47(4), 480-480.

Germanov, E., Marshall, A., Hedrawan, I. G., & Loneragan, N. (2015). Plastics on the Menu : Microplastics Present in Indonesian Manta Ray Feeding Habitats.

Holcer, D., Lazar, B., Mackelworth, P., & Fortuna, C. M. (2013). Rare or just unknown? The occurrence of the giant devil ray (Mobula mobular) in the Adriatic S ea. Journal of applied ichthyology29(1), 139-144.

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

McEachran, J. D., & Séret, B. (1990). Rhinopteridae. In ‘Check-list of the Fishes of the Eastern Tropical Atlantic (CLOFETA)’.(Eds JC Quero, JC Hureau, C. Karrer, A. Post, and L. Saldanha.) Vol. 1.

Notarbartolodi Sciara, G. (1987). A revisionary study of the genus Mobula Rafinesque, 1810 (Chondrichthyes: Mobulidae) with the description of a new species. Zoological Journal of the Linnean Society91(1), 1-91.

Notarbartolo di Sciara, G., Serena, F. & Mancusi, C. (2015). Mobula mobularThe IUCN Red List of Threatened Species. Retrieved from  https://www.iucnredlist.org/

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

Scacco, U., Consalvo, I., & Mostarda, E. (2009). First documented catch of the giant devil ray Mobula mobular (Chondrichthyes: Mobulidae) in the Adriatic Sea. Marine Biodiversity Records2.

Serena, F. (2005). Field identification guide to the sharks and rays of the Mediterranean and Black Sea. Food & Agriculture Org..

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.

Wourms, J. P. (1977). Reproduction and development in chondrichthyan fishes. American Zoologist17(2), 379-410.

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