Photo of a spotted eagle ray feeding along the ocean floor. Courtesy of Sheraca.Prey
        Spotted eagle rays are an important component of the marine food web. Aetobatus narinari are carnivorous benthic feeders and have six primary prey categories: gastropods, bivalves, crustaceans, echinoderms, polychaete, and other mollusks (Schluessel et al. 2010). Approximately half of an eagle ray’s diet is composed of gastropods, such as the endangered queen conch (Strombus gigas), while the other half is mainly made up of bivalves, including giant clams and calico clams (Macrocallista maculata) (Randall 1967, Ajemian et at. 2012). Occasionally, eagle rays will also feed on small fish, squid, and cephalopods (Silliman and Gruber 1999).

Hammerhead sharks are known predators of spotted eagle rays and sometimes use a pin and pivot maneuver to consume them. Photo courtesy of Wikimedia Commons.        In the marine food web, A. narinari feed on organisms on the benthic floor and in turn get preyed upon by larger organisms. Due to their massive sizes, only the largest predators pose a threat to this species. Sharks are their main predators. Specific sharks that target A. narinari include the great hammerhead (Sphyrna mokkarran), tiger (Galecerdo cuvier), bull (Carcharhinus leucas) and Carribbean reef sharks (Carcharhinus perezi) (Silliman and Gruber 1999). Hammerhead sharks have been observed to use a pin and pivot technique to capture and consume eagle rays (Chapman and Gruber 2002). The shark pins the ray to the ocean floor with its cephalofoil (flat portion of head seen in the photo to the left) and then pivots its body until the ray’s head is in its jaws. 

Parasitic Interactions
        A. narinari are susceptible to a variety of parasites including trematodes, leeches, and tapeworms. At least four species of Acanthobothrium are known to have parasitic interactions with A. narinari. In 1995, a previously undescribed species of Acanthobothrium was discovered in the spiral valve of a spotted eagle ray in the Gulf of Nicoya. The parasite was named Acanthobothrium nicoyaense and is a Cestode in the Phylum Platyhelminthes (Brooks and McCorquodale 1995).           Photo of a cleaner wrasse and a spotted eagle ray. Cleaner wrasse can help control parasite infestations. Courtesy of Sheraca.
         Another parasite that can infect spotted eagle rays is a trematode called Clemacotyle australis. In a study conducted by a zoo in the Netherlands, infestations of C. australis have been shown to induce stressful behavioral changes in spotted eagle rays (Janse and Borgsteede 2003). A. narinari in captivity have been observed leaping out of the water, swimming against strong currents, and rubbing their bodies along the bottom of the aquarium in response to the skin trematodes. These actions caused hemorrhages to develop on their fins and altered their dorsal coloration due to mucus buildup. If left untreated, the infection, along with the immense energy expelled by the organism to purge itself, can result in death. The addition of cleaner wrasse (Labriodes dimidiatus) to A. narinari display tanks were shown to maintain the infestation of C. australis at a level where they did not negatively impact the health of the rays.

Aetobatus narinari & Homo sapiens
        Some small fisheries, mainly in the Southern Gulf of Mexico and Venezuela, specifically target spotted eagle rays for their meat (Tagliafico et al. 2012). Meat obtained from A. narinari is readily marketable in Venezuela and is the main component of a popular dish. In other areas, the rays are often unintentionally caught as bycatch from industrial fisheries, since they dwell near the shore where fishing pressures are the greatest, as mentioned in the habitat section. A. narinari are classified by the International Union for Conservation of Nature (IUCN) Red List as near threatened. Factors that have contributed to their status include increased fishing pressures for numerous marine species, overexploitation of these organisms and their primary food sources (including bivalves and gastropods), and increased competition for food and space due to a rise in the cownose ray (R. bonasus) population (Cuevas-Zimbron et al. 2010).
            Elasmobrachs, including Aetobatus narinari, have stingers located on the dorsal side of their tails. Since stingrays are generally peaceful creatures, they use their stingers primarily as a form of defense when provoked (Junior 2013). Their stingers are covered with a layer of specialized epidermal cells that produce and secrete venom (Pedroso 2007).  Humans often accidentally come into contact with these organisms while walking through waters near their habitat or while attempting to release them from hooks and nets. Humans inoculated with their venom can experience serious side effects, including acute inflammation and pain, skin necrosis, and in some extreme cases, death (Pedroso 2007).
            Spotted eagle rays have also proven to be useful in research. Researchers can use tissues found in their stinger to extract and analyze their DNA (Janse et al. 2013). As the number of fishes worldwide starts to deteriorate, breeding programs for animals in captivity become important. DNA research and analysis can help maintain genetic variability in captivity, and ensure successful future generations. Lost stingers have the ability to easily grow back, so this method of DNA acquisition is non-invasive and causes no lasting damage to the organism. This DNA extraction method is also applicable to other species of elasmobranchs. If you're interested in learning more about the research being conducted on spotted eagle rays, check out this video.     

                             Researchers capturing and tagging spotted eagle ray. Photo courtesy of Mote Marine Laboratory

Continue on to learn about some really cool Facts, or return to the Home page.