“Myliobatis australis”
The Australian Bull Stingray is found in the southern waters of Australia from Jurien Bay, Western Australia around the southern coast, to Tasmania and up the east coast as far as Moreton Bay in southern Queensland. The Australian Bull Stingray lives in the depth range of 5 to 85 meters environment. The genus name Myliobatis, is derived from the Greek ‘mylo’ meaning mill and ‘batis-dos’ translated as a ray. There are no known synonyms referring to this species in past scientific literature. World-famous Steve “the Crocodile Hunter” Irwin known for seeking out and handling some of the most dangerous animals in existence, died on September 4, 2006 in a shocking accident with a Australian Bull Stingray. Stingrays are considered by most experts to be docile creatures, only attacking in self-defense. Most stingray-related injuries to humans occur to the ankles and lower legs, when someone accidentally steps on a Australian Bull Stingray buried in the sand and the frightened ray flips up its dangerous tail. Officials are calling the Florida incident a totally freak occurrence. In the early stages of examining the Steve Irwin accident, some experts have hypothesized that the combined positions of Irwin (above the fish) and his cameraman (in front of the fish) could have made the stingray feel trapped and triggered a defensive attack; others point out that completely unprovoked stingray attacks are not unheard of. It is found between the surf zone and depths of 65 meters (213 feet) or more and also enters estuaries & lagoons. It frequents both the bottom, surface and sometimes leaps from the water. The Australian Bull Stingray feeds on various invertebrates including crabs, squid, prawns, gastropods and mollusks. It is viviparous and gives birth to live young. The gestation period is believed to be about 1 year and 3 to 4 young may be carried at one time.
Stingray-related fatalities in humans are extremely rare, partly because a stingray’s venom while extraordinarily painful, isn’t usually deadly unless the initial strike is to the chest or abdominal area. In Irwin’s case, the barb actually pierced his heart. James Bertakis was also stabbed in the chest and possibly in the heart, but he did not attempt to remove it which could prove to be part of the reason he survived the attack. News agencies have reported that Irwin’s encounter was with an Australian Bull Stingray, estimated to weigh about 220 pounds (100 kilograms). Irwin was snorkeling in about 6 feet (2 meters) of water, filming a new documentary entitled “Ocean’s Deadliest” off the eastern coast of Australia. Irwin was swimming with one of the larger species of rays out there. Australian Bull Stingrays can be up to 4 feet (1.2 meters) wide and 8 feet (2.4 meters) long but all stingrays use the same attack mechanism regardless of size. The mechanism is called “asting”, up to 8 inches (20 centimeters) long in a Australian Bull Stingray located near the base of the tail. The sting contains a sharp spine with serrated edges or barbs, that face the body of the fish. There is a venom gland at the base of the spine and a membrane-like sheath that covers the entire sting mechanism. When a stingray attacks, it needs to be facing its victim because all it does is flip its long tail upward over its body so it strikes whatever is in front of it. If the stingray loses one of its barbs while defending itself, it immediately begins to grow a new one. Australian Bull Stingrays shed and re-grow their spines on a regular basis regardless of whether they use them. The stingray doesn’t have direct control over the sting mechanism, only over the tail. In most cases when the sting enters a person’s body, the pressure causes the protective sheath to tear. When the sheath tears, the sharp-serrated edges of the spine sink in and venom flows into the wound.
The barb is covered with rows of sharp flat spines, composed of vasodentin. Vasodentin is an incredibly strong cartilaginous material which can easily cut through flesh. The undersides of the spines contain 2 longitudinal grooves which run along the length of the spine and enclose venom-secreting cells. Both the venom-secreting tissues & vasodentin are enveloped in an epidermis that tears open when the barb is plunged into a victim. Some spines may break off as the barb exits the wound and stay within the victim causing prolonged envenoming. The venom is composed of enzymes, 5-nucleotidase with phosphodiesterase and the neurotransmitter serotonin. Serotonin causes smooth muscle to severely contract and it is this component that makes the venom so painful. The enzymes cause tissue & cell death. If the venom is introduced into an area like the ankle, it can usually be treated. Heat breaks down stingray venom and limits the amount of damage it can do. If not treated quickly enough, amputation might be necessary. If the venom enters the abdomen or chest cavity, the resulting tissue death can be fatal because of the major organs located in the vicinity. If the spike enters the heart as is reported to be the case in Steve Irwin’s accident, the results are typically fatal. While an Australian Bull Stingray‘s venom can do serious damage, the most destructive part of the sting mechanism can actually be the barbs on the spine. The sharp tip of the sting enters a person pretty smoothly, but its exit is roughly equivalent to backing up over those “severe tire damage” blades. Remember that the points of the barbs are facing the stingray. Even if venom weren’t involved at all, pulling the spike out of a human’s chest or abdomen could be enough to cause death from the massive tearing of tissue that results.