vacationers venture into the surf that may be laden with congregating (for spawning purposes) rays.
Freshwater species do not inhabit U.S. waters. They are found in South America, Africa, and Southeast Asia.
Rays are small (several inches) to large (up to 12 by 6 feet) creatures observed lying on top of the sand
and mud or partially submerged, with only the eyes, spiracles, and part of the tail exposed. Their flattened
bodies are round-, diamond-, or kite-shaped, with wide pectoral fins that look like wings. Rays are
nonaggressive scavengers and bottom feeders that burrow into the sand or mud to feed on worms, mollusks,
and crustaceans. The mouth and gill plates are located on the ventral surface of the animal.
The venom organ of stingrays consists of one to four venomous stings on the dorsum of an elongate,
whiplike caudal appendage. The stinging ability of rays may be divided into four categories: the gymnurid
type (butterfly rays or Gymnuridae), with a poorly developed sting of up to 2.5 cm placed at the base of a
short tail; the myliobatid type (eagle and bat rays or Myliobatidae), with a sting of up to 12 cm placed at the
base of a cylindrical caudal appendage that terminates in a long whiplike tail; the dasyatid type (stingrays and
whiprays or Dasyatidae), with a sting of up to 37 cm placed at the base or further out on the caudal appendage
that terminates in a long whiplike tail; and the urolophid type (round stingrays or Urolophidae), with a sting of
up to 4 cm located at the base of a short, muscular, well-developed caudal appendage. The efficiency of the
apparatus is related to the length and musculature of the tail and to the location and length of the sting. Eagle
rays and some mantas (Atlantic Mobular mobular and Pacific Mobula japanica) have a stinging apparatus,
but it is less of a threat because the spine is located at the base of the tail and is not well adapted as a striking
organ. However, manta skin is rough and can abrade unprotected human skin. A stingray "hickey" is a mouth-
bite created by powerful grinding plates that produces superficial erosions and ecchymosis in an oral pattern.
Persons who hand feed stingrays may incur this type of injury. The suction force generated by a stingray is
sufficient to pull in a large amount of soft tissue, say, from a thigh. This may result in a large and painful
contusion and/or hematoma.
In all cases, the venom apparatus of stingrays consists of a bilaterally retroserrate spine or spines and
the enveloping integumentary sheath or sheaths. The elongate and tapered vasodentine spine is firmly attached
to the dorsum of the tail (whip) by dense collagenous tissue and is edged on either side by a series of sharp
retrorse teeth. Along either edge on the underside of the spine are the two ventrolateral glandular grooves,
which house the soft venom glands. The entire spine is encased by the integumentary sheath, which also
contains some glandular cells. The sting is often covered with a film of venom and mucus. The spine is
replaced if detached.
Stingray "attacks" are purely defensive gestures that occur when an unwary human handles, corners,
or steps on a camouflaged creature while wading in shallow waters. The tail of the ray reflexively whips
upward and accurately thrusts the caudal spine or spines into the victim, producing a puncture wound or
jagged laceration. The integumentary sheath covering the spine is ruptured and venom is released into the
wound, along with mucus, pieces of the sheath, and fragments of the spine. On occasion the entire spine tip is
broken off and remains in the wound .
Thus, a stingray wound is both a traumatic injury and an envenomation. The former involves the
physical damage caused by the sting itself. Because of the retrorse serrated teeth and powerful strikes,
significant lacerations can result. Secondary bacterial infection is common. Osteomyelitis may occur if the
bone is penetrated. Most injuries occur when the victim steps on a ray; another common cause is handling a
ray during its extraction from a fishing net or hook. The lower extremities, particularly the ankle and foot, are
involved most often, followed by the upper extremities, abdomen, and thorax. In a rare case, the heart was
directly injured. Fatalities have occurred after abdominal or thoracic (cardiac) penetration, and from
exsanguination from the femoral artery. Another death has been attributed to tetanus complicating a leg
wound. A spine partially or totally denuded of its sheath and venom glands may not necessarily cause an
envenomation.
The envenomation classically causes immediate local intense pain, edema, and variable bleeding. The
pain may radiate centrally, peaks at 30 to 60 minutes, and may last for up to 48 hours. The wound is initially
dusky or cyanotic and rapidly progresses to erythema and hemorrhagic discoloration, with rapid fat and
muscle hemorrhage and necrosis. If discoloration around the wound edge is not immediately apparent, within
2 hours it often extends several centimeters from the wound. Minor stings may simulate bacterial cellulitis.
Systemic manifestations include weakness, nausea, vomiting, diarrhea, diaphoresis, vertigo, tachycardia,
