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Some of the reef's most beautiful animals have deadly serious defenses. Here's what to watch out for on your next dive.


Modern scuba divers, like some of our ancestors, are fascinated by the underwater realm. Part of that allure is fed by our imaginations, which peer into the sea and, perhaps, conjure up strange sea monsters. Though these ferocious beasts are mostly make believe, the sea is filled with creatures that appear harmless but are capable of inflicting injury.

Sharks are the most well-known of marine perils, despite the fact that they rarely harm people. Far more common are the animals which possess a spine through which they are able to deliver a venom.

The underwater photographer who has backed into a cluster of sea urchins or the diver who places a hand on the perfectly camouflaged scorpion fish is not likely to have a fatal outcome, but is certainly going to be uncomfortable for a while. We will consider similar encounters in this article and limit ourselves to injuries produced by animals with spines.

Spines are adapted by animals for various purposes. They are generally used for protection, although propulsion and gathering prey are frequently the tasks of specialized spines. Spines may be concealed or highlighted; slashing or penetrating; and venomous or non-venomous. Some are fragile, needle-like in size and sharpness, while others are large and strong with recurved teeth.

Animals in several phyla possess spines which are alike in the principle of operation, but differ in location, size, potency of venom and degree of hazard to the diver. We will start with some of the invertebrate animals and examine the characteristics and functions of spines found in this group.

Spiny invertebrates
The echinoderms are radially symmetrical animals with usually five arms or radii and have a more or less rigid skeleton embedded in the body wall. The starfish and sea urchins belong to this phylum, and there are a few species of interest to divers. There are two known venomous starfishes: the Acanthaster planci (crown of thorns) and Acanthaster elissi of the Indo-Pacific and eastern Pacific regions respectively. The outer surface of the body is covered by large, sharp spines which are soft calcareous structures that break off on penetration and are difficult to remove. Glands in the animal's skin produce a venom which causes a severe inflammatory response in humans consisting of redness and swelling, associated with vomiting, numbness and, rarely, paralysis.

Sea urchins are equipped with spines which vary greatly among species. The spines in some species are long, hollow, slender and needle sharp. The sharpness permits them to penetrate easily and then break because of their brittleness. A venom accompanies the spines in some species and penetration of the spine may immediately result in a burning sensation followed quickly by redness, swelling and aching. More serious symptoms of numbness and paralysis have been reported as well as infection which is common.

There are many hazardous sea urchin species, and they all produce similar symptoms. A few typical species are these: Toxopneustes pileous is the felt cap sea urchin found in the Indo-Pacific region. Two closely related species are Toxopneustes elegans of Japan and T. roseus of the eastern Pacific. The common long-spined or hairy sea urchin Diadema setosum is found throughout the Indo-Pacific and West Indies and accounts for many injuries.

Stingrays & dogfish
In 1608 Capt. John Smith grounded his ship in the Rappahanock River while exploring Chesapeake Bay. While waiting for the tide to refloat his ship, he went flounder gigging using his sword for a gig. Unfortunately he gigged a stingray, but did not know what type of animal he had encountered. As he removed the stingray from his sword, he received a sting on the wrist. The venom made him very sick, and in fact he was certain that he would not recover. Preparations were made for his death, even to the extent of a grave being prepared. However, treatment with a hot oil relieved his symptoms, and he enjoyed the stingray for supper. The island still bears the name Stingray Isle because of that incident.

Capt. Smith was not the first - nor will he be the last - person in North America to be stung by a ray. There are estimates of more than 1,500 injuries per year in the United States from this animal.

Stingrays are found in tropical to warm temperature seas. Their favorite habitat is a sandy area, a shoal or river mouth in shallow water. They lie on top of the sand or partially burrowed with only the eyes, gill slits and tails visible. The stinging spine is part of the tail and situated near the base. The spine is made of a hard material and has sharp, recurved teeth along either side. There are deep grooves on the underside of the spine where the venom glands are located. The spine is covered by an integumentary sheath which protects the stinging organ.

Most injuries occur when a victim steps on an unsuspecting stingray lying in the sand resulting in a defensive move by the stingray. The injury begins as a puncture wound when the spine penetrates the skin and then becomes a jagged laceration as the spine is withdrawn and the recurved teeth inflict further injury while venom is injected into the wound. The sheath remains behind in fragments in the wound so that the wound contains a foreign body (the sheath), a venom, seriously damaged tissue and inevitably bacterial contamination. The result is a complicated injury that requires extensive treatment and a prolonged healing time. A few deaths have occurred when the spine penetrated either the chest or abdomen of a child falling on the animal.

The dogfish is a relative of the stingray that is also equipped with some formidable defenses. The spiny dogfish Squalus acanthias is known to have injured humans. In fact, there is a reference dating from 200 A.D. in a Grecian fishing poem: "Dogfish, from their prickly mail, well-named the spinous; These in punctures sharp, a fatal poison from their spines inject." This animal inhabits the North Atlantic and North Pacific. They have a single spine at the anterior margin of each of the two dorsal fins. When the spine enters the skin, venom enters from the venom gland located on the upper portion of each spine.

Ratfish, catfish & weeverfishes
The ratfishes (Chimaera) are a group of cartilaginous fishes. They have two dorsal fins, the second of which has a sharp spine at the anterior edge which delivers a venom. The Chimaera prefer cold water and are found from the surface down to 9,900 feet / 3,000 meters. These animals inflict a very painful sting with immediate pain increasing in intensity before gradually decreasing and then persisting for days. The area around the wound becomes numb and blue with the appearance of a severe inflammatory reaction.

Catfish are a large group of species, most of which are freshwater with a few marine species. There is a single, strong, needle-sharp spine located in front of the dorsal and pectoral fins. The spine is covered by an integumentary sheath which contains the venom glands. In a few species there are recurved teeth along the spine which can lacerate a wound enhancing venom absorption and increasing the likelihood of infection. Two common freshwater species in the United States are the "Catfish" (Galeichths felis) and the Carolina madtom (Noturus furiosus). The sea catfish (Bagre marinus) inhabits the east coast of the Americas from New England to Brazil.

The weeverfishes are small, attractive but aggressive marine fish with well developed venom apparatus. They may be a real danger to a diver. The weevers bury themselves in soft sand until they dart out rapidly to strike. They have a series of dorsal spines with venom glands producing a venom with neurotoxin and hemotoxin features. The pain from a sting is instant and rapidly becomes increasingly worse to reach excruciating levels. If not treated, the pain will subside in about 24 hours, although full recovery may take several days to months. There have been very severe reactions reported, including death.

The scorpionfishes (Scorpaenidae) are found worldwide in tropical and temperate areas. They can be divided into three main groups as follows: zebra fish (Pterois); scorpionfish (Scorpaena) and stonefish (Synanceja).

The zebra fish, also know as turkey fish or lionfish, are beautiful, ornate coral reef fishes usually found in shallow water hovering over a crevice or resting on a fixed object. They are fearless, and grabbing one of these fish can result in an extremely painful experience.

The scorpionfish (Scorpaena) and stonefish (Synaceja) are shallow water dwellers and may be found on sandy bottoms, rocks or coral reefs. Their protective camouflage coloring makes them extremely difficult to see, and accidental encounters are common.

The spines of the three groups differ somewhat, but all deliver a venom. The stonefish is perhaps the most dangerous, as its spines are very strong and capable of penetrating a boot while delivering a potent venom. Fatalities have occurred from the sting of stonefish.

With the exception of the stonefish, the symptoms of a sting are pretty much the same for all species. Identification of the responsible fish may not be possible, but there is no great variety in symptomatology regardless of the species responsible. There is immediate pain with increasing intensity and a cyanotic wound which remains the same for several hours and then begins to improve.

The sting of the stonefish, however, produces excruciating pain sometimes with paralysis of the limb. There may be life threatening symptoms of heart failure, delirium, seizures, respiratory distress and death has occurred.

The clinical features of stonefish envenomation include the following:

  1. Local pain increasing in intensity over a few minutes and lessening after a few hours
  2. One or more puncture wounds
  3. Puncture site anesthetized
  4. Site inflamed and sometimes cyanotic
  5. Surrounding area hypersensitive, pale, swollen
  6. Regional lymph nodes tender and painful
  7. Generalized symptoms are sometimes severe with distress disproportionate to the clinical signs
  8. There is frequently malaise, nausea and vomiting, sweating, delirium
  9. Temperature elevation
  10. Cardiovascular shock
  11. Respiratory distress
  12. Death may occur

Recovery may require many months. There is an antivenin available for stonefish stings from Commonwealth Serum Laboratories in Melbourne, Australia.

Toadfish, tangs & other spined fishes
The numerous species of toadfishes (Batrachoididae) are small bottom fishes that inhabit most of the warm-water coastal areas of the world. They are ugly (except, possibly, to other toadfish) with broad, depressed heads and a large mouth. They have two dorsal fin spines with venom glands and another spine located in the gill cover. Anglers are the frequent victims of a sting when they attempt to remove a hooked fish from their line. The pain is similar to that of the scorpion fish and develops rapidly with intense pain followed by swelling, redness and heat. There are no recorded fatalities, and the symptoms subside within a few days.

The surgeonfishes (Acanthuridae), also called tangs, have a spine near the tail resembling a scalpel. If the fish is threatened, it extends the spine and lashes out with its tail. Contact with the spine can produce a deep, painful laceration. There is no venom associated with this spine. There are other fish with venomous spines capable of producing wounds in divers. These include the flying gunard (Dactylopterus volitans); sea robin (Trigla lyra); dragonet (Callionumus lyra); rabbitfish (Siganus doliatus); scats (Scatophagidae sp.); stargazers (Uranoscopus sp.) and leatherbacks (Carangidae sp.).

The wounds produced by the various species of animals with a venomous spine have common features. The wounds are frequently lacerated puncture wounds which contain foreign material, a venom and bacterial contamination.

The basic principles of wound care apply to these injuries after initial evaluation and stabilization of the victim. It is important to relieve pain as promptly as possible and to cleanse the wound of all foreign material using sterile technique if available. Irrigation of the wound may remove venom as well as portions of the integumentary sheath, slime, sand, etc. If any foreign material remains, healing will be delayed or may not occur. Many of these venoms are heat labile and a hot soak (115 F / 45 C) at as high a temperature as tolerated should be tried for 30-90 minutes.

The care of these wounds can be summarized as follows:

  1. Rest affected area in elevated position
  2. Immerse wound in 45 C water for 30-90 minutes or until pain is relieved and does not recur
  3. Local anesthetic infiltration if needed for pain relief - no epinephrine
  4. Systemic analgesics or narcotics rarely needed
  5. Resuscitation as needed
  6. General wound care including antibiotics if indicated
  7. Foreign body removal

Some of these wounds will be severe either due to the size of the animal (stingray) or the potency of the venom (stonefish). The stingray wound may require surgical exploration and debridement to remove foreign material and damaged tissue. The stonefish injury may require the administration of an anti-venom, which itself may be hazardous.

Victims of these injuries should be treated at a local medical facility, the sophistication of which will depend on the location of the diving area. Divers Alert Network frequently can assist in advice concerning immediate care of these injuries and referral to appropriate medical centers. DAN members, of course, can be evacuated at no cost to them if that is indicated medically.

Prevention is accomplished by avoiding contact with the animal, which sounds simple, but may not be in conditions of poor visibility, currents, confined areas or other environmental limitations. Divers should not attempt to handle, tease, feed or annoy any marine animal. Exploring a crevice with your hand is a good way to receive an injury from a concealed animal defending itself. Do not allow a current to force you against a fixed object which may be covered with hostile critters. Protective clothing is very important. Make an effort to find out which animals you may encounter in your dive, and learn about their characteristics and habitats before you begin the dive.

(c) January/February 1995 Alert Diver. At the time of this writing, G. Yancey Mebane, M.D., was the Associate Medical Director of Divers Alert Network.