into three groups typified by different genera on the basis of venom organ structure: (1) Pterois (zebrafish,
lionfish, and butterfly cod), (2) Scorpaena (scorpionfish, bullrout, and sculpin), and (3) Synanceja (stonefish).
Other venomous fish that sting in a manner similar to scorpionfish include the Atlantic toadfish (family
Batrachoididae and genus Thalassophyrne), with two venomous dorsal fin spines, and the Pacific ratfish
(Hydrolagus colliei) and European ratfish (Chimaera monstrosa), both with a single dorsal venomous spine.
Toadfishes hide in crevices and burrows, under rocks and debris, or in seaweed, sand, or mud. They may
change coloration rapidly and remain superbly camouflaged. Rabbitfishes (family Siganidae) and leatherjacks
(leatherbacks or leatherjackets: family Carangidae) carry venomous spines or fins and pose additional risks.
Stargazers (family Uranoscopidae) have spines, but do not appear to be venomous.
For lionfishes, scorpionfishes, and stonefishes, the venom organs are the 12 or 13 (of 18) dorsal, 2
pelvic, and 3 anal spines, with associated venom glands. Although they are frequently large, plumelike, and
ornate (lionfishes), the pectoral spines are not associated with venom glands. Each spine is covered with an
integumentary sheath, under which venom filters along grooves in the anterolateral region of the spine from
the paired glands situated at the base or in the midportion of the spine. It is estimated that the two venom
glands of a dorsal stonefish spine carry 5 to 10 mg of venom, closely associated with antigenic proteins of
high molecular weight (between 50,000 and 800,000).
Pterois species carry long slender spines with small venom glands covered by a thin integumentary sheath.
Scorpaena species carry longer heavy spines with moderate-sized venom glands covered by a thicker
integumentary sheath. Synanceja species carry short, thick spines with large, well-developed venom glands
covered by an extremely thick integumentary sheath. However, the skin over the venom gland is loosely
attached, so when a human treads on the fish, the skin is pushed down the spine and the venom gland is
compressed by the crumpled sheath. The pressure forces the venom gland to empty up the paired narrow
ducts, so that venom and glandular tissue spurt into the wound.
When any of these fish is removed from the water, handled, stepped on, or otherwise threatened, it
reflexively erects the spinous dorsal fin and flares out the armed gill covers and pectoral and anal fins. If
provoked while still in the water, it actually attacks. The venom is injected by a direct puncture wound
through the skin, which tears the sheath and may fracture the spine, in a manner analogous to that of a
stingray envenomation.
The presentation of the injury is similar to that of the stingray envenomation, in that the unwary diver
or fisherman steps on or handles the fish. In the United States, marine aquarists and beneficiaries of illegal
importation of tropical animals are increasingly envenomed as they unknowledgeably handle Pterois volitans,
P. radiata, or Scorpaena guttata. In Indo-Pacific waters, envenomations of the foot and lower extremity are
more commonly caused by the stonefish, such as Synanceja horrida, S. trachynis, or S. verrucosa.
Scorpionfish stings vary according to the species, with a progression in severity from the lionfish (mild)
through the scorpionfish (moderate to severe) to the stonefish (severe to life threatening).
The severity of the envenomation depends on the number and type of stings, species, amount of
venom released, and age and underlying health of the victim. Pain is immediate and intense, with radiation
centrally. Untreated, the pain peaks at 60 to 90 minutes and persists for 6 to 12 hours. With a stonefish
envenomation, the pain may be severe enough to cause delirium and may persist at high levels for days. The
wound and surrounding area are initially ischemic and then cyanotic, with more broadly surrounding areas of
erythema, edema, and warmth. Vesicles may form. Rapid tissue sloughing and close surrounding areas of
cellulitis, with anesthesia adjacent to peripheral hypesthesia, may be present within 48 hours. Necrotic
ulceration is rare, but may occur, following a lionfish envenomation. Severe local tissue reaction is more
common following the sting of a scorpionfish or stonefish. Systemic effects include anxiety, headache,
tremors, maculopapular skin rash, nausea, vomiting, diarrhea, abdominal pain, diaphoresis, pallor,
restlessness, delirium, seizures, limb paralysis, peripheral neuritis or neuropathy, lymphangitis, arthritis, fever,
hypertension, respiratory distress, bradycardia, tachycardia, atrioventricular block, ventricular fibrillation,
congestive heart failure, pericarditis, hypotension, syncope, and death. Pulmonary edema is a bona fide
sequel. Death in humans, which is extremely rare, usually occurs within the first 6 to 8 hours. The wound is
indolent and may require months to heal, only to leave a cutaneous granuloma or marked tissue defect,
particularly after a secondary infection or deep abscess. Mild pain may persist for days to weeks. After
successful therapy, paresthesias or numbness in the affected extremity may persist for a few weeks.
