Pterois, commonly known as lionfish, is a genus of venomous marine fish found mostly in the Indo-Pacific. Pterois is characterized by red, white and black bands, showy pectoral fins and venomous spiky fin rays. Pterois are classified into nine different species, but Pterois radiata, Pterois volitans and Pterois miles are the most commonly studied. Pterois are popular aquarium fish and are readily utilized in the culinary world.
In the mid 1990s, the species P. volitans and P. miles were unintentionally introduced into the Atlantic Ocean and have become an invasive species along the East Coast of the United States, the Mesoamerican Barrier Reef System, and the wider Caribbean. They are now also found in the Gulf of Mexico.
Pterois range in size from 6.2 to 42.4 cm with typical adults measuring 38 cm and weighing an average of 480 g. They are well known for their ornate beauty, venomous spines and unique tentacles. Juvenile lionfish have a unique tentacle located above their eye sockets that varies in phenotype between species. It is suggested that the evolution of this tentacle serves to continually attract new prey; studies also suggest that it plays a role in selection.
Pterois can live from five to fifteen years and have complex courtship and mating behaviors. Females release two mucus-filled egg clusters frequently, which can contain as many as fifteen thousand eggs. Studies on Pterois reproductive habits have increased significantly in the past decade.
According to a study that involved the dissection of over 1,400 lionfish stomachs from Bahamian to North Carolinian waters, Pterois prey mostly on small fish, invertebrates and mollusks in large amounts, with some specimens’ stomachs containing up to six different species of prey. The amount of prey in lionfish stomachs over the course of the day suggest that lionfish feed most actively from 7:00–11:00 am, with decreased feeding throughout the afternoon. Lionfish are skilled hunters, using specialized bilateral swim bladder muscles to provide exquisite control of location in the water column, allowing the fish to alter its center of gravity to better attack prey. The lionfish then spreads its large pectoral fins and swallows its prey in a single motion. Researchers have also noted that lionfish blow jets of water while approaching prey, apparently in order to disorient them.
Aside from instances of larger lionfish individuals engaging in cannibalism on smaller individuals, adult lionfish have few identified natural predators. This is likely due to the effectiveness of their venomous spines. Moray eels (family Muraenidae), bluespotted cornetfish (Fistularia commersonii) and large groupers, like the tiger grouper (Mycteroperca tigris) and Nassau grouper (Epinephelus striatus), have been observed preying on lionfish. It remains unknown, however, as to how commonly these predators prey on lionfish. Sharks are also believed to be capable of preying on lionfish with no ill-effects from its spines. Park officials of the Roatan Marine Park in Honduras have attempted to train sharks to feed on lionfish as of 2011 in an attempt to control the invasive populations in the Caribbean. Predators of larvae and juvenile lionfish remain unknown, but may prove to be the primary limiting factor of lionfish populations in their native range.
Parasites of lionfish have rarely been observed and is assumed to be infrequent. They include isopods and leeches.
Lionfish are known for their venomous fin rays, a feature that is uncommon among marine fish in the East Coast coral reefs. The potency of their venom makes them excellent predators and poisonous to fishermen and divers. Pterois venom produced negative inotropic and chronotropic effects when tested in both frog and clam hearts and has a depressing effect on rabbit blood pressure. These results are thought to be due to nitric oxide release In humans, Pterois venom can cause systemic effects such as extreme pain, nausea, vomiting, fever, breathing difficulties, convulsions, dizziness, redness on the affected area, headache, numbness, paresthesia (pins and needles) and sweating. Rarely, such stings can cause temporary paralysis of the limbs, heart failure and even death. Fatalities are commonly in very young children, the elderly, those with a weak immune system or those who are allergic to their venom. However, their venom is rarely fatal to healthy humans. But some species have enough venom to produce extreme discomfort for over a period of several days. However, Pterois venom can provide a danger to allergic victims because some victims may experience anaphylaxis which is a serious and often life threatening that requires immediate emergency medical treatment. Severe allergic reactions to Pterois venom are usually chest pain, severe breathing difficulties, a drop in blood pressure, swelling of the tongue, sweating, runny nose, or slurred speech. Such reactions can be fatal if not treated.
The lionfish is a predator native to the Indo-Pacific. It aggressively preys on small fish and invertebrates. They can be found around the seaward edge of reefs and coral, in lagoons, and on rocky surfaces to fifty meters. They show a preference for turbid inshore areas and in harbors. Lionfish have a generally hostile attitude and are territorial towards other reef fish. Many universities in the Indo-Pacific have documented reports of Pterois aggression towards divers and researchers