Venomous Lionfish!

      

The lionfish (Pterois volitans) is a marine fish native to the Indo-Pacific region (Source). However, since the 1990s it has become common in other places around the globe due to the aquarium trade (Source). The P. volitans species is characterized by the red and white or brown and white stripes that cover the lionfish’s body and spines and serve as a warning to predators. Although beautiful, the sting of a lionfish is extremely painful and can lead to hospitalization for humans if they are stung (even by a dead lionfish!) On the spines (13 dorsal spines accompanied by 10-11 dorsal soft rays and 3 anal spines accompanied by 6-7 anal soft rays) glandular grooves are found extending from the base of the spine to approximately three quarters of the way up the spine (Source). These apocrine-type venom glands are triggered when the spine of the lionfish enters the body of a predator or threatening animal. This disturbs the gland tissue and causes the outer covering of the spine to push out ventrally, tearing through the glandular tissue and releasing the venom, which then travels up the glandular groove and into the body of the other creature (Source).

            Envenomation causes extreme pain and a range of cardiovascular, neuromuscular, and cytolytic (relating to the disruption of cells) effects in humans and can be fatal to other fish (Source). However, the venom glands were adapted for defense purposes and are not known to be used to capture or injure the lionfishs’ prey. While a few lionfish have been found in the stomachs of some grouper species, research has shown that even top predators, including sharks, and parasites avoid lionfish (Source). In addition, the mimic octopus has been known to mimic the lionfish, evidence that other marine animals are aware of and understand the danger of interaction with the lionfish. As a result, they continue to eat many smaller fish species and because the lionfish have no natural predators their numbers have been increasingly dramatically in the Atlantic (and in particular in the Bahamas). 

Consequently, the lionfish poses a threat to the future of the marine food chain in several areas and a danger to divers. Attempts to slow down the proliferation of lionfish include consumption (by humans), the sport of physically removing the lionfish from the water, and research to explore what it is in the Indo-Pacific region that keeps the lionfish population at a reasonable and sustainable level (Source).

While the adaption of these venomous spines is for defensive purposes it would be interesting to note how often the lionfish actually uses this mechanism and how often its appearance and reputation protect it from potential threat.