As a part of the A-Z Photographic Glossary of Biological Terms challenge, today it is I for Invasive, as illustrated by this Red Lionfish (Pterois volitans), from Bonaire in the Dutch Caribbean.
It is important here to first distinguish between terms that are often, and erroneously, used interchangeably. Usually when one refers to “invasive species” the implication is that it is also a non-native, however there are instances where a native or indigenous species can also be considered invasive by spreading outside its historical range, attaining extreme abundances, or exerting severe effects upon another native species as a result of predation or competition. Quite often the term “introduced” or “alien” is used to denote a species that is non-native, but again several introduced species do not threaten to become invasive or unmanageable nor do they adversely affect native species, although as we discuss below, it is certainly probable.
Using two terms together, such as “introduced invasive” or “invasive alien” or “non-native invasive”, or in the case of a native species spreading outside its normal range, a “native invader” makes it more precise.
All twelve species of Lionfish are venomous fish native to the Indo-Pacific but now two of them, the Red Lionfish pictured above, and the Common Lionfish (Pterois miles), are non-native invasive species throughout the Caribbean; in less than a decade these invasive aliens have become established along the Southeast US and the Caribbean and are now expanding into the Gulf of Mexico and South America; they are not only established, they are thriving, and at the expense of native species. With very few natural predators and as voracious feeders, they have outcompeted and now filled the niche of the overfished snapper and grouper, and they reproduce rapidly, around 20,000 eggs every 4 days!
When hunting, they corner prey using their large fins, then use their quick reflexes to swallow the prey whole. Their venom is in the spines on their dorsal fin, and as here, when threatened they face the threat, move upside down, bringing their spines to bear. They are actually somewhat difficult to photograph as they are often hiding in ambush under coral overhangs and require “prompting” to emerge, and one has to avoid their venomous spines or else you’re in for a nasty sting that an cause breathing difficulties and convulsions, not exactly what one needs when diving at at depth!
Red Lionfish (Pterois volitans) with Whitestar Sheet Coral (Agaricia lamarcki), Bonaire, Dutch Caribbean