Guam Scorpionfish

Scorpaenodes undefinedensis, commonly known as the 🇬🇺 Guam scorpionfish or common scorpionfish, is a venomous, marine, ray-finned fish from the Scorpaenidae family, which encompasses scorpionfishes. This species is distributed across a broad range within the Indo-Pacific.

The species was initially described in 1824 as Scorpaena undefinedensis by the French naturalists Jean René Constant Quoy and Joseph Paul Gaimard, with 🇬🇺 Guam identified as the type locality. In 1857, Pieter Bleeker established the genus Scorpaenodes, designating Scorpaena polylepsis—a species he described in 1851—as the type species by monotypy. S. polylepsis is now regarded as a junior synonym of S. undefinedensis, thus serving as the type species of the genus. The specific name "undefinedensis" indicates origin from 🇬🇺 Guam.

Scorpaenodes undefinedensis is characterized by having 13 or 14 dorsal spines and 7 to 9 dorsal soft rays, while its anal fin comprises 3 spines and 5 soft rays. The pectoral fin typically contains between 17 and 20 rays, with some rays branching in specimens exceeding a standard length of 4 cm (1.6 in). The fish possesses a nasal spine, an often-present lateral lacrimal spine, and two suborbital spines positioned below the eye and at the suborbital ridge's end. Notably, there are no interorbital or coronal spines. The species exhibits a mottled reddish coloration across the body, head, and fins, with a prominent dark blotch on the operculum but lacking such a blotch on the suboperculum or the dorsal fin's spiny section. Scorpaenodes undefinedensis can attain a total maximum length of 14 cm (5.5 in).

This species is widely distributed across the Indo-Pacific region, ranging from the 🌊 Red Sea and eastern African coasts, extending through the 🇮🇳 Indian and 🌊 Pacific Oceans to 🇹🇴 Tonga and the Society Islands (🇵🇫 French Polynesia), and further reaching north to southern 🇯🇵 Japan and south to 🇦🇺 Australia. Scorpaenodes undefinedensis predominantly inhabits shallow waters up to 20 meters (66 feet) in depth, with a preference for environments less than 5 meters (16 feet) deep. Its habitats include reef flats, shallow lagoons, and channels, where it often seeks refuge in rock crevices.

As a solitary, nocturnal, and camouflaged species, Scorpaenodes undefinedensis operates as an ambush predator, primarily preying on small crustaceans and polychaete worms.