Sargassum fish

The sargassum fish, also called the anglerfish or frog fish, is a marine ray-finned fish and the sole member of the genus Histrio, within the frogfish family Antennariidae. It inhabits floating mats of Sargassum seaweed in subtropical oceans. Its scientific name, Histrio histrio, comes from the Latin for "stage player" or "actor," a reference to its feeding behavior.

First formally described by Carl Linnaeus in 1758, with the Sargasso Sea given as its type locality, the species was later placed in its own genus, Histrio, by Johann Gotthelf Fischer von Waldheim in 1813. Within the Antennariidae, its closest relative is the deepwater frogfish. Some classifications put it in the subfamily Antennariinae, but the 5th edition of Fishes of the World does not recognize subfamilies, placing the family in the suborder Antennarioidei of the order Lophiiformes.

Etymology

The binomial Histrio histrio is tautonymous—both genus and species names are the same. Histrio means "harlequin," which Linnaeus may have chosen for the fish's gaudy appearance: its head, body, and fins are marked with streaks, spots, and lines in varied colors and patterns, and its skin bears appendages.

Description

This strange-looking fish is laterally compressed and reaches up to 20 cm in length. Its body and large mouth vary in color but are typically mottled and spotted with yellow, green, and brown on a lighter background, with fins often showing dark streaks or bands. It can change color rapidly from light to dark.

The body and fins are covered with weed-like protrusions, but the skin is otherwise smooth, lacking dermal spines. The dorsal fin has three spines and 11 to 13 soft rays; the front spine is modified into a slender growth on the upper lip called an illicium, tipped with a fleshy lump (the esca). No gill slits are visible—the gills open as pores near the base of the pectoral fins.

The anal fin has no spines and 7 to 13 soft rays. The pelvic fins are large, and the pectoral fins have 9 to 11 rays, are stalked, and can grip objects. The outer tail fin rays are simple, while the central ones are forked.

Distribution and habitat

The sargassum fish has a cosmopolitan distribution in tropical and subtropical seas, down to about 10 meters deep. It is found in parts of the Atlantic and Indo-Pacific where drifting seaweed accumulates. In the western Atlantic, it ranges from the Gulf of Maine to Uruguay.