Butler’s Frogfish, Tathicarpus butleri
The Butler’s Frogfish (Tathicarpus butleri), known also as the blackspot anglerfish, is a rare species of frogfish belonging to the family Antennariidae. The only member of its genus, this species is the most derived member of its family, representing a separate lineage from all other frogfishes, leading to some consideration of it being placed in its own family. It can be found off the southern coast of New Guinea, and along the coasts of Western Australia, the Northern Territory, and Queensland. As a benthic species, it inhabits inshore tropical waters and coral reefs to a maximum depth of 475 feet, though the majority of found in shallower waters of 150 feet. Its specific epithet honors its discoverer Dr. Graham Butler.
It can achieve a maximum length of 4 inches. It has a stout and laterally compressed body with a large head longer than it is deep. Like other anglerfishes, the first dorsal fin ray is modified into a lure for attracting their prey. The illicium of the Butler’s Frogfish is very long, measuring 24 to 47 percent the standard length and lacks the dermal spines. At the tip is a distinct esca that might measure 22 percent of the standard length, consisting of a thin and broad appendage covered with hair-like filaments and featuring 1 to 2 dark colored spots at the base. The mouth is protrusible, with many slender and sharp teeth on the jaws, vomer, and palantines. The dorsal and anal fins are tall, containing 10 to 11 and 7 fin rays respectively; the caudal fin is long and has 9 rays.
The frogfish has abnormally long and “arm-like” pectoral fin lobes, which unlike other frogfish are largely detached from the sides of the body. Its genus name, Tathicarpus, meaning “extending wrist”, is in reference to this trait. The fish utilizes these pectoral fins to clamber along the bottom of the sea. The number of pectoral fin rays is reduced and the Butler’s Frogfish can move each ray individually like “fingers” to stabilize or to hold onto objects. The pelvic fins contain 5 rays each and are positioned beneath the body. The skin is densely covered with bifurcate spinules; there are also varying numbers of large and fringed filaments over the body and the head. The coloration ranges from pale gray to greenish to brown, with darker colored markings. The fin membranes are thin and translucent.