Lophiiformes

(Anglerfishes)

Class Actinopterygii

Order Lophiiformes

Number of families 18

Evolution and systematics

The anglerfishes (order Lophiiformes) are a remarkable assemblage of approximately 65 genera and nearly 300 species of curious and wonderfully bizarre fishes. Lophiiformes is one of six orders that make up the euteleostean superorder Paracanthopterygii. Of the six paracanthopterygian orders, the toadfishes (order Batrachoidiformes) are considered to be most closely related to the anglerfishes. The fossil record extends back to the Eocene, with representatives from the families Antennariidae and Lophiidae having been found in Eocene formations of Italy.

Pietsch and Grobecker recognized 18 lophiiform families and divided them among five suborders. In phylogenetic order and from most primitive to most dervied, they are: Lophioidei (containing only one family, Lophiidae, the monkfishes), Antennarioidei (four families, the frogfishes), Chaunacoidei (one family, Chaunacidae, the sea toads or coffinfishes), Ogcocephaloidei (one family, the batfishes), and Ceratioidei (11 families, the bathypelagic anglerfishes).

Physical characteristics

The anglerfishes share two very conspicuous derived characters (synapomorphies). (1) The anterior portion of the spinous dorsal fin has migrated forward to a position on the anterior surface of the head, just behind the snout. The first dorsal fin spine has been modified further to serve as an angling apparatus (illicium), by loosing its membranous connection to the other cephalic dorsal fin spines and acquiring a distal bait or lure (esca) to help attract prey. (2) The bases of the pectoral fins (radials) have become greatly elongated so that the pectoral fins appear to be at the end of long, jointed arms. The number of pectoral radials has been reduced to between two and five. Additional lophiiform synapomorphies are gill openings that are reduced in size and, in all but the most primitive lophioids, located posterior to the pectoral fin base; five or six branchiostegal rays; absent ribs; and first vertebra fused to the neurocranium. Anglerfishes are very diverse in both color and size; this order ranges from a few inches to approximately 6.6 ft (2 m) in length.

Distribution

Anglerfishes are worldwide in distribution. With the exception of one antennariid (frogfish) species that has been known to enter freshwater, they are exclusively marine, and most species occur in deep water.

Habitat

Most anglerfishes occur in deep oceanic waters. The ceratioid anglerfishes are midwater fishes, inhabiting primarily the mesopelagic and bathypelagic zones. Most other anglerfishes are benthic and occur in the waters of the outer continental shelf and continental slope. A few lophioids enter the shallows at high latitudes, and many antennarioids occur in coral reef or other shallow habitats in tropical and warm temperate waters.

Behavior

Most knowledge of anglerfish behavior is associated with the specialized adaptations that have made them such effective and successful ambush predators. Most important among them are the angling apparatus and the functional morphological features of the feeding mechanism. These adaptations, along with certain reproductive adaptations, have made the anglerfish among the most successful predators in the deep sea.

The angling apparatus (illicium) is derived from the anteriormost spine in the dorsal fin. The illicium and second dorsal fin spine (if present) articulate with a single, enlarged pterygiophore. The illicium has a rather elaborate set of associated muscles, which allows the angler to move the spine rapidly, thus thrashing the bait (esca) vigorously above or in front of the mouth. In some anglerfishes the bait may be a simple bulb or clublike structure, but in others it can be quite

elaborate. In many deep-sea species, the esca is bioluminescent, while in forms that live in sunlit regions, it may be an elaborate fleshy structure, occasionally resembling a small, shrimplike crustacean in some lophiid species or even a small fish in one species of antennariid.

The mouth in most anglerfishes is cavernous, and in many species it is lined with long, sharp, thin, depressible teeth. The functional morphological features associated with the anglerfish feeding apparatus are quite fascinating. Like many derived teleostean fishes, anglerfishes are "gape-and-suck" feeders. Many anglerfishes, however, have a greatly elongated and highly mobile suspensorium, or hyopalatine arch (the portion of the skull that supports the lower jaw). This feature serves to permit swallowing of very large prey and allows the volume of the buccal cavity to increase to a much greater extent than in other fishes, which results in much greater negative pressure or suction when the mouth is opened rapidly.

Not only can anglerfishes create much greater negative pressure when opening the mouth and expanding the buccal cavity, but they appear to be capable of doing so much more rapidly than other fishes. Pietsch and Grobecker used high-speed cinematography (800 and 1,000 frames/second) to study the functional morphological characteristics of the feeding apparatus in antennariid anglerfishes. They showed that maximum oral expansion and subsequent prey engulfment may occur in as little as four milliseconds, and the average speed for three species of Antennarius was seven milliseconds. For comparison, this takes 40 milliseconds in the European perch (Perca fluviatilis), 16 milliseconds in the freshwater butterflyfish (Pantodon buchholzi), and 15 milliseconds in the stonefish (Synanceia verrucosa).

During typical ambush feeding, the anglerfish remains motionless (either on the bottom or in the water column, depending on the family) until suitable prey is detected. Many benthic anglerfishes (e.g., antennariids and lophiids) are capable of remarkable cryptic coloration, whereas the midwater forms are usually very dark brown or black (cryptic in a pelagic environment with little or no light). Upon sensing prey, the angler brings the illicium into play, attempting to attract the prey to within reach (aggressive mimicry). When

the prey reaches the strike zone, the mouth of the angler opens rapidly, and the buccal cavity expands greatly, creating a strong suction that draws in the prey.

Feeding ecology and diet

Anglerfishes feed primarily upon nekton, especially fishes and other nektonic organisms that probably are attracted by angling apparatus. Batfishes are one of the few groups of anglerfishes that feed primarily on benthic invertebrates. There is evidence suggesting that various kinds of anglerfishes—including large species—are consumed by larger predatory fishes such as sharks.

Reproductive biology

Very little is known about the reproductive biology and early life history of most anglerfishes, but it would appear that the early larval stages of all anglerfishes are pelagic, and thus meroplanktonic. One adaptation that does appear to be common to all anglerfishes is the acquisition of sexual dimorphism in the size and structure of the olfactory organs. This appears to be associated with the production of species-specific pheromones by the females, which attract the males during the breeding season. What little else is known about the reproductive biology of these fishes is restricted primarily to the families Lophiidae, Antennariidae, and a few ceratioid families; within these families, knowledge is likewise restricted to very few species.

Early life-history stages have been described for a few of the 25 species of lophiid anglerfishes (Lophius americanus, L. budegassa, and L. piscatorius). Larvae of only four of the 41 antennariid species have been described, but only Antennarius striatus and Histrio histrio are reasonably well known.

In the case of all anglerfishes from which eggs have been identified, eggs are released from the female embedded in a long, bouyant, ribbonlike mucoid veil. This is known to reach a length of 39.4 ft (12 m) and a width of 5 ft (1.5 m) and has been estimated to contain more than 1.3 million eggs in one large lophiid anglerfish species (L. americanus). The pigmentation of the embryos imparts a dark hue to the veil, and they are so conspicuous as they float at the surface of the sea that they have long been known to commercial fishermen. In anglerfishes in which the larvae have been identified, the larvae pass through a planktonic stage before becoming either benthic or nektonic (in the case of the midwater ceratioid anglerfishes).

Conservation status

Only one of the anglerfish families, Lophiidae, contains species of economic importance. These are harvested commercially in U.S., European, and Japanese waters, and the species that occurs off the Atlantic Coast of the United States, L. americanus, has received protection from the U. S. National Marine Fisheries Service owing to overfishing both for the meat, which is marketed in the United States as monkfish, and the liver, which is highly prized in Japan. The IUCN lists the spotted handfish (Brachionichthys hirsutus) of Tasmania as Critically Endangered. The population of this species has been greatly reduced by an introduced starfish that preys on its egg clusters.

Significance to humans

Other than the lophiid species that are harvested commercially, lophiiform fishes have little importance to humans.

Species accounts

List of Species

Big-eye frogfish

Antennarius radiosus

family

Antennariidae

taxonomy

Antennarius radiosus Garman, 1896.

other common names

English: Singlespot frogfish.

physical characteristics

The big-eye frogfish has skin with closely set, forked dermal spinules. The illicium is about as long as the second dorsal fin spine and has no dermal spinules. There is a single dark spot (ocellus) surrounded by a lightly colored ring below the posterior portion of the soft dorsal fin.

distribution

The big-eye frogfish occurs in the western Atlantic Ocean from Long Island, New York, to Florida and across the northern Gulf of Mexico. It has been reported from the eastern Atlantic, but it is apparently very rare there. It has been taken at depths ranging from 20 to 900 ft (6–275 m).

habitat

Like other members of its genus, the big-eye frogfish is benthic. This species is primarily an inhabitant of mud bottoms. It is commonly taken by shrimp trawlers in the northern Gulf of Mexico, and it is frequently found in deeper portions of higher-salinity estuaries.

behavior

Unknown.

feeding ecology and diet

Like other frogfishes and most other anglerfishes, the big-eye frogfish is a voracious ambush predator and will take any prey it can capture.

reproductive biology

Unknown.

conservation status

Not threatened. A significant death rate may result from those that are taken as bycatch by shrimp trawlers.

significance to humans

None known.

Sargassumfish

Histrio histrio

family

Antennariidae

taxonomy

Histrio histrio (Linnaeus, 1758).

other common names

English: Sea mouse, mousefish.

physical characteristics

Frogfishes (family Antennariidae) are somewhat similar to their monkfish relatives in that they have a large head on which are located several isolated dorsal fin spines; the pectoral fins appear armlike. They are strikingly different in that the head is globose and the body is flattened laterally (compressed) rather than dorsally (depressed). In addition, the second and third dorsal fin spines usually are surrounded by so much fleshy skin that it may be difficult to recognize them as fin spines. The second, or soft, dorsal and anal fins are much more conspicuous, and the soft dorsal is usually much longer than the anal fin. The sargassumfish is characterized by its very short angling apparatus and its smooth skin, which lacks the small, spiny scales or dermal spinules typical of most other frogfishes. Its color pattern is changeable and highly variable, but it is usually cryptic, consisting of streaks, spots, and mottling of brown, olive, and yellow, making it nearly impossible to detect among the sargassum weed in which it hides.

distribution

The sargassumfish has the widest geographic distribution of any frogfish. Being an obligate associate of sargassum weed, they are found wherever this species occurs, that is, in tropical, warm temperate, and occasionally cool temperate waters of the Atlantic, Pacific, and Indian Oceans. They appear to be very rare in the eastern Atlantic, and they are absent from the eastern Pacific.

habitat

The sargassumfish is the only frogfish species that is not benthic. It is only found associated with the epipelagic brown algae, Sargassum, in tropical and warm temperate environments. Although Sargassum is usually pelagic, members of the community associated with it, including the sargassumfish, are technically pseudopelagic.

behavior

Most of what is known about the behavior of sargassumfish is associated with their feeding. This behavior is described in the introductory section.

feeding ecology and diet

Like most other anglerfishes, sargassumfish are ambush predators that use aggressive mimicry to attract prey. Most observers describe them as particularly voracious, feeding readily and indiscriminately on anything they can swallow, including fishes as long as or longer than themselves. They even consume other sargassumfish. They are one of the major predators of the sargassum community.

reproductive biology

Reproduction in the sargassumfish is similar to the known reproductive behavior of other anglerfishes. The eggs are released in the typical egg veil or raft, which in sargassumfish may be 35–47 in (90–120 cm) long and 2–4 in (5–10 cm) wide.

conservation status

Not threatened.

significance to humans

None known.

Seadevil

Cryptopsaras couesii

family

Ceratiidae

taxonomy

Cryptosaras couesii Gill, 1883.

other common names

None known.

physical characteristics

Like other midwater anglerfishes, the seadevil is characterized by the absence of pelvic fins, pseudobranchs, and scales or other dermal derivatives. Moderate to extreme degrees of sexual dimorphism characterize members of this suborder. Ceratiids exhibit extreme sexual dimorphism, with the adult males being reduced to ectoparasites of the females. As with most species, the lure (esca) appears to be bioluminescent in the seadevil. Female seadevils have a vertical to strongly oblique mouth, and the first two or three rays of the soft dorsal fin are modified as caruncles (low, fleshy appendages).

distribution

Their distribution is worldwide between 63° N and 43° S latitudes.

habitat

The species inhabits the lower mesopelagic and bathypelagic zones, between 246 and 13,123 ft (75–4,000 m), but is most commonly found between 1,640 and 4,101 ft (500–1,250 m).

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Ceratioid anglerfishes, like the seadevil, are one of the most important groups of predatory fishes in the lower mesopelagic and bathypelagic zones of the world oceans. Feeding is by aggressive mimicry using the angling apparatus. They feed upon zooplankton and nekton, with fishes and cephalopods probably forming a major component of the diet.

reproductive biology

The reproductive adaptations found among the ceratioid anglerfishes are among the most fascinating in the animal kingdom. As mentioned earlier, all lophiiform anglerfishes appear to have some degree of sexual dimorphism in the structure and size of the olfactory organs. It is assumed that this is associated with the females' production of species-specific pheromones, which attract the males when the female is ready to breed. In ceratioid anglerfishes this sexual dimorphism has reached its extreme, not only among the vertebrates but also perhaps the entire animal kingdom. In most of the 11 ceratioid families, the female is considerably larger than the male (females range from three to 13 times the length of conspecific males). Furthermore, in at least four ceratioid families the males have been so drastically reduced that they have become essentially a pair of swimming testes directed by a huge pair of olfactory organs. Once these "minimized" males find a female, they attach themselves to her with their jaws, eventually achieving histological fusion and leading the remainder of their lives as essentially a pair of "ectoparasitic" testes.

conservation status

Not threatened.

significance to humans

None known.

Monkfish

Lophius americanus

family

Lophiidae

taxonomy

Lophius americanus Curvier and Valenciennes in Valenciennes, 1837, North America.

other common names

English: Goosefish, anglerfish.

physical characteristics

Like most lophiid anglerfishes, the monkfish is distinguished easily from other anglerfishes by its very large, wide, flattened head. Lophiids also have an enormous mouth armed with long, sharp, conical teeth, and the angling apparatus and second dorsal fin spine arise very close to each other at the anterior end of the snout. The monkfish has a number of derived character states, among which are increased numbers of dorsal and anal fin rays and vertebrae, gill openings restricted to a location completely behind the pectoral fin base, and a variety of cranial osteological features. The monkfish is distinguished from its congeners by several morphological characters.

distribution

The monkfish is known to occur from the Grand Banks off Newfoundland south to the east coast of Florida (about 29° N latitude) and from just below the tide line (only at high latitudes) to depths of more than 2,625 ft (800 m). However, few large individuals are taken below 1,312 ft (400 m). This is the only member of the genus found in the western Atlantic north of Cape Hatteras.

habitat

Adult monkfish have been found on soft and hard substrates including soft mud, soft sand, hard sand, pebbles, gravel, and broken shells.

behavior

Most of what is known about lophiid behavior comes from observations of the monkfish and another species, Lophius piscatorius; general aspects of this behavior are described earlier, in the ordinal account. Aristotle made the very first observations of angling behavior. He described them as having hairlike filaments hung before their eyes, with knobs attached like bait to the end of each filament. When little fishes come in range of the filaments and strike at them, they are led down with the filaments into the monkfish's mouth. Such observations were not recorded again until 1925, when Bigelow and Welsh reported the observations of W. F. Clapp, who observed monkfish catching young tomcod (Microgadus tomcod) in the eelgrass beds of Duxbury Bay, Massachusetts.

feeding ecology and diet

Like all lophiiform anglerfishes, monkfishes are voracious ambush predators. Their diet consists primarily of fishes, and when given a choice, they prefer soft-rayed fishes to spiny-rayed species. When the opportunity presents itself, however, they take any prey large enough to engulf. This includes fishes nearly as long as itself. The alternate name goosefish alludes to the fact that the monkfish has been known to engulf marine birds when it enters shallow coastal waters at high latitudes during the winter months. (Cormorants, herring gulls, widgeons, scoters, loons, guillemots, razor-billed auks, grebes, and other diving fowl, such as scaup ducks and mergansers, have all been recorded as stomach contents.) Smaller monkfishes are known to feed on a wide variety of invertebrates, including small lobsters, crabs, squid, and polychaetes.

reproductive biology

As mentioned earlier, the monkfish is one of the few lophiid species for which detailed life history information is available. Long, mucoid egg veils are characteristic of this species.

conservation status

During the latter few decades of the twentieth century, the popularity of monkfish increased steadily in U. S. markets. Because the liver also is highly sought by the Japanese market, fishing pressure on this species has resulted in overexploitation. Fortunately, this species has received some protection from the U. S. National Marine Fisheries Service. This species is not listed by the IUCN.

significance to humans

As Lophius americanus has gained popularity with consumers in the United States and there is strong demand for it in the Japanese market, this species has tremendous economic importance.

Longnose batfish

Ogcocephalus corniger

family

Ogcocephalidae

taxonomy

Ogocephalus corniger Bradbury, 1980.

other common names

None known.

physical characteristics

Most batfishes are dorsoventrally flattened. They have only a single, very short dorsal fin spine (the illicium), although the vestige of the second spine may be present but embedded. The illicium usually is contained within a deeply concave illicial cavity, and it typically extends forward and downward rather than forward and upward, as in most other anglerfishes. The skin is covered with prominent, tubercle-like scales, which may be very large and conical (bucklers) in some genera. The scales fuse at the anterior end of the snout, forming a moderate to greatly elongated rostrum. The mouth is relatively small compared with other anglerfishes and has small teeth. The longnose batfish has a long, slender rostrum at the end of a triangular head and dark bands of pigment on the distal portions of the pectoral and caudal fins. The overall body color is dark brown or gray, with small, pale spots uniformly distributed on the dorsal surface.

distribution

The longnose batfish inhabits the western Atlantic from Cape Lookout, North Carolina, south to the Yucatan Peninsula, including the Gulf of Mexico and the Caribbean. It has been taken at depths ranging from 95 ft (29 m) to 755 ft (230 m).

habitat

All batfishes are benthic, occurring on a wide variety of bottom types.

behavior

Unknown.

feeding ecology and diet

Batfishes feed using aggressive mimicry, as do most anglerfishes; however, they are unusual among anglerfishes in that a greater proportion of their diet seems to be small, benthic invertebrates.

reproductive biology

Unknown.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Collette, Bruce B., and Grace Klein-MacPhee, eds. Bigelow and Schroeder's Fishes of the Gulf of Maine. 3rd edition. Washington, DC: Smithsonian Institution Press, 2002.

McEachran, J. D., and J. D. Fechhelm. Fishes of the Gulf of Mexico. Vol. 1. Austin: University of Texas Press, 1998.

Nelson, Joseph S. Fishes of the World. 3rd edition. New York: John Wiley & Sons, 1994.

Paxton, J. R., and W. Eschmeyer, eds. Encyclopedia of Fishes. San Diego: Academic Press, 1995.

Pietsch, T. W., and D. B. Grobecker. Frogfishes of the World: Systematics, Zoogeography, and Behavioral Ecology. Stanford: Stanford University Press, 1987.

Robins, C. Richard, and G. Carleton Ray. A Field Guide to Atlantic Coast Fishes: North America. Boston: Houghton Mifflin Co., 1986.

Periodicals

Bigelow, H. B., and W. W. Welsh. "Fishes of the Gulf of Maine." Bulletin of the U. S. Bureau of Fisheries 40, no. 1(1925): 1–567.

Caruso, J. H. "The Systematics and Distribution of the Lophiid Anglerfishes. I. A Revision of the Genus Lophiodes with the Description of Two New Species." Copeia 1981, no. 3 (1981): 522–549.

——. "The Systematics and Distribution of the Lophiid Anglerfishes. II. Revisions of the Genera Lophiomus and Lophius." Copeia 1983, no. 1 (1983): 11–30.

——. "The Systematics and Distribution of the Lophiid Anglerfishes. III. Intergeneric Relationships." Copeia 1985, no. 4 (1985): 870–875.

Hoffman, H. A., and D. S. Jordan. "A Catalog of the Fishes of Greece, with Notes on the Names Now in Use and Those Employed by Classical Authors." Proceedings of the Academy of Natural Sciences of Philadelphia (1892): 230–285.

Pietsch, T. W., and D. B. Grobecker. "The Compleat Angler: Aggressive Mimicry in an Antennariid Anglerfish." Science 201, no. 4353 (1978): 369–370.

John H. Caruso, PhD