Beryciformes

(Roughies, flashlightfishes, and squirrelfishes)

Class Actinopterygii

Order Beryciformes

Number of families 7

Evolution and systematics

The order Beryciformes encompasses 7 marine families, 29 genera, and about 140 species. The seven families are:

• Anomalopidae, the flashlightfishes or lanterneye fishes
• Anoplogasteridae (also spelled Anoplogastridae), the fangtooth fishes
• Berycidae, the alfoncinos and redfishes
• Diretmidae, the spinyfins
• Holocentridae, the squirrelfishes and soldierfishes
• Monocentridae, the pineapplefishes or pineconefishes
• Trachichthyidae, the roughies or slimeheads

The order Beryciformes falls at the base of a large grouping of fishes collectively known as percomorphs. These advanced fishes include the order Perciformes, which comprises a great diversity of fishes including cichlids, perches, blennies, and barracudas. Like all other percomorphs, the beryciforms have a characteristic linked arrangement of the pelvic and pectoral girdles. They differ from other percomorphs in the number of rays in the tail fin. Caudal rays in most percomorphs number 17, but fishes in the Beryciformes order have 18 or 19. Systematists believe that as the fishes advanced evolutionarily, the number of tail-fin rays decreased. The fact that the Beryciformes have a greater number of caudal rays places them at the base of the percomorph lineage.

At one time, the order Beryciformes was larger and included the beardfishes, whalefishes, gibberfishes, and pricklefishes. Systematists once classified beardfishes as primitive beryciforms, but have now placed them in their own order, the Polymixiiformes, which precedes the evolution of the Beryciformes. The whalefishes, gibberfishes, and pricklefishes are in the order Stephanoberyciformes, and accompany the Beryciformes at the base of the percomorph lineage. The genera of beryciform fishes have also undergone some changes in classification. For example, the squirrelfishes have at one time or another been classified under the genera Adioryx, Flammeo, Holocentrus, Sargocentron, and Neoniphon, but the latter three are currently used.

The fossil record indicates that beryciform fishes occurred at least as far back as the late Cretaceous period, and were abundant. The group has persisted and is still quite common.

Physical characteristics

The Beryciformes are small- to medium-sized, spiny-rayed fishes, 3–24 in (8–61 cm) long. They have big eyes, some have colorful scales, and some have light organs beneath the eyes. The order is also defined partly by the number of softer, flexible rays in the ventral fin.

The Holocentridae is the largest family within the Beryciformes. Encompassing both the squirrelfishes and soldierfishes, fishes in this family are typified by a reddish color from head to tail and a noticeably forked tail. The trailing edges of their scales often have spines (called spinoid scales); some have spines on their gill covers.

Fishes in the family Anomalopidae, the flashlight or lantern-eye fishes, are distinguished primarily by the obvious light organ

under each eye. These fishes and the bioluminescent bacteria that generate the light have developed a symbiotic relationship that offers the bacteria a place to live, while giving the fishes illumination, perhaps for attracting zooplankton during night feeding and for intraspecific communication. Light organs are also seen in other beryciform fishes, including those in the family Monocentridae.

The monocentrids' whimsical common names of the pineapple and pineconefishes come from their beautiful, large scales. Usually yellow, each scale has its own dark outline, further accentuating an armorlike appearance. Like the holocentrids, species of the Monocentridae have spines poking backward from each scale.

Trachichthyids are known mostly from one species, the orange roughy (Hoplostethus atlanticus). This somewhat primitive-looking fish, as well as other members of this family, are distinguished by mucous cavities just beneath the skin of the head. This trait accounts for their less-than-flattering alternate common name of slimeheads.

Distribution

As a group, the beryciform fishes are found in tropical, subtropical, and temperate waters nearly around the globe. The holocentrids occur worldwide in tropical waters, although some venture further north or south. The alfoncinos and redfishes, spinyfins, and fangtooths prefer tropical to temperate waters worldwide. The pineapplefishes share this affinity, but remain in the Indian and Pacific Oceans. The flashlightfishes occur in the tropical seas from the western Atlantic to the Pacific; the roughy family favors the waters around Australia.

Habitat

Beryciform fishes cover a range of habitats. Some species, such as many of the squirrelfishes, gravitate toward shallow, tropical reefs. Others, such as the roughies, spend their lives in deep, dark, ocean waters. Most roughies inhabit continental-shelf and slope waters almost 5,280 ft (1,609 m) deep. Certain spinyfins and fangtooth species share this preference for deep waters, and live along the sea bottom 6,600 ft (2,012 m) down.

Beryciforms that live in shallow waters shun the light, usually tucking themselves under a coral overhang, backing into a cave, or hiding below another structure during the day. During daytime excursions, divers frequently encounter squirrelfishes poking out from some type of dark sanctuary. Shallow-dwelling species sometimes maintain a daily routine of descending into deep waters and remaining mostly inactive during the day, then rising into the shallows at night to feed. A few, such as the flashlightfishes, further avoid the light by limiting their shallow-water forays to nights of a new moon, or to the periods before the moon rises and after it sets.

Behavior

Perhaps the most notable characteristic of the beryciform fishes is their ability to produce light, and in some cases, readily control it. The light is the result of bioluminescent bacteria that take up residence in pockets just below the skin of various species, including the flashlight, pineapple, and pineconefishes. Other beryciform fishes also have light organs, including members in the genera Sorosichthys and Paratrachichthys. As well as using the light to find and/or to attract

prey during their nocturnal feeding forays, in some cases these fishes apparently employ the illumination as a means of communication between members of the their own species and as a method of confusing potential predators. This assumption is based on observations of alterations in the blinking pattern of the light when conspecifics approach one another or when a predator swims nearby. The eyelight fish (Photoblepharon palpebratus) can control its light production by lifting or dropping a flap of skin over the light organ. Other species have other ways of controlling the light.

Several beryciform species also make noises, either when interacting with members of their own species or with other fishes. The squirrelfishes are noted for their grunting and clicking sounds, which they produce with the swim bladder.

Feeding ecology and diet

Beryciformes feed on small fishes and various invertebrates. The shallow-dwellers are primarily nocturnal feeders, although some will feed on invertebrates passing through their diurnal retreats. For example, squirrelfishes primarily dine on the small fishes, various crabs, shrimps, and other crustaceans and zooplankton they find in the reef at night, but will take an invertebrate during the day if one happens to wander nearby.

Fishes in this order are known by their large eyes, which allow them to see in low-light conditions. Some have the added advantage of light organs, which assist in finding and perhaps attracting prey. Species in the Monocentridae and Anomalopidae use their light organs to fill their diet of crustaceans. The Australian pineapplefish (Cleidopus gloriamaris) has light organs near the mouth and uses them like bluish spotlights at night when it ventures out from its cave hideout to find food. The similar-appearing pineconefish (Monocentris japonica) is believed to use its light organs to lure light-responsive prey after it has seen them rather than to find them in the first place.

Predators for these fishes may include sea birds for shallow-dwelling species, as well as many of the larger, piscivorous fishes of their habitat.

Reproductive biology

Little is known about the reproductive biology of the Beryciformes. No observations or studies have shown hermaphroditism

or sex reversal among the species; they are born male or female and remain that way throughout their lives. Scientists believe that all beryciform fishes have external fertilization.

More is known about the reproduction in squirrelfishes, because these fishes are common in reefs where they are frequently observed by divers. During mating in the Hawaiian squirrelfish (Sargocentron xantherythrum), a male and female grunt and click, align themselves side by side, and place their tails together while fanning out their heads to the left and right.

The mating of the red soldierfish (Myripristis murdjan) in the Holocentridae, has also been observed. The male and female courtship ritual involves an inward-spiraling swimming pattern between the two, followed by a quick, adjacent rise through the water when both eggs and sperm are ejected for fertilization.

Conservation status

No species of Beryciformes is listed by the IUCN.

Significance to humans

Various members of the Beryciformes are important in the pet trade. The colors of the pineapplefishes and squirrelfishes and the glowing organ of the flashlightfishes all draw interest from aquarium keepers. Divers also appreciate the reds of the shallow-dwelling squirrelfishes, even if they are mostly viewed in dark crevices and other hiding spots during the day. Several beryciforms, including the orange roughy, are commercially harvested as food.

Species accounts

List of Species

Splitfin flashlightfish

Anomalops katoptron

family

Anomalopidae

taxonomy

Anomalops katoptron Bleeker, 1856, Manado, Sulawesi [Celebes], Indonesia.

other common names

English: Flashlightfish, great flashlightfish, Indian flashlightfish, lanterneye fish; twofin flashlightfish; German: Lanternenfisch.

physical characteristics

Reaches length of nearly 12 in (about 30 cm). The smaller splitfins average about 4 in (10.2 cm) and live in shallower areas. Color brownish black. Has the typical large eye of the beryciforms. They have two dorsal fins; the hindmost fin is triangular and much larger than the front dorsal fin. Two light organs are noticeable just beneath each eye.

distribution

Western South Pacific, from Malaysia east to the Tuamotu Archipelago, and from the Great Barrier Reef up to southern Japan.

habitat

Prefers deeper reef areas of 650–1,300 ft (200–400 m), but is also seen in depths as shallow as 65 ft (20 m). During the day, it remains hidden from sunlight, either in deep water or in dark caves. In winter months, the species aggregates in the warmer, shallower waters of the Philippines.

behavior

Fishes in this species have a light-producing organ, and regulate it using a muscular attachment that rotates the gland, either to allow the bioluminescent bacteria to shine forth or to hide the glow from view. The fishes can control the light, which they use to communicate with conspecifics. Splitfin flashlightfishes often travel in schools of 24 to 48 fish.

feeding ecology and diet

Uses its large light organ during feeding, which is primarily a nocturnal activity. These fishes shun even dim external light, opting to search for food before or after the moon has risen and set, or on nights of a new moon. Their diet is mainly zoo-plankton.

reproductive biology

Little is known about the reproductive biology of the splitfin flashlightfish, but they probably do not guard eggs.

conservation status

Not listed by the IUCN.

significance to humans

Part of the aquarium trade; sometimes used as bait fish.

Common fangtooth

Anoplogaster cornuta

family

Anoplogasteridae

taxonomy

Anoplogaster cornuta Valenciennes, 1833, S. Atlantic.

other common names

English: Common sabertooth, ogrefish; Spanish: Pez con colmillos.

physical characteristics

Can reach up to 6 in (15.2 cm) in length. Their huge head, large mouth opening, and long, sharp teeth combine to give these fishes a rather frightening appearance. With long spines on their heads, the light-gray juveniles look quite different from adults, and were identified as a separate species for many years.

distribution

Temperate to tropical waters around the world.

habitat

Prefers deeper waters of 1,650–6,600 ft (500–2,000 m), but some occur as far down as 16,100 ft (4,900 m). Juveniles will venture almost to the surface.

behavior

Fangtooths live singly or in small groups.

feeding ecology and diet

Adult fangtooths are mainly piscivores, feeding by opening their large mouth to draw in prey. The young primarily subsist on crustaceans.

reproductive biology

Engages in external fertilization, and provides no parental care to eggs or young. The larvae are planktonic.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Squirrelfish

Holocentrus ascensionis

family

Holocentridae

taxonomy

Holocentrus ascensionis Osbeck, 1765, Acension Island.

other common names

English: Common squirrelfish, longjaw squirrelfish, French: Marignan coq; Spanish: Candil gallito.

physical characteristics

A reddish, sometimes blotched, fish with a large dark eye. Typically grows to about 12 in (30.5 cm), although reports exist of specimens twice that size. Has a double dorsal fin, with the front fin comprising sharp spines and taking a yellowish hue. The back fin is much taller, with flexible rays.

distribution

Gulf of Mexico and the western Atlantic Ocean from New York to Brazil, and east to Bermuda. Eastern Atlantic in

Gabon, Angola, St. Paul's Rocks, St. Helena, and Ascensión Island.

habitat

Subtropical reefs with suitable structures for hiding during the day. Commonly seen by divers in very shallow waters, but also found at depths down to 590 ft (180 m).

behavior

Remains hidden from view during the day, either in deeper waters or in shallow-water crevices. May occur alone or in aggregations of up to a few dozen fish. This species makes grunting and clicking noises.

feeding ecology and diet

Mainly nocturnal feeders, consuming crustaceans and other invertebrates. Predators include sea birds and other fishes, such as the common dolphinfish (Corphaena hippurus), mutton snapper (Lutjanus analis), and yellowfin tuna (Thunnus albacares).

reproductive biology

Mating behavior includes a pairing of male and female, during which they bring their tails together while their heads face away from one another. The eggs are pelagic. The larvae often venture far out to sea, and return to the reefs as adults.

conservation status

Not listed by the IUCN.

significance to humans

Enjoyed by divers in their natural habitat, squirrelfishes are also part of the aquarium trade.

Blackbar soldierfish

Myripristis jacobus

family

Holocentridae

taxonomy

Myripristis jacobus Cuvier, 1829, Martinique Island, West Indies; Brazil; Havana, Cuba.

other common names

English: Bastard soldierfish, roundhead conga; French: Marignon mombin; Spanish: Candil de piedra.

physical characteristics

Grow up to 10 in (25 cm) in length. Somewhat similar in appearance to the squirrelfish, they are red with a large eye, double dorsal fin, and forked tail, but also sport a brownish black, vertical bar behind the gillcover that extends to the pectoral fin.

distribution

Gulf of Mexico and the eastern Atlantic, north to North Carolina and south to Brazil.

habitat

Reefs and other structures, including piers. Commonly seen by divers in very shallow waters, but also found at depths to 330 ft (100 m).

behavior

Usually a solitary species, but small groups of up to 36 individuals sometimes school. Under stress, blackbar soldierfishes will make clicking and grunting noises with the swim bladder.

Divers have seen an occasional blackbar soldierfish swimming upside down, and they commonly swim upside down in caves.

feeding ecology and diet

Nocturnal feeder. Eats shrimp and zooplankton. Predators include such fishes as the horse-eye jack (Caranx latus), West Atlantic trumpetfish (Aulostomus maculatus), and Nassau grouper (Epinephelus striatus).

reproductive biology

Engage in external fertilization on days following a full moon. While the adults prefer shallower reefs, the larvae may travel well out to sea.

conservation status

Not listed by the IUCN.

significance to humans

Major part of the pet trade and a minor commercial food fish.

Pineconefish

Monocentris japonica

family

Monocentridae

taxonomy

Monocentris japonica Houttuyn, 1782, Nagasaki, Japan.

other common names

English: Dick bridegroom fish, Japanese pineapplefish, knight fish, pine sculpin; French: Poisson ananas; German: Japanischer Reuterfisch/Tannenzapfenfisch.

physical characteristics

Can reach 6.5 in (16.5 cm) in length. Has large scales bordered in black. The scales are armed with spines that point toward the tail. The light organ is located near the mouth.

distribution

Southern Japan, spreading down to southern Australia, and west to the Red Sea.

habitat

Prefers rocky reefs. The young are found in shallow waters of 10–20 ft (3 to 6.1 m); the adults inhabit depths of 60–700 ft (18–213 m).

behavior

Usually solitary or in pairs, but individuals sometimes congregate in schools of 50–100.

feeding ecology and diet

Nocturnal feeder. Searches sandy sea bottoms for prey, which includes small fishes, shrimps, and other invertebrates.

reproductive biology

Mostly unknown, but they probably do not guard the eggs or young.

conservation status

Not listed by the IUCN.

significance to humans

Pineconefishes are a minor part of the aquarium trade.

Orange roughy

Hoplostethus atlanticus

family

Trachichthyidae

taxonomy

Hoplostethus atlanticus Collett, 1889, Florés, Azores, sta. 203, 1557 m.

other common names

English: Deep sea perch, red roughy, slimehead; French: Hoplostète orange; German: Degenfisch, Granatbarsch, Kaiserbarsch; Spanish: Raloj anaranjado

physical characteristics

Among the largest of the beryciform fishes, and possibly the largest, with some specimens up to 29.5 in (75 cm) in length. Has vivid orange-red coloration and a slightly jutting lower jaw.

distribution

Disjunct populations in tropical, subtropical, and temperate waters worldwide.

habitat

Prefers deep waters 590–5,900 ft (180–1,800 m) deep over steep or rough structures, particularly seamounts.

behavior

Apparently sedentary rather than migratory. Remains in deep waters most of its life. Little is known about the young, but they are believed to primarily inhabit deep waters, too.

feeding ecology and diet

Diet is made up of small fishes, shrimps, squids, and other invertebrates. Predators include other fishes of their habitat, such as basketwork eels (Diastobranchus spp.).

reproductive biology

Large groups of orange roughies congregate in annual mating schools. The schools may last one to two weeks, during which mature adults (30 years old and more) spawn and then leave the area. Females produce 10,000–90,000 eggs, which are fairly large at 0.08 in (2 mm) and spherical. The eggs drift toward the surface, where they hatch about two weeks later.

conservation status

Although the orange roughy is not listed by the IUCN, catches have been restricted to help ensure a continued commercial harvest.

significance to humans

Best known as a commercial food fish, providing millions of pounds of harvest each year. Commercial harvests are now restricted, but past annual harvests have topped 100 million pounds (45 million kg) in the waters off Australia and New Zealand.

Resources

Books

Deloach, Ned. Reef Fish Behavior. Jacksonville, FL: New World Publications, 1999.

Helfman, Gene S., Bruce B. Collette, and Douglas E. Facey. The Diversity of Fishes. Malden, MA.: Blackwell Science, 1997.

Michael, Scott W. "Family Anomalopidae: Flashlightfishes; Family Monocentridae: Pineapple Fishes; Subfamily Holocentrinae: Squirrelfishes; and Subfamily Myripristinae: Soldierfishes." In Reef Fishes: A Guide to Their Identification, Behavior and Captive Care, Vol. 1. Shelburne, VT: Microcosm Ltd., 1998.

Nelson, Joseph S. Fishes of the World. New York: John Wiley Sons, Inc., 1994.

Paxton, John R. "Squirrelfishes and Their Allies." In Encyclopedia of Fishes. 2nd edition, edited by John R. Paxton and William N. Eschmeyer. San Diego: Academic Press, 1998.

Snyderman, Marty, and Clay Wiseman. Guide to Marine Life: Caribbean, Bahamas, Florida. New York: Aqua Quest Publications, 1996.

Periodicals

Gauldie, R. W., and J. B. Jones. "Stocks, or Geographically Separated Populations of the New Zealand Orange Roughy, Hoplostethus atlanticus, in Relation to Parasite Infestation, Growth Rate, and Otolith Shape." Bulletin of Marine Science 67, no. 3 (2000): 949–972.

Leslie Ann Mertz, PhD