Blennioidei

(Blennies)

Class Actinopterygii

Order Perciformes

Suborder Blennioidei

Number of families 6

Evolution and systematics

The suborder Blennioidei has a long and convoluted history of classification, with a variety of families historically being moved into and out of the suborder. Stability finally was established for the suborder when Springer defined the Blennioidei as a monophyletic suborder (i.e., a taxon that includes all the evolutionary descendents, and only those descendents, of a common ancestor). Although the composition of the suborder has been established, the phylogenetic relationships to other families within the order Perciformes remain elusive.

The members of the six families (Blenniidae, Chaenopsidae, Clinidae, Dactyloscopidae, Labrisomidae, and Tripterygiidae) included in the Blennioidei uniquely share a distinctive shape of the joined pelvic bones; another important character is the absence of the second infrapharyngobranchial bone (PB2) from the dorsal gill arch. Springer documented the absence of the PB2 and described the shape of the joined pelvic bones as "a somewhat bean- or nut-like pod, which is open ventrally, and has a dorsally extending flange anteriorly on each side." In addition to this unusual pelvic shape and the loss of the PB2, several other characters that are rarely found in non-blennioid taxa define the Blennioidei. For example, there are cirri on the eye and often on the nape (absent in Dactyloscopidae), the bases of the pelvic fins are positioned anterior to the bases of the pectoral fins, several hypural bones supporting the caudal fin are fused, the anal fin has fewer than three spines, and all segmented rays are unbranched. Johnson described another character, the lack of a neural spine on the first vertebra, further corroborating that the Blennioidei make up a monophyletic group. Although one or a few of these individual characters occur variously in other families, the combination of more than a few of the many shared specialized characters is not found in non-blennioid families.

Few blennioid fossils have been discovered. The combination of their small size and a predominant occurrence along coastlines exposed to wave action and surge probably contributed to the rarity of blenny fossils. The oldest reported blennioid fossil is a late Eocene blennioid otolith described by Nolf.

As of 2002, there are 127 genera and about 750 recognized species in the Blennioidei. Being small, cryptic fishes, blennioids are frequently difficult to collect and identify. The use of rotenone (a natural plant substance found in the roots of a variety of leguminous plants, which aids in the collection of cryptic fishes) to conduct scientific biodiversity surveys of fishes is resulting in the continuous discovery of previously unknown new species of blennioids. If discoveries of new blennioid taxa continue at the current pace, there ultimately may be 1,000 or more valid species of blennioids.

Physical characteristics

Blennioids exhibit amazing diversity in body shapes. They are typically small fishes, usually less than 4 in (15 cm) in length, with many species growing no longer than 2 in (5 cm). Their slender, elongate bodies are very flexible. Most blennioids (not dactyloscopids) have cirri on the head, particularly over the eyes and often on the nape. The only members of the suborder attaining lengths of more than about 10 in (25 cm) are specimens belonging to one Indo-Pacific genus, Xiphasia, which have extremely elongate bodies with a depth of less than 0.8 in (2 cm) but reaching lengths of 21.3 in (54 cm). Body shapes range from short and stout and completely or almost completely scaled to elongate and blunt-headed and entirely lacking scales. Several species in the tube blenny genus Acanthemblemaria have enlarged spines adorning their heads. Some of the sand stargazers have flattened heads with eyes

set on protruding stalks. These fish burrow into the sand with only the stalked eyes sticking out as they lie in wait for unsuspecting prey.

Color patterns vary widely, ranging from drab, camouflaging mottled patterns of brown and tan to brilliant reds, yellows, and iridescent blues. Males and females of many blennioid taxa have extremely different colors and patterns. Historically, these differences sometimes have resulted in males and females of the same species being described as two different species.

Distribution

Blennioids are found in shallow marine, estuarine waters of every continent but rarely in freshwaters. The highest diversity of blennioids is in shallow tropical and temperate waters of the Caribbean, western Atlantic, Indian, and Pacific Oceans. Blennioids have not been found in the Arctic Ocean, but they are present in the shallow coastal waters of every other ocean. There is even one triplefin species known from the coast of Antarctica.

Habitat

Blennioids reside in almost every underwater marine habitat imaginable, and some even climb out of the water onto rocks. They are predominately benthic (a few are secondarily free-swimming) and found on or near coral and rocky reefs, where they live in holes and crevices. Other blennioids may live on the bottom among mangrove roots, in sea grass beds, on oyster reefs, or in sandy areas. Although most species live at depths shallower than 66 ft (20 m) and typically less than 33 ft (10 m), Bathyblennius antholops is known only from a specimen taken at a depth between 330 and 420 ft (101–128 m). The freshwater blenny, Salaria fluviatilis, of northern Africa and southern Europe is one of the few blennioids that lives in freshwater streams and rivers. (Some Omobranchini and Phenablennius live in freshwater habitats as well.)

Behavior

Blennioids usually are seen in shallow water, sitting on rocks or coral rubble and using their pelvic fins as props to lift the head off the bottom. They quickly dart into a hole or crevice when approached by a diver. The Indo-Pacific rockhopper blennies of the genera Alticus and Andamia are found on rocks in high-energy surf zones. The rockhoppers sit just above the waterline and, when threatened, leap from the rock and use quick flicks of the anal and tail fins to skip across the surface of the water to the next emergent rock.

Mimetic associations have been documented for many of the saber-toothed blennies. Mimicry is the process of one species or specimen gaining survival value by changing superficially to resemble another species or specimen. Sabertoothed blennies display previously known types of mimicry, as well as several newly discovered mimetic associations. Batesian mimicry (the most common form) involves a palatable species adapting to resemble an unpalatable species. Müllerian mimicry is defined as two unpalatable species resembling each other. When a predatory and aggressive species resembles a nonagressive species, this is referred to as aggressive mimicry. Social mimicry is seen when two or more species with a similar color pattern swim together in a group for mutual protection.

Feeding ecology and diet

Most blennioids are predatory, eating small benthic invertebrates. The members of the family Blenniidae exhibit a broad range of feeding habits. Some blennies have a row of flexible, comblike teeth used to scrape algae and any associated organisms in the algal mat. Other blennies range in feeding

habits from fin ray–eating and membrane-eating aggressive mimics to tube-dwelling plankton pickers. Blennioids are also subject to predation; while the exact predators have not been identified, blennioids are probably eaten by groupers, snappers, and other large piscivores.

Reproductive biology

Reproductive biology is unknown for all but a few blennioids. In the family Blenniidae, males of some species guard and display in front of a small territory, often an empty shell or a rock crevice. The female enters the male's territory; lays large, demersal eggs that adhere to the surface of the shell or rock as they are fertilized by the male; and then leaves. The female sometimes visits two or more males in sequence, repeating the spawning process with each one. The male then guards the eggs and fans water over them until they hatch. Newly hatched fry swim toward the surface and feed on plankton until they settle. The duration of the larval stage varies widely—some blennies settle within a few days of hatching, whereas others may have an extended pelagic larval stage, called the ophioblennius stage, lasting up to one or two months.

The South African, Australian, and Mediterranean members of the Clinidae are ovoviviparous, but the South American members of the family lack an intromittent organ and are oviparous. The tropical eastern Pacific labrisomid genus Xenomedea is also ovoviviparous. Males of the labrisomid genus Starksia have a distinctive tubular intromittent organ, but live embryos have been found only in a few eastern Pacific Starksia species and have not been recorded for any of the Atlantic species.

Conservation status

As of 2002 most populations of marine blennioids were stable, but increasing destruction of coral reefs and coastal pollution are potential threats. The greatest conservation threat to blennioids comes from habitat destruction and pollution. Four species in three families appear on the IUCN Red List—Entomacrodus cadenati (Blenniidae) listed as Data Deficient; Coralliozetus tayrona (Chaenopsidae) listed as Vulnerable; Protemblemaria punctata (Chaenopsidae) listed as Vulnerable; and Clinus spatulatus (Clinidae) listed as Endangered. There are no conservation or preservation efforts underway.

Significance to humans

Although blennioids are eaten and can be seen regularly in fish markets from the Philippines to Indonesia and in Peru and Chile in the eastern Pacific, they are not considered commercially important. The primary use of blennioids by humans is as aquarium fish. Specimens of the eastern Pacific blenniid genus Scartichthys are consumed in Peru, where eating the flesh supposedly produces a drunken effect. The common name for these fish in Peru is borracho, which means "drunk." On Easter Island the Rapa Nui people consider the small patuki blenny to have transformational qualities and associate it with fertility.

Species accounts

List of Species

Hairtail blenny

Xiphasia setifer

family

Blenniidae

taxonomy

Xiphasia setifer Swainson, 1839, Vizagapatam, Philippines.

other common names

Japanese: Unagiginpo; South Africa: Slangblennie; Oman and Micronesia: Snakeblenny.

physical characteristics

May reach lengths of 23.6 in (60 cm). Large fangs in each jaw but not associated with a toxin gland. Body with alternating bands of dark brown and pale brown. Caudal fin with middle two rays very elongate and forming a hairlike filament and dorsal fin originating above the eye and continuing to the caudal fin. Extremely long and slender body.

distribution

Widely distributed from the western Indian Ocean to the western central Pacific.

habitat

Usually found in tubes or burrows in mud or sandy bottoms but may be seen swimming above the bottom or at the surface at night while feeding; shelters in tubes or burrows during the day. Specimens have been captured by trawl at 164–177 ft (50–54 m) off western India.

behavior

Seldom seen underwater but sometimes attracted to night lights, probably in search of small invertebrates to eat.

feeding ecology and diet

Appears to be nocturnal and to forage on small invertebrates.

reproductive biology

Not known.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Striped poison-fang blenny

Meiacanthus grammistes

family

Blenniidae

taxonomy

Meiacanthus grammistes Valenciennes in Cuvier and Valenciennes, 1836, Java, Indonesia.

other common names

English: Grammistes blenny; Japanese: Hige-nijiginpo.

physical characteristics

May reach lengths of 3.5 in (90 mm). Has a toxin-producing gland enclosed in the dentary at the base of each enlarged, grooved lower-jaw fang. Body has alternating black and white stripes. White stripes are yellowish anteriorly; black stripes are narrow as they approach the base of the caudal fin, where

they break up into small black spots. Caudal fin is translucent, with small black spots; dorsal and anal fins have a black sub-marginal stripe.

distribution

Widely distributed throughout the western central Pacific from the Ryukyu Islands in the north to the Great Barrier Reef in the south and eastward to the Solomon Islands.

habitat

Usually found on or near coral reefs and may be seen swimming above the reef; shelters in tubes or holes in the reef.

behavior

This is a venomous species that is able to inject venom using modified fangs in the lower jaw. Unlike most blennies, these fishes have a well-developed swim bladder that allows them to swim easily above the reef. The combination of the swim bladder and their ability to inject venom into a potential predator allows them to swim without restriction above the reef and to forage over a relatively wide area. Like most species of Meiacanthus, the striped poison-fang blenny has mimics. Two species are known to be Batesian mimics, a blenniid (Petroscirtes breviceps) and a cardinalfish (Cheilodipterus nigrotaeniatus). Both of these species swim with the striped poison-fang blenny and avoid predation as a result of potential predators' aversion to the bite of the striped poison-fang blenny.

feeding ecology and diet

Forages on small benthic invertebrates on or near the reef.

reproductive biology

Unknown but probably similar to that of other blennies. Among other blennies, the male displays to entice one or more females to lay demersal eggs in a hole in the reef, and the male probably guards the eggs until they hatch.

conservation status

Not listed by the IUCN.

significance to humans

Sold as aquarium fish. Potential medicinal uses for substances produced by the venom glands have not been explored.

White-lined comb-tooth blenny

Ecsenius pictus

family

Blenniidae

taxonomy

Ecsenius pictus McKinney and Springer, 1976, Molucca Islands, Indonesia.

other common names

Micronesia: Pictus blenny.

physical characteristics

May reach lengths of 2 in (50 mm). Has anterior and posterior canines on each side of the lower jaw and lacks orbital and nape cirri. Body is brown with a series of narrow white stripes ending at the caudal peduncle. The caudal peduncle is yellowish with several brown bands.

distribution

Known to occur only in the western central Pacific in the Philippines, Indonesia, and the Solomon Islands.

habitat

Usually found on or near coral reefs at depths of 36–131 ft (11–40 m).

behavior

A benthic fish, generally seen perched on coral.

feeding ecology and diet

Forages on small benthic invertebrates on or near the reef.

reproductive biology

Not known.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Secretary blenny

Acanthemblemaria maria

family

Chaenopsidae

taxonomy

Acanthemblemaria maria Böhlke, 1961, Treasure Island, Bahamas.

other common names

None known.

physical characteristics

May reach lengths of 2 in (50 mm). Head has well-developed bony spines covering the top almost to the dorsal

fin origin. Body has broad brown bands separated by narrow pale areas; dark bands sometimes form large oval spots midlaterally.

distribution

Bahamas eastward to Belize and southward to Tobago.

habitat

Inhabits small tubes or holes abandoned by tube worms or other invertebrates in rock or limestone slopes and usually is found at depths shallower than 33 ft (10 m).

behavior

Generally seen with only the head projecting from a hole, retreating into the hole on the approach of a diver or a large fish.

feeding ecology and diet

Feeds on small benthic invertebrates.

reproductive biology

Oviparous. Spawning has not been observed but is probably similar to that of other egg-laying blennies.

conservation status

Not listed by the IUCN. Healthy numbers exist in the western Atlantic and Caribbean. Local populations could be threatened by habitat destruction or pollution.

significance to humans

Potential significance as aquarium fish.

Rosy weedfish

Heteroclinus roseus

family

Clinidae

taxonomy

Heteroclinus roseus Günther, 1861, Freycinets Harbour, Western Australia.

other common names

Japanese: Beni-asahiginpo.

physical characteristics

May reach maximum lengths of 5.7 in (145 mm). The rosy weedfish is distinguished from other Heteroclinus species by having a black spot, bordered above and below by a white stripe, on the pectoral fin-base.

distribution

Primarily anti-subtropical in distribution, occurring north of approximately 20° N latitude and south of roughly 20° S latitude, and absent in tropical equatorial waters. A northern population occurs in Japan and a disjunct southern population living around the southern half of Australia, Lord Howe Island, Kermadec Islands, New Caledonia, and Vanuatu.

habitat

The rosy weedfish lives on rocky reefs from the intertidal zone to depths of 115 ft (35 m).

behavior

Rarely seen underwater owing to its very cryptic coloration. Sits on the bottom using its pelvic fins as supports to lift the head.

feeding ecology and diet

Predatory, probably feeding on small benthic invertebrates.

reproductive biology

The presence of an intromittent organ in males suggests that it (like all other clinids in the Indo-Pacific) is ovoviviparous.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Sand stargazer

Dactyloscopus tridigitatus

family

Dactyloscopidae

taxonomy

Dactyloscopus tridigitatus Gill, 1859, Barbados.

other common names

Spanish: Mirón ojilargo.

physical characteristics

May reach lengths of 3 in (75 mm). A distinctive Atlantic sand stargazer with the eye perched on a slender stalk on top of the head. It differs from other Atlantic sand stargazers in that it has a tube in the last lateral line scale at the base of the caudal fin.

distribution

Bermuda, northeastern Gulf of Mexico, Bahamas, and the Caribbean as far as Brazil.

habitat

Soft, sandy bottoms from shallow water off beaches to depths of 98 ft (30 m).

behavior

Burrows into the sand with only the stalked eyes on the top of the head exposed.

feeding ecology and diet

It is predatory on small prey, presumably invertebrates, but the sand stargazer has not been observed feeding.

reproductive biology

Oviparous. Males and females mature at about 1.8 in (45 mm) in length. Spawning had not been observed as of 2002.

conservation status

Not listed by the IUCN. Pollution is the biggest potential threat.

significance to humans

None known.

Blackcheek blenny

Starksia lepicoelia

family

Labrisomidae

taxonomy

Starksia lepicoelia Böhlke and Springer, 1961, Green Cay, Bahamas.

other common names

Spanish: Sapito carinegro.

physical characteristics

May reach a maximum length of 1.4 in (35 mm). The blackcheek blenny can be distinguished from other Atlantic Starksia by the presence of a black spot covering most of the cheek in mature males, a completely scaled belly, and male genital papilla entirely separate from the first anal fin spine.

distribution

May be found on coral reefs from the Bahamas and throughout the Caribbean.

habitat

Coral reefs at depths of 26–66 ft (8–20 m).

behavior

Secretive and rarely seen underwater.

feeding ecology and diet

Predatory on small benthic invertebrates.

reproductive biology

Mature females have well-developed ova in the ovaries, and the males have an intromittent organ, but the presence of embryos in a female (viviparity) has not been documented. It seems likely that the species is oviparous, as no gravid female Atlantic blackcheek blenny has ever been found.

conservation status

Not listed by the IUCN.

significance to humans

None known.

Miracle triplefin

Enneapterygius mirabilis

family

Tripterygiidae

taxonomy

Enneapterygius mirabilis Fricke, 1994, Escape Reef, Australia.

other common names

None known.

physical characteristics

May reach lengths of 1.2 in (30 mm). Distinguished from other Enneapterygius species by having 12 or fewer tubed scales in the anterior portion of the lateral line and by its long, filamentous spines in the first dorsal fin.

distribution

Known from Papua New Guinea, northern Queensland, Australia, and Vanuatu.

habitat

Has been found at depths of 26–121 ft (8–37 m) on coral reefs and adjacent reef slopes.

behavior

The miracle triplefin, like so many of the blennioids, has yet to be observed alive underwater. It has been seen and collected only after the application of rotenone, without which this magnificent blenny's existence would be unknown.

feeding ecology and diet

The diet is unknown, but the presence of small, sharp, conical teeth in the jaws suggests that the miracle triplefin feeds on small benthic invertebrates.

reproductive biology

Oviparous, based on the presence of mature ova in females, but breeding individuals have not been observed, and young are unknown.

conservation status

Not listed by the IUCN.

significance to humans

Not currently used by humans, but its red color and high first dorsal fin make it an attractive species.

Resources

Books

Gomon, M. F., J. C. M. Glover, and R. H. Kuiter. The Fishes of Australia's South Coast. Adelaide, Australia: State Print, 1994.

Periodicals

Johnson, G. D. "Percomorph Phylogeny: Progress and Problems." Bulletin of Marine Science 52, no. 1 (1993): 3–28.

Nolf, D. "Les Otolithes de Teleosteens Eocenes d'Aquitaine (Sud-Ouest de la France) et Leur Interet Stratigraphique." Academie Royale de Belgique, Memoires de la Classe des Sciences 19, no. 2 (1988): 7–147.

Smith, C. L., J. C. Tyler, H. Andreyko, and D. M. Tyler. "Behavioral Ecology of the Sailfin Blenny, Emblemariopsis pandionis (Pisces: Chaenopsidae) in the Caribbean off Belize." American Museum Novitates 3232 (1998): 1–40.

Smith-Vaniz, William F., Ukkrit Satapoomin, and Gerald R. Allen. "Meiacanthus urostigma, a New Fangblenny from the Northeastern Indian Ocean, with Discussion and Examples of Mimicry in Species of Meiacanthus (Teleostei: Blenniidae: Nemophini)." Aqua, Journal of Ichthyology and Aquatic Biology 5, no. 1 (2001): 25–43.

Springer, V. G. "Definition of the Suborder Blennioidei and Its Included Families (Pisces: Perciformes)." Bulletin of Marine Sciences 52, no. 1 (1993): 472–495.

——. "The Indo-Pacific Blenniid Fish Genus Ecsenius." Smithsonian Contributions to Zoology, no. 465 (1988): 1–134.

Jeffrey Taylor Williams, PhD