Blennies

Class Actinopterygii Order Perciformes Suborder Blennioidei Number of families 6

Photo: A mimic blenny (Aspidontus taeniatus) peers out from a wormhole in coral near the Florida Islands, Solomon Islands. (Photo by Fred Mc-Connaughey/Photo Researchers, Inc. Reproduced by permission.)

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 de-scendents, 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, Chaenopsi-dae, Clinidae, Dactyloscopidae, Labrisomidae, and Triptery-giidae) 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

A barnacle blenny (Acanthemblemaria sp.) from the eastern Pacific near Costa Rica. (Photo by Mark Smith/Photo Researchers, Inc. Reproduced by permission.)

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 rock-hopper 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. Saber-toothed blennies display previously known types of mimicry, as well as several newly discovered mimetic associations. Bate-sian mimicry (the most common form) involves a palatable species adapting to resemble an unpalatable species. Muller-ian 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 feed-

A large-banded blenny (Ophioblennius steindachneri) between two pencil urchins near Caldwell Rock, Galápagos Islands. (Photo by Fred Mc-Connaughey/Photo Researchers, Inc. Reproduced by permission.)
A jeweled blenny (Salarias fasciatus) living in an old coconut shell. (Photo by David Hall/Photo Researchers. Reproduced by permission.)

ing 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; Protemblemariapunctata (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.

1. Blackcheek blenny (Starksia lepicoelia); 2. Rosy weedfish (Heteroclinus roseus); 3. White-lined comb-tooth blenny (Ecsenius pictus); 4. Secretary blenny (Acanthemblemaria maria); 5. Sand stargazer (Dactyloscopus tridigitatus); 6. Striped poison-fang blenny (Meiacanthus grammistes); 7. Hairtail blenny (Xiphasia setifer); 8. Miracle triplefin (Enneapterygius mirabilis). (Illustration by Patricia Ferrer)

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