TripterygiidaeThreefin blennies

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Diversity

Tripterygiids (triplefin blennies) are one of the least-studied blennies, but they are known to be cryptic, territorial reef dwellers identifiable by their three distinct dorsal fins and ctenoid (rough-edged) scales. There are some undescribed forms among the Tripterygiidae, but there are thought to be at least 20 genera and 150 species in the family. (Allen and Robertson, 1994; Böhlke and Chaplin, 1994; Helfman, et al., 1997; Nelson, 1994; Springer, 1998; Thresher, 1984; Wheeler, 1985)

Geographic Range

Triplefin blennies are found in the Atlantic, Pacific, and Indian Oceans, and one species has been identified in the Antarctic Peninsula. There are five species known to be from the Bahamas, all of which are located in the Bahamas. Blennies are generally not found on most of the Atlantic coasts of Africa and South America. New Zealand is thought to be the area with greatest diversity of triplefin blennies. (Böhlke and Chaplin, 1994; Nelson, 1994; Springer, 1998)

Habitat

Primarily benthic reef-dwellers in tropical and warm temperate seas, triplefin blennies commonly live near reef surfaces, rocky slopes, rubble, or algae-covered rocks. Depth and habitat can vary according to specific local adaptations. One species can sometimes be found in estuaries. (Allen and Robertson, 1994; Böhlke and Chaplin, 1994; Graham, 1997; Nelson, 1994; Springer, 1998; Thresher, 1984; Wheeler, 1985)

Physical Description

Triplefin blennies are cryptically colored or transparent, heavily scaled, and small. Most are only 3-4 cm, the largest reaching 25 cm. In triplefin blennies the dorsal fin is divided into three distinct parts. The first two segments are composed of numerous slender spines, and the third segment is made up of at least seven soft rays. There are between zero and two anal fin spines. Scales are usually, but not universally, ctenoid (rough-edged or toothed). The nape lacks cirri, and the first gill arch attaches to the operculum, the latter characteristic distinguishing Tripterygiidae from Clinidae. Sexual dimorphism is common, with males assuming black or red coloration on the head, body, or caudal fin during spawning. Urogenital (involving both the urinary and genital structures) morphology may also differ between males and females. Gray and brown are typical colors on females and nonspawning males. (Click here to see a fish diagram). (Allen and Robertson, 1994; Böhlke and Chaplin, 1994; Nelson, 1994; Springer, 1998; Thresher, 1984; Wheeler, 1985)

  • Sexual Dimorphism
  • male more colorful
  • sexes shaped differently

Development

Sticky threads anchor the eggs of triplefin blennies to algae in the nest site. After hatching, larvae in species of Tripterygion settle after approximately 40 days. One study indicates that larvae are affected by auditory cues (reef sounds) in determining where to settle. (Myrberg and Fuiman, 2002; Thresher, 1984)

Reproduction

Male triplefin blennies establish territories on rocks covered with algae. From this vantage point they signal to passing females by “loop-swimming,” a courtship motion that varies from species to species, but entails quickly hopping up and down in a loop. Males of species in Axoclinus pose before loop-swimming, resting on their pelvic fins and waving the caudal fin, which gives the female a better chance to view his courtship colors. One male may spawn with several females. (Thresher, 1984)

Definitive information about spawning seasons of triplefin blennies is lacking, but spawning likely occurs year-round in the tropics and during warmer seasons in temperate areas. In order to spawn the male first cleans the algal filaments at the nest site, and then attracts one or more females to the nest. Spawning can last up to several hours. Eggs are deposited by the female one at a time and fertilized simultaneously by the male, with clutch sizes sometimes reaching 500 eggs. “Streaking” occurs in some species of Tripterygion and Axoclinus: smaller, most likely younger, cryptically-colored males rush in while the dominant male is engaged in spawning, releasing their own sperm in an attempt to fertilize some of the eggs. (Thresher, 1984)

Male triplefin blennies remain near the eggs to guard them until they hatch. (Thresher, 1984)

Lifespan/Longevity

No information was found regarding the lifespan of Tripterygiidae.

Behavior

Most recorded behavior of triplefin blennies has to do with their reproductive habits (see Reproduction: Mating Systems and General Behavior). Otherwise, they frequent hidden, shadowy areas, darting to and fro with intermittent pauses. One species, Bellapiscis medius, can crawl out of low-oxygen tidepools to breathe air, although it does not have a specialized air-breathing organ. (Graham, 1997; Wheeler, 1985)

Communication and Perception

No information was found on communication in Tripterygiidae, except regarding courtship displays by males (see Reproduction: Mating Systems).

Food Habits

Triplefin blennies feed on algae and tiny invertebrates. (Allen and Robertson, 1994)

Predation

Triplefin blennies avoid predators by attempting to remain unnoticed. They are small, occupy hiding places in the reef, and are cryptically colored or partially transparent. (Allen and Robertson, 1994; Thresher, 1984)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Triplefin blennies have in many cases adapted to specialized local conditions, so they may occupy otherwise unfilled roles in certain areas. They feed on and thereby impact populations of small invertebrates, and likewise may affect algal growth. (Allen and Robertson, 1994; Wheeler, 1985)

Economic Importance for Humans: Positive

Some triplefin blennies are kept in aquaria, but none are considered sport or food fishes. (Wheeler, 1985)

Economic Importance for Humans: Negative

No specific information was found concerning any negative impacts to humans.

Conservation Status

Currently, there is no known conservation threat to any member of this family. (The World Conservation Union, 2002)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Monica Weinheimer (author), Animal Diversity Web.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

herbivore

An animal that eats mainly plants or parts of plants.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pet trade

the business of buying and selling animals for people to keep in their homes as pets.

planktivore

an animal that mainly eats plankton

polygynous

having more than one female as a mate at one time

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

References

Allen, G., D. Robertson. 1994. Fishes of the Tropical Eastern Pacific. Honolulu, HI: University of Hawaii Press.

Böhlke, J., C. Chaplin. 1994. Fishes of the Bahamas and Adjacent Tropical Waters. Wynnewood, Pa: Published for the Academy of Natural Sciences of Philadelphia by Livingston.

Graham, J. 1997. Air-Breathing Fishes: Evolution, Diversity, and Adaptation.. San Diego, CA: Academic Press.

Helfman, G., B. Collete, D. Facey. 1997. The Diversity of Fishes. Malden, MA: Blackwell.

Myrberg, A., L. Fuiman. 2002. The Sensory World of Coral Reef Fishes. Pp. 123-148 in P Sale, ed. Coral Reef Fishes: Dynamics and Diversity in a Complex Ecosystem. San Diego, CA: Academic Press.

Nelson, J. 1994. Fishes of the World – third edition. Upper Saddle River, NJ: Prentice-Hall.

Springer, V. 1998. Blennies. Pp. 217 in W Eschmeyer, J Paxton, eds. Encyclopedia of Fishes – second edition. San Diego, CA: Academic Press.

The World Conservation Union, 2002. "IUCN 2002" (On-line). IUCN Red List of Threatened Species. Accessed August 02, 2003 at http://www.iucnredlist.org/.

Thresher, R. 1984. Reproduction in Reef Fishes. Neptune City, NJ: T.F.H. Publications.

Wheeler, A. 1985. The World Encyclopedia of Fishes - second edition. London: Macdonald.