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Etheostoma barbouriTeardrop darter

By Dana Campbell

Geographic Range

Teardrop darters are an endemic species of the middle and upper portions of the Green River system in Kentucky and Tennessee from 38ºN to 36ºN (Kuehne and Small, 1971). (Kuehne and Small, 1971)

Habitat

Teardrop darters are found in the freshwater aquatic drainage of the Green River in the temperate region of Kentucky and Tennessee. They are located in small to medium upland streams that are 2nd, 3rd, and 4th order tributaries. Adults are mostly collected in areas less than 0.66 meters deep and sometimes in pools of up to 1 meter deep and rarely seen in riffles (Kuehne and Small, 1971). Fry on the other hand have been found to occupy slow riffles and just below them (Flynn and Hoyt, 1971). They are flat rock bottom dwellers in low density of vegetative cover along sandy banks. Adults inhabit water with temperatures ranging from 21 to 27 degrees Celsius, whereas, eggs and larvae are found in water temperatures below 15 degrees Celsius (Tennessee Animal Biogeographic System Tabs, 2002). ("Tennessee Animal Biogeographic System Tabs", 12/2002; Flynn and Hoyt, 1979; Kuehne and Small, 1971)

  • Aquatic Biomes
  • benthic
  • rivers and streams
  • Range depth
    .33 to 2.66 m
    1.08 to 8.73 ft
  • Average depth
    .66 m
    2.17 ft

Physical Description

Teardrop darters are divided into three age classes with a standard length of about 3 cm, 4 cm, and 4.5 cm. They are considered fully mature at 4.5 cm and weighing about 2.7 grams. They are bar checked darters and can be distinguished from the others by a darker sub orbital pigment bar, nine preoperculomandibular pores and less infraorbital and lateral line pores (Flynn and Hoyt, 1979). The Tennessee Animal Biogeography System website describes them as a slender fish having an incomplete lateral line with a count of 41 to 46 scales, 8 to 9 dorsal spines with dorsal ray counts of 12 to 14, and 2 anal spines with 8 to 9 anal rays. Teardrop darters are yellow with hints of orange, a dark head with a black bar by the eye, and black blotches on the body. They have dots on the caudal, anal, and second dorsal fins but the first dorsal fin is stripped and the pelvic fin is white to match the breast and belly. ("Tennessee Animal Biogeographic System Tabs", 12/2002; Flynn and Hoyt, 1979)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    2.7 (high) g
    0.10 (high) oz
  • Range length
    3 to 4.5 cm
    1.18 to 1.77 in
  • Average length
    4 cm
    1.57 in

Development

Eggs develop in 15 to 22 days depending on temperature. Fry can be found starting in late May with a standard length of 15 mm. Age can be determined by their scale annuli. Teardrop darters are divided into three age groups. After one year they reach a standard length of 31.9 mm and grow to 47.1 mm after reaching two years of age. (Flynn and Hoyt, 1979)

Reproduction

In teardrop darters, the sexes do not differ in appearance although males show a darkening through spawning season and after. Flynn and Hoyt (1979) also observed that there were no breeding tubercles, but females did have some inflammation in the genital papillae during spawning. (Flynn and Hoyt, 1979)

Males clear out areas underneath the rock with just enough room for the fish to fit with a fanning of their tail. One the nest site is ready, males will chase females into the site by bumping them. Both males and females invert their body during spawning. (Flynn and Hoyt, 1979)

Spawning season is April through May depending on the time it takes for the gonads to develop (Flynn and Hoyt, 1979). Each female lays 17 to 48 eggs (Flynn and Hoyt, 1979) underneath a flat stone monolayer with several using the same nest site (Page et al. 1982), and as many as 70 in one spot. Sexual maturity is complete at the end of the first year. Kuehne and Small (1971) describe reproduction as having a high resilience because the population can double in under fifteen months. Males have a yellowish growth on the dorsal fin in breeding season resembling an egg thought to compel females to lay eggs because females tend to select spots where others have deposited eggs earlier. (Etnier and Starnes, 2001; Flynn and Hoyt, 1979; Page and Burr, 1982; Etnier and Starnes, 2001; Flynn and Hoyt, 1979; Page and Burr, 1982)

  • Breeding interval
    Breeding occurs once yearly.
  • Breeding season
    Spawning season is April through May depending on the time it takes for the gonads to develop(Flynn and Hoyt, 1979).
  • Range number of offspring
    17 to 48
  • Range time to hatching
    125 to 270 hours
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Males have been observed guarding nests (Etnier and Starnes, 2001). It is not clear whether males are protecting young or just waiting for another mating opportunity since females prefer to lay eggs in established sites. Males have been observed eating fry. (Etnier and Starnes, 2001)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • male

Lifespan/Longevity

The age of teardrop darters can be detected by size or annulus formation. The maximum life span reported is two and a half years (Etnier and Starnes, 2001). Females rarely live to two years of age (Flynn and Hoyt, 1979). (Etnier and Starnes, 2001; Flynn and Hoyt, 1979)

  • Typical lifespan
    Status: wild
    2.5 (high) years
  • Average lifespan
    Status: wild
    2 years
  • Average lifespan
    Status: captivity
    2 years
    AnAge

Behavior

Males will defend their territory from other competing males, chasing them off.

Home Range

There is no information available on home range in this species.

Communication and Perception

Darters can produce a chemical, fright substance in the water to deter predators. (Etnier and Starnes, 2001)

Teardrop darters use their vision, tactile senses, and chemoreception to perceive their environment. (Etnier and Starnes, 2001)

Food Habits

Teardrop darters are carnivores. Their diet throughout life includes many different aquatic macroinvertebrates and occasionally detritus. Some of the most important food items for teardrop darters are the larval and adult stages of Diptera, Ephemeroptera larva, and Copepoda adults. (Flynn and Hoyt, 1979)

  • Animal Foods
  • insects
  • aquatic crustaceans

Predation

Besides being eaten by other teardrop darters, some predators include grass pickerel (Esox americanus), banded sculpin (Cottus carolinae), water snakes (Nerodia), snapping turtles (Chelydra serpentina), belted kingfishers (Megaceryle alcyon), and little green herons (Egretta caerulea). (Flynn and Hoyt, 1979)

Teardrop darters hide and rely on their agility to deter predators. (Flynn and Hoyt, 1979)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

The carnivorous diet, small body size, and short life span are the major factors in the teardrop darters' ecosystem roles. They are found to share the same area with the spottail darters (Etheostoma squamiceps). (Flynn and Hoyt, 1979)

Commensal/Parasitic Species
  • Black spot parasites, Crassihpiala bulboglessa
  • Nematodes are found in the mesenteries of the body cavity.

Economic Importance for Humans: Positive

Teardrop darters contribute to the diversity and enhance the beauty of the Green River basin. Teardrop darters could potentially have a greater importance to humans not currently understood.

  • Positive Impacts
  • research and education

Economic Importance for Humans: Negative

Teardrop darters have no negative impact on humans.

Conservation Status

Tennessee Wildlife Resources Agency (2002) has teardrop darters listed in non-game species in need of management. They are otherwise not listed as threatened or endangered. (Myers, 2002)

Other Comments

Etheostoma virgatum and Etheostoma obeyense are the closest relatives of teardrop darters. They seem to be allopatric species. (Kuehne and Small, 1971)

The teardrop darter was named after Professor Roger W. Barbour from the University of Kentucky. (Kuehne and Small, 1971)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Dana Campbell (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

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.

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.

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

diurnal
  1. active during the day, 2. lasting for one day.
ectothermic

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

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

insectivore

An animal that eats mainly insects or spiders.

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.

oviparous

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

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

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

visual

uses sight to communicate

References

12/2002. "Tennessee Animal Biogeographic System Tabs" (On-line). Accessed October 19, 2005 at fwie.fw.vt.edu/TN/TN00077.htm.

Etnier, D., W. Starnes. 2001. The Fishes of Tennessee.. Knoxville: The University of Tennessee Press.

Flynn, R., R. Hoyt. 1979. The life history of the teardrop darter. The American Midland Naturalist, 101: 127-141.

Kuehne, R., J. Small. 1971. Etheostoma barbouri, a new darter (Percidar, Etheostomatini) from the Green River with notes on the subgenus Catonotus.. Copeia: 18-26.

Myers, G. 2002. "Tennessee Wildlife Resources Agency" (On-line). Accessed November 22, 2005 at http://www.state.tn.us/tura/nong002.

Page, L., B. Burr. 1982. Three new species of darters (Percidae, Ethepstoma) of the subgenus Nanostoma from Kentucky and Tennessee.. Occ. Pap. Mus. Nat. Hist. Univ. Kans., 101: 1-20.

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