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Etheostoma micropercaLeast darter

By Beth Keskey

Geographic Range

Least darters inhabit the Great Lakes and the Mississippi River Basin in the northern United States, as well as southern Ontario in Canada. They are also found in western Ohio, Illinois and Indiana, and in isolated areas of Oklahoma, Arkansas, Kansas and Missouri. ("Least darter (Etheostoma microperca)", 2003; Jordan and Gilbert, October 2010; Jordann and Gilbert, 2012; "Etheostoma microperca", February 2009)

Habitat

Least darters thrive in bodies of water in temperate boreal forests and temperate grasslands. Grassland temperatures can range from -40 degrees F to 100 degrees F. Both of these biomes have relatively short summers and long winters. The aquatic environment that least darters require consists of sandy-bottomed streams and areas of dense vegetation. Organic sediments and silt are also preferred. Least darters require slow moving freshwater streams, ponds, and rivers that have dense vegetation. This habitat provides refuge from predators and a safe place for spawning. They choose shallow pools for optimal survival of offspring during the spawning season. After spawning, least darters return to deeper waters. ("Least darter (Etheostoma microperca)", 2003; Hatch, 1986; Johnson and Hatch, 2001)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • Average elevation
    1000 m
    3280.84 ft

Physical Description

Least darters are part of the perch family. They are differentiated from other closely related species by their small size and species-specific coloration. Least darters appear much longer than they are wide, and their bodies are small and compressed. Their ctenoid scales are rough in texture. They are light olive in color with 6 to 12 black blotches along their spine. Several dark radiating lines can be observed originating from the eyes. Females are slightly larger than males. Females in the breeding season have yellow fins, while males develop orange or red spots on the dorsal fins. Male pelvic fins also become flushed with hues of red and orange. ("Least darter (Etheostoma microperca)", 2003; "Perches", 2012; "Least Darter", 2012; Hatch, 1986; Jordan and Gilbert, October 2010; Jordann and Gilbert, 2012)

Darker coloration on the spine of least darters known as counter-shading helps them blend into the habitat when viewed from above. The black blotches located on the spine are an example of coloration disruption. This allows the fish to blend in with their surroundings. This adaptation allows for predator evasion. ("Least Darter", 2012; Hatch, 1986; Johnson and Hatch, 2001)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    0.20 to 0.38 g
    0.01 to 0.01 oz
  • Range length
    3.1 to 4.4 cm
    1.22 to 1.73 in
  • Average length
    4 cm
    1.57 in

Development

Male and female least darters grow at the same rate. They reach an average of 29 mm after one year and grow to approximately 34 mm by the second spawning season. Once fully developed, females are generally larger than males. (Hatch, 1986)

Reproduction

The breeding season of least darters depends on location. In the southern regions of the United States, spawning begins in February. In northern regions from Illinois to Minnesota up into southern Canada, the mating season begins in late May and continues to late July. Males locate a territory of 5 to 10 cm and include one or two plants. In wild populations, territories have been observed as large as 30 cm. Males chase rival fish from their territory. This behavior usually consists of head-to-tail nudging. Once a female enters a male's territory for the purpose of mating, she approaches the vegetation. The males grasps her back with his pelvic fins, encouraging her to release her eggs. Immediately after she releases her eggs, males release milt to fertilize them. Females mate with multiple males. ("Least darter (Etheostoma microperca)", 2003; Cordes and Page, 1980; Hatch, 1986; "Etheostoma microperca", February 2009)

During the spawning season, least daters undergo changes to make them more attractive to mates. They turn a darker green color and black blotches appear more visible. The anal fin and pelvic area turn a bright orange, while the dorsal and caudal fins turn a white color banded with gray. ("Least darter (Etheostoma microperca)", 2003; Cordes and Page, 1980; Hatch, 1986; "Etheostoma microperca", February 2009)

Least darters reach sexual maturity by the first spring after hatching. Males locate a territory and defend it from other males. Spawning begins once a female enters a male's territory. Males swim in a ritual-like fashion to entice the female to copulate. The female attaches her eggs to an aquatic substrate and exits the territory. Paternal care continues as the males remain territorial over the fertilized egg clutch. The eggs of a first-year spawning female are usually small and opaque white in color. Little to no parental care is given to the offspring. Males protect the eggs for a period of time after fertilization, but may leave before hatching in attempt to fertilize the clutch of another female. (Cordes and Page, 1980; Dalton, 1990; Hatch, 1986; Paine, et al., 1982)

  • Breeding interval
    Least darters breed once per year and have 3 clutches.
  • Breeding season
    Least darters breed from May to late July.
  • Range number of offspring
    80 to 200
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

No maternal care is observed after spawning. Paternal care consists of territory protection until eggs hatch. Closely related darters (Percidae) either display paternal care or non-parental care. The paternal care shown by the least darter has been speculated to have evolved 3 separate times throughout the evolution of the darter family. (Hatch, 1986; Kelly, et al., May 2012)

Lifespan/Longevity

Most least darters do not survive past the first breeding season, and live only 13 to 14 months. Almost all that live a second year die shortly afterwards. However, 3-year-old least darters have been reported in the wild. Least darters in captivity tend to live longer. (Hatch, 1986)

  • Average lifespan
    Status: wild
    3 years
  • Range lifespan
    Status: captivity
    0 to 3 years
  • Average lifespan
    Status: captivity
    2 years
  • Typical lifespan
    Status: wild
    13 to 14 months
  • Average lifespan
    Status: captivity
    2 years

Behavior

Least darters migrate from deeper streams to shallower, weedy streams between March and May. Least darters are territorial, and aggression is most commonly observed by males during the spawning season. ("Least Darter", 2012; Hatch, 1986; Johnson and Hatch, 2001)

  • Range territory size
    5 cm to 30 cm cm^2
  • Average territory size
    10 cm cm^2

Home Range

The home range of least darters in unknown. (Hatch, 1986; Jordann and Gilbert, 2012; "Etheostoma microperca", February 2009)

Communication and Perception

Fish in the perch family (Percidae) are able to see and hear as well as detect vibrations in the water. Evidence for vision comes from female mate selection during the spawning season. Males with brighter coloration have a higher success rate at attaining a mate. ("Least darter-Etheostoma microperca", 2004; "Least darter (Etheostoma microperca)", 2003; "White Perch", 2002)

  • Communication Channels
  • visual

Food Habits

The diet of least darters consists of micro-crustaceans, aquatic invertebrate larvae, copepods (Copepoda) and water fleas (Cladocera). (Hatch, 1986; Jordann and Gilbert, 2012)

  • Primary Diet
  • carnivore
    • eats non-insect arthropods
  • Animal Foods
  • insects
  • aquatic crustaceans
  • other marine invertebrates
  • zooplankton

Predation

Predators of least darters include turtles (Testudines), birds, and larger fish. Depending on the location and fauna in the area the predation rate of least darters varies. However, due to their preference for high vegetation, they avoid many predators. ("Least darter (Etheostoma microperca)", 2003)

Ecosystem Roles

Least darters are both predators and prey in their ecosystem. They are not known to become infected with any parasites.

Economic Importance for Humans: Positive

Least darters do not provide any known economic benefits for humans. (Hatch, 1986)

Economic Importance for Humans: Negative

Least darters do not have any known negative impacts on humans.

Conservation Status

Least darter populations are in decline, though they are not formally recognized as threatened or endangered. Their conservation status is not evaluated by the IUCN Red List of Threatened Species. Major concerns to their population include habitat loss, pollution, invasive species, agricultural pesticides and deforestation. Efforts to conserve them are gaining recognition. In southern Minnesota, least darter populations were surveyed by the DNR and older populations have gone extinct due to anthropogenic development. New sites have been discovered in Minnesota; however, no plans have been established to mitigate the decline. In 2008, a conservation budget proposal in Arkansas listed objectives including monitoring population size, investigating extinction causes, and determining survival status and distribution. Their population is at risk because they are small fishes with a high dispersal between populations. ("Least darter-Etheostoma microperca", 2004; "Targeting and facilitating conservation efforts for two Arkansas darters: Etheostoma cragini and E. microperca.", 2008; Jordann and Gilbert, 2012)

Contributors

Beth Keskey (author), Minnesota State University, Mankato, Robert Sorensen (editor), Minnesota State University, Mankato, Catherine Kent (editor), Special Projects.

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

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

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

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

freshwater

mainly lives in water that is not salty.

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).

male parental care

parental care is carried out by males

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.

polyandrous

Referring to a mating system in which a female mates with several males during one breeding season (compare polygynous).

sedentary

remains in the same area

sexual

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

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

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

NatureServe Explorer. February 2009. Etheostoma microperca. An Online Encyclopedia of Life, 7.1 Edition. NatureServe. Accessed February 08, 2012 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Etheostoma%20microperca.

Department of Natural Resources. 2012. "Least Darter" (On-line). ODNR Division of Wildlife. Accessed March 04, 2012 at http://dnr.state.oh.us/Home/species_a_to_z/leastdarter/tabid/21861/Default.aspx.

ARKive. 2003. "Least darter (Etheostoma microperca)" (On-line). ARKive Imagines of Life on Earth. Accessed February 08, 2012 at http://www.arkive.org/least-darter/etheostoma-microperca/#text=Description.

2004. "Least darter-Etheostoma microperca" (On-line). Iowa Fish Atlas. Accessed April 03, 2012 at http://maps.gis.iastate.edu/iris/fishatlas/IA168411.html.

Commonwealth of Pennsylvania. 2012. "Perches" (On-line). Gallery of Pennsylvania Fishes. Accessed April 03, 2012 at http://fishandboat.com/pafish/fishhtms/chap23.htm.

2008. "Targeting and facilitating conservation efforts for two Arkansas darters: Etheostoma cragini and E. microperca." (On-line). Accessed April 03, 2012 at http://www.wildlifearkansas.com/proposals/2008Preproposals/Arkansas%20Darter%20and%20Least%20Darter%20conservation.pdf.

University of Michigan. 2002. "White Perch" (On-line). Critter Catalogue. Accessed March 04, 2012 at http://www.biokids.umich.edu/critters/Morone_americana/.

Cordes, L., L. Page. 1980. Feeding chronology and diet composition of two darters (Percidae) in the Iroquois River System, Illinois. American Midland Naturalist, 104: 202-204.

Dalton, K. 1990. Status of the Least Darter, Etheostoma microperca , in Canada. Canadian Field-Naturalist, 104: 53-58.

Hatch, J. 1986. Life History of the Least Darter in Dinner Creek, Becker County, Minnesota. Conservation Biology Research Grants Program. Accessed February 08, 2012 at http://files.dnr.state.mn.us/eco/nongame/projects/consgrant_reports/1986/1986_hatch2.pdf.

Johnson, J., J. Hatch. 2001. Life History of the Least Darter Etheostoma microperca at the Northwestern Limits of its Range. American Midland Naturalist, 125: 87-103. Accessed February 08, 2012 at http://www.jstor.org/stable/10.2307/2426372.

Jordan, , Gilbert. October 2010. "Etheostoma microperca" (On-line). Accessed February 08, 2011 at http://www.fishbase.org/summary/speciessummary.php?id=3441.

Jordann, , Gilbert. 2012. "Etheostoma microperca" (On-line). Minnesota Department of Natural Resources. Accessed March 26, 2012 at http://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=AFCQC02450.

Kelly, N., T. Near, S. Alonzo. May 2012. Diversification of egg-deposition behaviours and the evolution of male parental care in darters (Teleostei: Percidae: Etheostomatinae). Journal of Evolutionary Biology, 25/5: 836-846.

Paine, M., J. Dodson, G. Power. 1982. Habitat and food resource partitioning among four species of darters (Percidae: Etheostoma ) in a southern Ontario stream. Canadian Journal of Zoology, 60: 1635-1641.

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