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).
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).
- Habitat Regions
- temperate
- freshwater
- Aquatic Biomes
- benthic
- rivers and streams
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.
- Other Physical Features
- ectothermic
- heterothermic
- bilateral symmetry
- Sexual Dimorphism
- sexes alike
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.
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.
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.
- Mating System
- polygynous
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.
- Key Reproductive Features
- iteroparous
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- oviparous
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.
- Parental Investment
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
protecting
- male
-
protecting
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).
Behavior
Males will defend their territory from other competing males, chasing them off.
- Key Behaviors
- natatorial
- diurnal
- motile
- sedentary
- solitary
- territorial
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.
Teardrop darters use their vision, tactile senses, and chemoreception to perceive
their environment.
- Communication Channels
- chemical
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.
- Primary Diet
- carnivore
- Animal Foods
- insects
- aquatic crustaceans
- Other Foods
- detritus
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
).
Teardrop darters hide and rely on their agility to deter predators.
- 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
).
- 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.
Other Comments
Etheostoma virgatum
and
Etheostoma obeyense
are the closest relatives of teardrop darters. They seem to be allopatric species.
The teardrop darter was named after Professor Roger W. Barbour from the University
of Kentucky.
Additional Links
Contributors
Tanya Dewey (editor), Animal Diversity Web.
Dana Campbell (author), Eastern Kentucky University, Sherry Harrel (editor, instructor), Eastern Kentucky University.
- 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.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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).
- freshwater
-
mainly lives in water that is not salty.
- 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.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- 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.
- 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.
- polygynous
-
having more than one female as a mate at one time
- 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).
- seasonal breeding
-
breeding is confined to a particular season
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- fertilization
-
union of egg and spermatozoan
- external fertilization
-
fertilization takes place outside the female's body
- oviparous
-
reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.
- natatorial
-
specialized for swimming
- diurnal
-
- active during the day, 2. lasting for one day.
- motile
-
having the capacity to move from one place to another.
- sedentary
-
remains in the same area
- solitary
-
lives alone
- 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
- chemical
-
uses smells or other chemicals to communicate
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- chemical
-
uses smells or other chemicals to communicate
- detritus
-
particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).
- 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.
- carnivore
-
an animal that mainly eats meat
- insectivore
-
An animal that eats mainly insects or spiders.
References
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.
12/2002. "Tennessee Animal Biogeographic System Tabs" (On-line). Accessed October 19, 2005 at fwie.fw.vt.edu/TN/TN00077.htm .