By Jamie Alton
Geographic Range
Bluntnose darters, Etheostoma chlorosomum, are primarily found in the Mississippi River drainage basin. They may also be found in the Mobile Bay drainage and San Antonio River drainage basin. (Page and Burr, 2005)
Habitat
Bluntnose darters are typically found in sandy, slow running, shallow water. They also can be found occupying areas with scattered debris. Substrates that are somewhat firm also provide a good habitat for bluntnose darters. (Etnier and Starnes, 1993)
These animals are found in the following types of habitat:
freshwater 
.
Physical Description
(1.5 to 1.81 in)
Bluntnose darters are pale yellow with a translucent look to them. They have blunt noses and five to six small dorsal saddles. They are also identified by having several small brown “W”’s and “X”’s spread randomly throughout the side of the body. Dorsal and caudal fins are speckled with brown . The suborbital bar is usually present as well as the preorbital bar. The preorbital bar is a distinguishing factor in determining bluntnose darters from Johnny darters, Etheostoma nigrum which are similar in appearance. The preorbital bar connects in the bluntnose darter in contrast to the johnny darter where it does not. The anal fin has one spine and 7-9 soft rays (Etnier and Starnes 1993). The dorsal fin has 8-10 spines and 10-11 soft rays and the caudal fin consists of 13-17 rays. The lateral line is incomplete with a lateral line count of 51-60. The species name E. chlorosoma is broken down chloro = green, soma = body. This name can be misleading because green may only be seen faintly on good specimens. Bluntnose darters can reach a length of 38 to 46 mm during adult stages of life. Males and females appear similar outside of the breeding season, but are sexually dichromatic during the breeding season. ("Wisconsin Department of Natural Resources", 2003; Etnier and Starnes, 1993)
Some key physical features:
ectothermic ; heterothermic ; bilateral symmetry .
Sexual dimorphism: sexes alike, sexes colored or patterned differently.
Development
Bluntnose darters start out with an embryonic period, which begins at fertilization. They advance to a larval period when they are able to capture food. Once the organ systems are formed, they enter the juvenile period. They are finally classified as adults when they are able to reproduce (i.e., when gonads become mature). (Moyle and Cech, 2004)
Reproduction
Bluntnose darters breed seasonally each year.
They lay their eggs in April or May when the water temperature is suitable for their reproduction success
Bluntnose darters are polygynandrous, where females go from one male to the other to maximize their reproductive success. They show dichromatism during the breeding season. Dichromatism is when the species changes color when it is time to attract a mate. During the breeding season males become darker on their belly, dorsal fin, and pelvic fins. They also develop sharp tubercles on the soft rays of their anal and pelvic fins. These breeding tubercles are tiny hard bumps of keratin. While the male courts the female with these rituals, the female usually chooses where to lay the eggs. (Etnier and Starnes, 1993; Moyle and Cech, 2004; Shiels, 2005)
Mating systems:
polygynandrous (promiscuous) .
Bluntnose darters are nest spawners. Females select suitable places where the eggs are deposited and fertilized. They use plants or plant debris as suitable places to lay their eggs. They lay their eggs in April or May when the water temperature is suitable for their reproduction success. They usually attach one to three eggs per spawning act. Territoriality is seen in bluntnose darters because they spend time in one specific place guarding the embryo or defending the area. They also show elaborate courtship behaviors. This is shown by the males during breeding season with their elaborate coloration. Females usually produce 230-1000 eggs per reproductive effort. They usually reach maturity at one year of age. (Etnier and Starnes, 1993; Shiels, 2005)
Key reproductive features:
iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (external ); oviparous .
Parental care is provided by the male. This could be due to the greater parental investment the female has in gonadal development when compared to the smaller investment the males make (i.e., sperm vs. ova). Females usually abandon eggs to search for more breeding opportunities. Females have been known to spawn many times during the reproductive season. (Moyle and Cech, 2004; Shiels, 2005)
Parental investment:
pre-fertilization (provisioning, protecting: female); pre-hatching/birth (provisioning: female, protecting: male).
Lifespan/Longevity
Bluntnose darters lifespan may be cut short by siltation from agricultural runoff. Their habitat in shallow water can also limit their life when creeks dry up during periods of drought. No exact numbers were found on bluntnose darters. However in the closely related Johnny darters, Etheostoma nigrum, suggested lifespan is 3 years. ("Kentucky AWAKE", 2005; "Wisconsin Department of Natural Resources", 2003)
Behavior
No specific behavioral information was found on bluntnose darters. However Johnny darters, Etheostoma nigrum, have no swimbladder so they are benthic dwelling. They can dart around from rock to rock with quick bursts of speed. (Shiels, 2005)
Home Range
There is no information on home range in bluntnose darters. (Etnier and Starnes, 1993)
Key behaviors:
natatorial ; motile ; sedentary ; solitary ; territorial .
Communication and Perception
Darters communicate by coloration during breeding seasons. This coloration is used to attract the opposite sex. (Etnier and Starnes, 1993)
Communicates with:
visual .
Food Habits
Bluntnose darters are invertivores. Bluntnose darters feed on minute freshwater organisms such as chironomid, blackfly larvae, Cyclops species, and Daphnia species. ("NatureServe Explorer", 2005; "Wisconsin Department of Natural Resources", 2003; Froese and Pauly, 2005)
Primary Diet:
carnivore (insectivore , eats non-insect arthropods).
Animal Foods:
insects; aquatic crustaceans.
Predation
- larger, predatory fish (Actinopterygii)
Bluntnose darters are small and are likely to be prey for larger species of fish. During the non-breeding season they are light tan with dark brown blotches. This color pattern may provide camouflage from potential predators against the bottom of creeks and streams. (Etnier and Starnes, 1993)
Anti-predator adaptations::
cryptic .
Ecosystem Roles
No specific information was found on bluntnose darters. However darters may have an commensal relationship with freshwater mussels. Commensal relationships occur when one species benefits from the relationship while the other is not affected. They may be integral in the reproductive cycle by having glochidia attach to their gills. (Shiels, 2005)
Economic Importance for Humans: Negative
Bluntnose darters have no adverse affects on humans.
Economic Importance for Humans: Positive
There is no direct benefit bluntnose darters have toward humans.
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
Bluntnose darters are threatened in several states along the Mississippi River and adjacent drainages. According to NatureServe Explorer (
http://www.natureserve.org/explorer/), bluntnose darters in Kansas are presumed extirpated, in Wisconsin they are critically imperiled, in Kansas they are imperiled, in Indiana they are vulnerable. Bluntnose darter populations are apparently secure in Kentucky, Illinois, Minnesota, Missouri, Arkansas, Oklahoma, Texas, Tennessee, Alabama, Mississippi, and Louisiana. Their decline could be caused by siltation resulting from agricultural runoff and creeks drying up during periods of drought. ("NatureServe Explorer", 2005; "Wisconsin Department of Natural Resources", 2003)
Contributors
Tanya Dewey (editor), Animal Diversity Web, University of Michigan Museum of Zoology.
Jamie Alton (author), Eastern Kentucky University. Sherry Harrel (editor, instructor), Eastern Kentucky University.
