Fundulus sciadicus

Geographic Range

Plains topminnows ( Fundulus sciadicus ) are small minnows that are found in several microhabitats of the Nearctic region. They are found in the northern and western margins of the Ozarks from Lost and Shoal Creeks in southwestern Missouri and into direct tributaries of the Missouri River. They are also found in Nebraska, northeastern Colorado, eastern Wyoming, southern South Dakota, northeastern Oklahoma, in the Red River in Minnesota, and in western Iowa.

Plains topminnows have the most limited range of all of the Fundulus species due to their habitat requirements. Attempts have been made to reintroduce plains topminnows into several rivers in Missouri, where they are believed to have been historically extant.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
  • native native

Habitat

Plains topminnows seem to prefer shallow waters with little or no current that have sandy substrates and abundant vegetation. Evidence suggests that sandy locations with vegetation are important for nesting behavior. Vegetation provides cover from potential predators and prevents the eggs from washing downstream. Plains topminnows also gravitate towards areas that are sheltered from the wind and lakes featuring gradually sloping bottoms.

Plains topminnows generally prefer to live near the water's surface. This provides a much higher oxygen content, as well as the ability to avoid predators. Plains topminnows cannot survive in distilled water, which may be an adaptation due to human development. They are adapted to freshwater and slightly saline water, allowing them the ability to live in slightly brackish water. They are also very dependent on the area to which they are individually adapted. Due to habitat fragmentation from ditching and draining of rivers, lakes, and streams, they tend to specialize in their own form of water only and can not be transported from habitat to habitat very well.

• Habitat Regions
• temperate temperate
• freshwater freshwater

• Aquatic Biomes
• lakes and ponds
• rivers and streams
• temporary pools
• brackish water brackish water

• Other Habitat Features
• estuarine estuarine

Physical Description

Outside the breeding season, female and male plains topminnows have identical dark green coloration with black sides and silvery white stomachs. During the breeding season, the female's color does not change while the male adopts an orange and yellow belly, presumably to attract a mate. Most of the year, their fins lack vertical bars or other distinct markings. Adult plains topminnows have one dorsal and one anal fin. The anal fin rays are 12 to 14 inches long with 12 to 15 spines. The dorsal fin rays, however, are shorter at 10 to 11 inches with 9 to 12 spines. The heads of plains topminnows are broad and flat, giving their mouth an upturned look. Due to their small size, they are not adapted for sustained swimming in high currents, even though this is necessary to move through drainage networks to recolonize new habitats after a severe drought.

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes colored or patterned differently
• male more colorful

Development

Plains topminnows are viviparous. Females lay many eggs with a coating of mucus around them and oil inside, which provides nutrients. Gestation typically lasts 8 to 10 days. Eggs most likely hatch once the water temperature reaches 21 degrees Celsius. Newly hatched minnows are approximately 7.6 mm in length. Minnows feed immediately on the first day out of the egg, and develop predator avoidance techniques 2 to 4 days after hatching. Only 0.42% of the eggs will survive to maturity. Plains topminnows exhibit indeterminate growth.

• Development - Life Cycle
• indeterminate growth indeterminate growth

Reproduction

The mating strategy of plains topminnows is similar to other members of the Fundulus genus. The breeding season occurs between May and June. The water temperature needs to be around 21 degrees Celsius before spawning can occur. Females mostly decide mates, determined by competition among males. Two males line up next to each other and swim in circles until one of the males ends up biting the tail of the other male. The female witnesses this display, and then proceeds to swim very closely to the ground. This allows her anal fin to dig into the sand, which creates a place for her to deposit her eggs. Once this small trench is dug, she swims back and deposits her unfertilized eggs into the trench. The male then immediately swims past her eggs, depositing sperm onto them. This system ensures that most of the eggs are fertilized by the dominant male. Satellite males swim by after the first male and fertilize the remainder of the eggs. This is a very effective method for reproduction that creates only a small chance that the eggs will wash downstream and not survive. Males also have multiple mates. Although mating behavior in plains topminnows has been observed extensively, it is only speculated that it is what causes the female to mate with the male. This is a result of laboratory observation, where no deposition of eggs have been observed, despite eggs being found after this behavior happens.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Plains topminnows breed once a year in early spring and summer. Females lay many eggs with a coating of mucus around them and oil inside. The eggs are sealed from the outside and none of their chemicals leach out into the environment. They are surrounded in mucous that attaches the eggs to vegetation. The oil inside the egg is used for sustenance until the egg hatches. Eggs laid in warmer water have a thinner coat of mucus, and this mucus layer becomes thicker as water temperature increases. There is also a strong positive correlation between the age of the mother and the amount of oil and mucus produced. Older minnows produce more, and presumably their eggs have a higher survival rate. Of the 200 to 400 eggs that are laid, only about 25 to 50 eggs survive to birth as a result of the low level of parental care. Only about 0.42% survive to maturity.

Gestation typically lasts 8 to 10 days. Eggs most likely hatch when the water temperature is at 21 degrees Celsius. When the minnows hatch, they are approximately 7.6 mm long. The minnow immediately feeds on the first day out of the egg, and develops predator avoidance techniques 2 to 4 days after hatching.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • external external
• oviparous oviparous

Females provide the egg with mucus so it can adhere to the ground and the vegetation where it is laid. Inside of the mucus coating, there is an oil that is used as a nutrient source for development of the embryo. After eggs are laid, their is no additional investment by either parent.

• Parental Investment
• female parental care female parental care
• pre-fertilization
  • provisioning
  • protecting
    • female

Lifespan/Longevity

Plains topminnows have been identified that are 4 years of age, even though they were not tracked from juvenile stages to adult stages.

Behavior

There are typically low numbers of adult plains topminnows, which suggests low levels of intraspecific competition. There appears to be an increase in observations and activity of this minnow when the temperature of the water is increased. There is little other information about their behavior besides their mating pattern.

• Key Behaviors
• natatorial natatorial
• motile motile
• sedentary sedentary

Home Range

There is little known about the the territory sizes of individual plains topminnows. It is suspected that there are low amounts of intraspacific competition due to the low abundance of adults.

Communication and Perception

Plains topminnows are not schooling minnows like many others in the genus Fundulus . They perceive their environment using their eyes and lateral line. The lateral line in any fish runs along the middle of their body from the opercle to the beginning of the caudal fin. Its functions include water current sensation and vibration detection.

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

There have been no studies published on the feeding behavior of plains topminnows in the wild. Several papers have proposed that they are sustained by a diet of fly larvae ( Diptera ), specifically nonbiting midges ( Chironomidae ) and black flies ( Simuliidae ), plankton skimmed from the surface, crustaceans ( Crustacea ), and snails of the genus Physa . These assumptions are based on the habitat of the minnow and the morphology of the jaw, which is adapted for feeding at the surface of the water. In labs, plains topminnows are fed a diet of insects.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
  • eats non-insect arthropods
  • molluscivore molluscivore
• planktivore planktivore

• Animal Foods
• insects
• mollusks
• aquatic or marine worms
• aquatic crustaceans
• other marine invertebrates
• zooplankton zooplankton

Predation

There is only speculation in regards to predators of plains topminnows, due to lack of study. It is assumed that various species of pisciviorus fishes, green sunfish ( Lepomis cyanellus ), creek chubs ( Semotilus atromaculatus ), birds ( Aves ), and black bullheads ( Ameiurus melas ) are the main predators. These species live in the same habitat as plains topminnows and prey upon similar species.

Ecosystem Roles

Plains topminnows contribute to the foodweb as predators and prey, though their food habits and predators are not well understood. A fair amount of evidence suggests that populations of plains topminnows declined after the introduction of western mosquitofish ( Gambusia affinis ). Western mosquitofish, which have very similar habitat requirements, were introduced with the intent of reducing mosquito populations, motivated by fear of West Nile virus. In laboratory settings, extreme aggression by western mosquitofish is observed against plains topminnows.

Plains topminnows are host to two species-specific parasites. The flatworm Salsuginus yutanensis infects the gills, and is ingested as the minnow takes in oxygen. Plains topminnows are also affected by the trematode Phyllodistomium funduli , which infects the urinary blander and the ureters of the minnow. The Phyllodistomium funduli is suspected to be ingested by the eating of small clams, which are the intermediate host of this parasite. There is no evidence that either of these parasites kill their host.

Economic Importance for Humans: Positive

Plains topminnows are aquarium fish and bait fish. They make a very hardy addition to most aquariums, despite being a very aggressive fish that often attacks other fish. Plains topminnows are used quite often as a bait, though this not legal in all states due to their low numbers. For example, it is illegal to possess these minnows as bait fish in the state of Colorado.

• Positive Impacts
• pet trade pet trade
• food food

Economic Importance for Humans: Negative

Western mosquitofish ( Gambusia affinis ) have been introduced into several habitats of the plains topminnow as a way to help control mosquito populations and provide economic benefit to humans. Because plains topminnows compete heavily with western moquitofish, there is an indirect negative economic impact on humans.

Conservation Status

Plains topminnows are assumed to be stable across their home range. They are not considered a threatened, endangered or sensitive species by the federal government. They are considered rare in South Dakota, and a sensitive species within United States Forest Service Region 2. These statuses are a result of their limited habitat and slowly declining numbers. Declining numbers are a result of ditching, and draining for irrigation to be used to water crops, as well as the introduction of the western mosquitofish ( Gambusia affinis ). Some other ways that the habitat is being lost is through sedimentation from agricultural runoff, and pollutants being introduced into the habitat. A recent study in Nebraska showed that plains topminnows have disappeared from 75% of the 643 historic sites in Nebraska. Some conservation efforts exist. In 1994, the state government of Colorado attempted restoration efforts to the habitat of plains topminnows, reintroducing the species back into where it was thought to have been previously inhabited.

Other Comments

Plains topminnows suffers from severe habitat fragmentation, which causes a lot of diversity among this species. This makes gene flow impossible, and causes a large amount of genetic variation. A sample of this species showed a 61% variation among males and 83% variation among females. This variation has caused the species to be discovered several different times within a short period of time by accident. Despite the severe differences, this species lacks a subspecies designation due to extreme genetic homogeneity within and between populations, possibly a result of the bottleneck effect.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

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

References

Cope, 2009. "Fundulus sciadicus" (On-line). Natureserve Explorer. Accessed March 24, 2012 at http://www.natureserve.org/explorer/servlet/NatureServe?searchName=Fundulus%20sciadicus .

Ferdig, M., M. McDowell, J. Janovy, Jr.. 1991. SALSUGINUS YUTANENSIS N. SP. (MONOGENEA: ANCYROCEPHALIDAE) FROM FUNDULUS SCIADICUS IN CLEAR CREEK OF EASTERN NEBRASKA. American Society of Parasitologists , 77(1): 58-61. Accessed February 08, 2012 at http://www.jstor.org/stable/pdfplus/3282556.pdf?acceptTC=true .

Glaser, O. 1912. CHANGES IN CHEMICAL ENERGY DURING THE DEVELOPMENT OF FUNDULUS HETEROCLITUS. Science , 35/892: 189-191. Accessed February 08, 2012 at http://www.sciencemag.org/content/35/892/189.1.full.pdf?sid=b15e27d5-cd78-4751-ab8c-93281cca8845 .

Helt, J., J. Janovy, J. Ubelaker. 2003. Phyllodistomum funduli n. sp. (Trematoda: Gorgoderidae) from Fundulus sciadicus Cope from Cedar Creek in Western Nebraska. The Journal of Parasitology , 89(2): 346-350. Accessed February 08, 2012 at http://www.jstor.org/stable/pdfplus/3285959.pdf?acceptTC=true .

Kinney, T., J. Lynch. 1991. The fecundity and reproductive seasons of Fundulud sciadicus. Transactions of the Nebraska Academy of Sciences , XVIII: 104-104.

Koupal, K., C. Pasbrig. 2010. Development, Growth and Reproduction of Plains Topminnow, Fundulus sciadicus, in a Broodstock Pond Located at Sacramento-Wilcox Management Area. Project No. T-57: 1-20. Accessed March 22, 2012 at http://nlc1.nlc.state.ne.us/epubs/G1000/B145-2010.pdf .

Li, C., M. Bessert, G. Orti. 2009. Low Variation but strong population structure in mitochondrial control region of the plains top minnow, Fundulus sciadicus. Journal of Fish Biology , 74: 1037-1048. Accessed March 21, 2012 at http://golab.unl.edu/publications/Li_et_al_2009.pdf .

M.L., B., M. J., O. G.. 2009. Low variation but strong population structure in mitochondrial control regions of the plains topminnow, Fundulusus sciadicus. Journal of Fish Biology , 74: 1037-1048.

NEWMAN, H. 1909. THE QUESTION OF VIVIPARITY IN FUNDULUS MAJALIS. Science , VOL. XXX. No. 778: 769-771. Accessed February 08, 2012 at http://www.sciencemag.org/content/30/778/769.full.pdf?sid=b15e27d5-cd78-4751-ab8c-93281cca8845 .

O’Hare, J. 1985. Morphological and biochemical variation of disjunct populations of plains topminnow, Fundulus sciadicus . Omaha, NE: MSc Thesis, University of Nebraska.

Pflieger, W., P. Smith. 1997. The fishes of Missouri . Jefferson City: Missouri Dept. of Conservation.

Rahel, F., L. Thel. 2004. Plains Topminnow ( Fundulus sciadicus ): A Technical Conservation Assessment. USDA Forest Service, Roky Mountain Region, Species Conservation Project: 1-45. Accessed March 21, 2012 at http://www.fs.fed.us/r2/projects/scp/assessments/plainstopminnow.pdf .

SUMNER, F. 1911. FUNDULUS AND FRESH WATER. Science , VOL. XXXIV. No. 887: 928-931. Accessed February 08, 2012 at http://www.sciencemag.org/content/34/887/928.full.pdf?sid=b15e27d5-cd78-4751-ab8c-93281cca8845 .

Smith, E., N. Hoboken. 1912. Fundulus and fresh water. Science , XXXV No. 891: 144-145. Accessed March 20, 2012 at http://www.sciencemag.org/content/35/891/144.1.full.pdf .

Game and Parks Commission. Development, Growth and Reproduction of Plains Topminnow, Fundulus sciadicus , in a Broodstock Pond Located at Sacramento-Wilcox Management Area. T-57. Lincoln, NE 68508: Nebraska Publications Clearinghouse. 2010. Accessed March 19, 2012 at http://nlc1.nlc.state.ne.us/epubs/G1000/B145-2010.pdf .