Animal Diversity Web

Ge­o­graphic Range

Slen­der mad­toms, No­tu­rus ex­ilis, occur within two dis­tinct ge­o­graphic areas within the Cen­tral High­lands of the United States. They are fairly un­com­monly found in the East­ern High­lands from cen­tral Ken­tucky south­ward to north­ern Al­abama within the drainages of the Green, Cum­ber­land and Ten­nessee Rivers. More com­monly, they are found in the In­te­rior High­lands from the upper and Cen­tral Mis­sis­sippi River basin in­clud­ing Mis­souri, Kansas, Ok­la­homa and Arkansas (where it is one of the most com­mon ben­thic fishes in Ozarkian streams), con­tin­u­ing spot­tily to the north as far as south­ern Min­nesota and Wis­con­sin. It has been pro­posed that this dis­junct range re­sulted from a Pleis­tocene vic­ari­ance which has been pre­served by the dis­per­sal bar­rier of low­land rivers that are slower and con­tain more sil­ta­tion than the streams the species typ­i­cally in­hab­its. (Et­nier and Starnes, 1993; Hardy, et al., 2002; Page and Burr, 1991; Phillips and Kil­ambi,, 1996)

• Biogeographic Regions
• nearctic
  • native

Habi­tat

Slen­der mad­toms in­habit clear streams with rocky or gravel bot­toms. Larger rocks are used for di­ur­nal hid­ing and gravel and rocks are re­quired for nest­ing. In Vives’ (1987) study, 79% of spec­i­mens were ac­quired in the vicin­ity of at least one siz­able rock that could pro­vide shel­ter. His re­search in­di­cates that the species prefers larger sub­strates in gen­eral. (Hardy, et al., 2002; Vives, 1987)

Vives (1987), in his analy­sis of north­east Ok­la­homa pop­u­la­tions, found the high­est fre­quency of N. ex­ilis in and above rif­fles, with very lit­tle use of aquatic veg­e­ta­tion. How­ever, he does not ad­dress mi­cro­hab­i­tat use by sea­son, which may show pat­terns sim­i­lar to other re­searchers. May­den and Burr (1981), who worked in south­ern Illi­nois, found the high­est fre­quency of adult spec­i­mens in pools ex­cept in June and July, when rif­fles are pre­ferred for nest build­ing and re­pro­duc­tion. Banks and Dis­te­fano (2002), work­ing in Mis­souri, found a trend to­ward uti­liza­tion of veg­e­tated patches and back­wa­ter pools in late sum­mer. This trend is pos­si­bly ex­plained by the use of the mi­cro­hab­i­tats as lo­ca­tions for nurs­ery areas, refuge from preda­tors, or sea­sonal abun­dance of in­ver­te­brate prey. (Banks and DiS­te­fano, 2002; May­den and Burr, 1981; Vives, 1987)

Vives (1987) col­lected spec­i­mens in var­i­ous cur­rent speeds, rang­ing from 8 to 98 cm/sec with a mean of 37.8 cm/sec and depths from 5 to 42 cm with mean of 18.2 cm (90% col­lected at less than 30 cm). Depth use was closely cor­re­lated with dis­tri­b­u­tion of dif­fer­ing depths avail­able. (Vives, 1987)

Banks and Dis­te­fano (2002), study­ing Mis­souri pop­u­la­tions, found con­trast­ing re­sults. N. ex­ilis in Mis­souri tends to be a habi­tat gen­er­al­ist, uti­liz­ing rif­fles, runs, deep pools, patches of emer­gent veg­e­ta­tion, and shal­low back­wa­ter pools dur­ing the day. Some mi­cro­hab­i­tat use may be linked to habi­tat par­ti­tion­ing with other species pre­sent in par­tic­u­lar streams. In Mis­souri, N. ex­ilis also seems to be a gen­er­al­ist re­gard­ing tol­er­ance of var­i­ous water depths and cur­rent ve­loc­i­ties. (Banks and DiS­te­fano, 2002)

• Habitat Regions
• temperate
• freshwater

• Aquatic Biomes
• benthic
• rivers and streams

• Range depth

  0.05 to 0.42 m

  0.16 to 1.38 ft

• Average depth

  0.182 m

  0.60 ft

Phys­i­cal De­scrip­tion

As in other mem­bers of the fam­ily Ic­taluri­dae, slen­der mad­toms ex­hibit eight con­spic­u­ous bar­bels around the mouth and have scale­less bod­ies. Slen­der mad­toms are named such due to their long, slen­der body, with pop­u­la­tions in cool clear habi­tats hav­ing even more slen­der form than those from warmer wa­ters. They have a flat­tened head with a ter­mi­nal mouth and jaws of equal pro­jec­tion. Their bod­ies are a con­tin­u­ous grey to dusky yel­low above with the ex­cep­tion of two light yel­low spots (a large spot on the nape, and a smaller one im­me­di­ately be­hind the dor­sal fin). Below, they are light yel­low to whitish. The dor­sal, anal and cau­dal fins are mostly pale with a black mar­gin which may or may not be com­plete, and is darker in cool, clear streams. The other fins are also pale, some­times yel­low­ish, with the pec­toral fins pos­sess­ing around six promi­nent ser­rae (teeth) along the rear edge. Meris­tics for the species are: 17 to 22 anal rays, 8 to 10 soft pec­toral fin rays and pelvic fin rays (usu­ally 9), 46 to 55 cau­dal fin rays, and 5 to 8 gill rak­ers. The fish reach a max­i­mum total length of about 15 cm, with most under 10 cm. (Et­nier and Starnes, 1993; Page and Burr, 1991)

Slen­der mad­toms are sim­i­lar to No­tu­rus flavus and No­tu­rus noc­tur­nus, which often ap­pear syn­topi­cally with N.​exilis, in shape and col­oration. How­ever both of these species lack well-de­vel­oped pec­toral spine teeth, and usu­ally do not ex­hibit a dark mar­ginal band on the dor­sal, anal and cau­dal fins. Ad­di­tion­ally, No­tu­rus in­sig­nis and N. ex­ilis are sim­i­lar in ap­pear­ance, and likely closely re­lated, but are found in dif­fer­ent streams. (Et­nier and Starnes, 1993)

A sep­a­rate race of N. ex­ilis may have formed in the White River of Arkansas and Mis­souri, ev­i­denced mor­pho­log­i­cally by a longer total length and more pig­men­ta­tion. (Burr, 1984; Burr, 1984; Burr, 1984)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry
• venomous

• Sexual Dimorphism
• male larger

• Range length

  <10 to 15 cm

  to 5.91 in

De­vel­op­ment

Fer­til­ized eggs range from 3.9 to 4.5 mm, with the great ma­jor­ity of the bulk being yolk. Hatch­ing oc­curs be­tween eight and nine days after fer­til­iza­tion, and hatch­lings are ac­tive and pos­sess rec­og­niz­able bar­bels and fins. By six days after hatch­ing, the lar­vae are re­mark­ably sim­i­lar in ap­pear­ance and be­hav­ior to adults and are about 11 to 12 mm total length. Black bands on anal, cau­dal and dor­sal fins ap­pear around day 32.

In­di­vid­u­als are one half the length of a one year old by three weeks. Sum­mer is the sea­son of great­est growth, par­tic­u­larly dur­ing the first two years of life, and in win­ter growth slows to a near stand­still. (May­den and Burr, 1981)

Re­pro­duc­tion

No sex­ual di­mor­phism re­lated to color pat­tern or fin size and shape ex­ists for slen­der mad­toms. Fe­males are typ­i­cally shorter than males, and weigh less per mm of stan­dard length. Dur­ing the breed­ing sea­son the males de­velop en­larged flat­tened heads with swollen lips as a means to guard nests. In fe­males and males alike the gen­i­tal papil­lae change, with the males’ be­com­ing swollen and more elon­gate and tis­sues sur­round­ing the fe­male papil­lae swelling. (Burr, 1984; May­den and Burr, 1981)

Male size cor­re­lates di­rectly to the num­ber of eggs in a nest. Fe­males typ­i­cally pro­duce twice as many ma­ture ova as are found in the av­er­age nest. It is there­fore likely that the species is polyan­drous, with fe­males lay­ing eggs in at least two males’ nests. (May­den and Burr, 1981)

• Mating System
• polyandrous

Late April to early June is the pe­riod of great­est re­pro­duc­tive fit­ness in north­east­ern Ok­la­homa pop­u­la­tions. How­ever, pro­tracted or mul­ti­ple spawn­ing through Au­gust may be pos­si­ble, in­di­cated by a spec­i­men col­lected in mid-Au­gust which con­tained over 50 ma­ture ova, ac­cord­ing to Vives (1987). In con­trast, May­den and Burr (1981) found that south­ern Illi­nois males ex­hibit breed­ing con­di­tion from April to Au­gust, and fe­males from April until late July, and sug­gest that that the breed­ing sea­son ends in July. Water tem­per­a­ture dur­ing breed­ing ranges from about 23.5 to 30 de­grees Cel­sius. (May­den and Burr, 1981)

Fe­males are ca­pa­ble of spawn­ing their first sum­mer, es­pe­cially in harsher north­ern con­di­tions, as long as a crit­i­cal size is at­tained (ap­prox­i­mately 50 mm in south­ern Illi­nois). In con­trast, males do not breed until two years of age. The ratio of ovary weight to ad­justed body weight (GSI) in­creased in fe­males in fall and spring, with greater rates of growth in ma­ture adults. (May­den and Burr, 1981)

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

• Breeding season

  April to late July spawning

• Range number of offspring

  26 to 124

• Range time to hatching

  8 to 9 days

• Average age at sexual or reproductive maturity (female)

  1 years

• Average age at sexual or reproductive maturity (male)

  2 years

Nests are ex­ca­vated by males early June, nearly al­ways un­der­neath large rocks with flat lower sides. The nests range in size from around 4 to 15 cm deep and 10 to 60 cm in width and are lined with fine silt-free gravel. Nests are spaced at least three to five me­ters apart. Eggs, in a sin­gle self-ad­he­sive clus­ter, are found in the deep­est part of the nest.

No­tu­rus ex­ilis fe­males likely exit the nest within 24 hours of spawn­ing and leave pro­tec­tion and care of the em­bryos to the male. Males guard the nests with­out feed­ing until the young be­come suf­fi­cient swim­mers. Scratches on the males’ flat­tened heads are a re­sult of con­fronta­tions while guard­ing nests. Dis­tur­bance and re­sult­ing ex­po­sure of the nest by re­searchers rarely scares away the de­ter­mined males.

In the White River, Mis­souri, nest guard­ing males were ap­prox­i­mately 100 mm in stan­dard length. As­so­ci­ated nests were lo­cated under rocks of ap­prox­i­mately 35 cm in length and width, in water ap­prox­i­mately 100 cm deep, in pools and race­ways. Nests con­tained from 26 to 124 em­bryos, whereas south­ern Illi­nois nests ranged from 27 to 74 eggs, with a mean of 51. (Burr, 1984; May­den and Burr, 1981)

• Parental Investment
• male parental care
• pre-hatching/birth
  • protecting
    • male
• pre-independence
  • protecting
    • male

Lifes­pan/Longevity

No­tu­rus ex­ilis of up to two to three years of age are not un­com­mon, and a few ex­cep­tional in­di­vid­u­als have been cap­tured that were four years or older.

Sur­vivor­ship may be most af­fected by sed­i­men­ta­tion re­lated to high water, and tem­per­a­ture shifts in ad­di­tion to bi­otic fac­tors. (Vives, 1987)

• Range lifespan
  Status: wild

  4 (high) years

• Typical lifespan
  Status: wild

  2 to 3 years

• Average lifespan
  Status: captivity

  4 years

  AnAge

Be­hav­ior

Adult slen­der mad­toms are weak dis­persers, with poor swim­ming abil­i­ties, a char­ac­ter­is­tic that may have con­tributed to the ex­is­tence of two dis­junct pop­u­la­tions of the species. (Hardy, et al., 2002)

• Key Behaviors
• natatorial
• nocturnal
• motile
• territorial

Com­mu­ni­ca­tion and Per­cep­tion

Mass con­gre­ga­tions of N. ex­ilis have been ob­served dur­ing spawn­ing sea­son, in­di­cat­ing that the species may share other cat­fishes’ use of scent to at­tract mates. (Vives, 1987)

• Communication Channels
• chemical

• Perception Channels
• tactile
• chemical

Food Habits

Slen­der mad­toms are noc­tur­nal feed­ers, with the great­est feed­ing ac­tiv­ity oc­cur­ring im­me­di­ately be­fore dawn. (May­den and Burr, 1981)

Analy­sis of the stom­ach con­tents of N. ex­ilis from North­west Arkansas streams has shown a diet con­sist­ing largely of in­sect lar­vae of the fam­ily Chi­rono­mi­dae in the win­ter and spring, and fam­i­lies Baeti­dae, Chi­rono­mi­dae and, to a lesser de­gree, Hep­ta­geni­idae dur­ing sum­mer and fall. The fluc­tu­a­tion in feed­ing is likely due to sea­sonal avail­abil­ity of prey items. Diet breadth seems to be re­stricted to only a few food types year round. (Phillips and Kil­ambi,, 1996)

North­east­ern Ok­la­homa pop­u­la­tions favor lar­vae of the order Ephemeroptera as well as chi­rono­mids (no sea­sonal data pro­vided). How­ever, they ex­hibit a greater breadth of food items, sug­gest­ing a more op­por­tunis­tic be­hav­ior than in north­west Arkansas pop­u­la­tions. (Vives, 1987)

South­ern Illi­nois pop­u­la­tions’ diet con­sist of all but 5% dipteran (Diptera), ephemeropteran and tri­chopteran (Tri­choptera) lar­vae and a few crus­taceans. Chi­rono­mids are the most fa­vored food source. Eggs of se­lect other species are also con­sumed. The least breadth of diet oc­currs in win­ter and the great­est in the spring. (May­den and Burr, 1981)

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

• Animal Foods
• insects
• aquatic or marine worms
• aquatic crustaceans

Pre­da­tion

Small­mouth bass (Mi­cropterus dolomieu) is a known preda­tor of N. ex­ilis, which may be one rea­son why N. ex­ilis prefers a noc­tur­nal lifestyle, seek­ing cover dur­ing the day when this vi­sual preda­tor is on the prowl. (Vives, 1987)

Em­bryo pre­da­tion by Or­conectes vir­ilis (vir­ile cray­fish), Cam­pos­toma anom­alum (cen­tral stoneroller) and Etheostoma caeruleum (rain­bow darter) has been noted. (May­den and Burr, 1981)

• Known Predators

  • Smallmouth bass (Micropterus dolomieu)
  • Virile crayfish (Orconectes virilis)
  • Central stoneroller (Campostoma anomalum)
  • Rainbow darter (Etheostoma caeruleum)

Ecosys­tem Roles

No­tu­rus ex­ilis is an in­sect preda­tor, a prey item for larger car­ni­vores, and fre­quently serves as a host to en­cysted nemo­todes (Nemo­toda), and, to a lesser de­gree, mem­bers of phy­lum Acan­tho­cephala. (May­den and Burr, 1981)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

No­tu­rus ex­ilis is not of eco­nomic im­por­tance since it is a rel­a­tively small, nongame fish that is rel­a­tively dif­fi­cult to col­lect.

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

No­tu­rus ex­ilis has one of the most painful stings from the ser­rae on the pec­toral spines of any of the cat­fishes. Ser­rae may in­flict wounds that can cause ex­treme swelling for sev­eral days. (Et­nier and Starnes, 1993; Et­nier and Starnes, 1993)

• Negative Impacts
• injures humans
  • bites or stings
  • venomous

Con­ser­va­tion Sta­tus

No­tu­rus ex­ilis has no spe­cial con­ser­va­tion sta­tus.

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Con­trib­u­tors

Amy McIn­tosh (au­thor), East­ern Ken­tucky Uni­ver­sity, Sherry Har­rel (ed­i­tor, in­struc­tor), East­ern Ken­tucky Uni­ver­sity, Mary Hejna (ed­i­tor), Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Banks, S., R. DiS­te­fano. 2002. Di­ur­nal Habi­tat As­so­ci­a­tions of the Mad­toms No­tu­rus al­bater, N. ex­ilis, N. flavater and N. flavus in Mis­souri Ozarks Streams. Amer­i­can Mid­land Nat­u­ral­ist, 148: 138-145.

Burr, B. 1984. Re­pro­duc­tive Bi­ol­ogy of the Check­ered Mad­tom (No­tu­rus flavater) with Ob­ser­va­tions on Nest­ing in the Ozark (N. al­bater) and Slen­der ( N. ex­ilis) Mad­toms (Sil­u­ri­formes: Ic­taluri­dae). Amer­i­can Mid­land Nat­u­ral­ist, 112: 408-414.

Et­nier, D., W. Starnes. 1993. The Fishes of Ten­nessee. Knoxville: Uni­ver­sity of Ten­nessee Press.

Hardy, M., J. Grady, E. Rout­man. 2002. In­traspe­cific phy­lo­geog­ra­phy of the slen­der mad­tom: the com­plex evo­lu­tion­ary his­tory of the Cen­tral High­lands of the United States. Mol­e­c­u­lar Ecol­ogy, 11: 2293-2403.

May­den, R., B. Burr. 1981. Life His­tory of the Slen­der Mad­tom, No­tu­rus ex­ilis, in South­ern Illi­nois (Pisces: Ic­taluri­dae).. Oc­ca­sional Pa­pers of the Mu­seum of Nat­ural His­tory: 1-64.

Page, L., B. Burr. 1991. A Field Guide to the Fresh­wa­ter Fishes: North Amer­ica North of Mex­ico. New York: Houghton Mif­flin Com­pany.

Phillips, E., R. Kil­ambi,. 1996. Food habits of four ben­thic fish species (Etheostoma spectabile, Percina caprodes, No­tu­rus ex­ilis, Cot­tus car­oli­nae) from north­west Arkansas streams. The South­west­ern Nat­u­ral­ist, 41: 69-73.

Vives, S. 1987. As­pects of the life his­tory of the slen­der mad­tom No­tu­rus ex­ilis in north­east­ern Ok­la­homa (Pisces: Ic­taluri­dae). Amer­i­can Mid­land Nat­u­ral­ist, 117: 167-176.