Macrhybopsis hyostoma (Gilbert 1884)

Shoal Chub

Figs. 1 A, 2; Table 1

Nocomis hyostomus. — Gilbert 1884: 203 (original description; East Fork of White River, at Bedford, Lawrence County, Indiana). Böhlke 1953: 34 (types in Stanford University collection). Gilbert 1998: 93 –94 (in type catalogue of North American Cyprinidae; syntypes in USNM and CAS). Eschmeyer 1998: 754 (in world catalogue of fishes; location of types).

? Hybopsis montanus.— Meek 1885: 526 –527 (original description; “Upper Missouri River basin”; identification uncertain).

Hybopsis (Erinemus) hyostomus.— Jordan 1885: 29 (in list).

Hybopsis hyostomus. — Woolman 1892: 258, 284–285, 287 (Kentucky records). Meek 1895: 137 (Nebraska and Ohio records). Forbes & Richardson 1920: 163 (Illinois distribution).

Hybopsis aestivalis. — Branson 1963: 215 –217, 219 (olfactory apparatus morphology). Branson 1975: 109 –111, figs. 1–2 (olfactory lamellae formation). Clay 1975: 138 –139 (key; description; Kentucky distribution). Higgins 1977: 1 –43, fig. 4 (in part; geographic variation in morphology). Wallace 1980: 180 (in part; brief account; distribution map of M. aestivalis complex). Gammon et al. 1991: 145 (Sugar Creek, Indiana). Gammon & Gammon 1993: 77 (extirpated from Eel River, Indiana).

Hybopsis (Erimystax) hyostomus.— Jordan & Evermann 1896: 315 –316 (key; description; distribution).

Hybopsis hyostoma. — Evermann & Hildebrand 1916: 445 (Clinch and Tennessee rivers records). Evermann 1918: 321, 346, 367 (Kentucky and Tennessee records).

Extrarius hyostomus. — Hubbs & Ortenburger 1929: 23 (included in Extrarius).

Macrhybopsis aestivalis. — Jordan et al. 1930: 138 (in part; list). Coburn & Cavender 1986: 1 (in part; phylogeny; included in Macrhybopsis). Robins et al. 1991: 21, 76 (in part; in list). Coburn & Cavender 1992: 332 (in part; phylogeny of cyprinid genera). Mayden et al. 1992: 836 (in part; in list of North American fishes). Dimmick 1993: 174, 176, 178, 181–182 (phylogeny of barbeled cyprinids). Etnier & Starnes 1994: 20, 192–194 (in part; description; Tennessee localities mapped; morphological variation). Stauffer et al. 1995: 15, 55, 102–103 (general account; key; West Virginia distribution mapped). Mettee et al. 1996: 218 –219 (in part; general account; photograph [upper figure only]; Alabama localities mapped).

Extrarius aestivalis. — Gerking 1945: 51 (general account; Indiana distribution mapped). Dimmick 1988: 73, 75, 78, fig. 2a (ultrastructure of barbels). Mayden 1989: 14 –15, fig. 9h (in part; phylogeny; Extrarius elevated to genus). Carney et al. 1992: 205 –206 (Tippecanoe River, Indiana). Page & Burr 1991: 106, pl. 9, map 118 (in part; description; distribution).

Extrarius aestivalis hyostomus.— Gerking 1945: 51 (distribution in Indiana).

Hybopsis aestivalis hyostoma. — Trautman 1957: 87, 310–311 (key; general account; Ohio distribution; status). Davis & Miller 1967: 7, 10, 14, 16–18, fig. 13 (brain morphology). Douglas 1974: 100 (subspecies in Louisiana). Clay 1975: 139 (subspecies in Kentucky). Higgins 1977: 13 –14, 42, figs. 5–7 (geographic variation in morphology). Trautman 1981: 93, 288–290, fig. 47 (key; general account; Ohio distribution; status). Wallace 1980: 180 (list of subspecies). Burr & Warren 1986: 371 (brief account; subspecies in Kentucky; Kentucky distribution mapped).

Hybopsis (Extrarius) aestivalis. — Davis & Miller 1967: 4 –9, 15–18, 32–36 (in part; brain morphology). Reno 1969: 738, 740– 743, 746–748, 753, 762–763, 765–766, 770; figs. 2, 26 (in part; variation and morphology of sensory pore system). Jenkins & Lachner 1971: 4, 6–9, 12 (scale morphology; vertebral counts). Burr & Warren 1986: 89, 371 (in part; habitat; Kentucky distribution mapped).

Macrhybopsis aestivalis hyostomus. — Etnier & Starnes 1994: 193 (subspecies in Tennessee and Cumberland rivers).

Macrhybopsis aestivalis hyostoma.— Boschung & Mayden 2004: 108 –109, pl. 20D (general account; illustration; distribution in Alabama).

Macrhybopsis hyostoma. — Nelson et al. 2004: 73 (in part; in North American fish checklist; elevated to species). Page et al. 2013: 73 (in part; in North American checklist).

The above literature citations, other than Hybopsis montanus, are limited to eastern populations of Macrhybopsis hyostoma from within the area of geographical coverage defined in the present paper.

Despite its broad geographic range and demonstrated morphological variability, the nomenclature of Macrhybopsis hyostoma, as presently recognized, has remained remarkably stable, with no junior synonyms as yet having been identified (Gilbert 1998: 28).

A list of non-type material examined during the present study, comprising 43 lots and 409 total specimens, appears in Appendix 1.

Status of Hybopsis montanus. The identity of Hybopsis montanus is uncertain (Gilbert 1998: 116; Eisenhour 2004: 31). Meek (1885: 526–527) indicated the description to have been based on three specimens, supposedly from the “upper Missouri River basin,” having 4-4 pharyngeal teeth (slightly hooked), a pair of well developed maxillary barbels, 37 lateral-line scales, 14 predorsal scales, and six anal rays (last character obviously erroneous), a slender and elongated body, body silvery (without spots), and dorsal fin situated directly above pelvic fins. Other than anal-ray count and lack of spots on the body, this is an accurate description of most populations of Macrhybopsis hyostoma, which does not occur in the upper Missouri River basin or any closely adjacent area (Wallace 1980: 180). The three specimens now in the type jar (USNM 36882) all have 1,4-4,1 pharyngeal teeth and are clearly identifiable as Notropis dorsalis (Gilbert 1998: 116; Eisenhour 2004: 31), a species absent from the upper Missouri basin (Gilbert & Burgess 1980a: 260). A substitution of specimens has obviously occurred at some time in the past, and the precise status of Hybopsis montanus will remain a mystery.

Syntypes. A total of 40 syntypes of Nocomis hyostomus were identified by Gilbert (1998: 93–94) and Eisenhour (2004: 31). All were collected at the type locality (White River, near Bedford, Lawrence County, Indiana) and are included in the following three museum lots (measurements in standard length): USNM 34980 (6, 44.0–47.4), CAS-SU 888 (30, 40.7–49.9) and CAS 58626 (4, 40.1–45.3). Böhlke (1953: 34) erroneously listed USNM 34980 as the “holotype”

Table]. Variation of selecteđ meristic characters in eastern species of Macrhybopsis. Incom. refers to number of incomplete scale rows.

Total body circumferential scales (including lateral-line scales) Predorsal scales

Incom. 20 21 22 23 24 25 26 27 28 No. Mean̲̲ 14 15 16 17 18 19 20 No. Mean Macrhybopsis hyostoma 1 4 1 2 7 2 6 2 1 8 1 5 6 2 5.3 9 1 4 21 23 20 5 2 85 15.85 Macrhybopsis boschungi 7 3 4 3 3 1 1 1 2 6.0 9 3 1 3 3 2 1 6 1 6 4 8 4 16.49 Macrhybopsis tomellerii 8 3 ---- ------ 1 1 2 3 3 2 7 8 2 8 3 1 7.4 2 Macrhybopsis etnieri 1 1 1 2 1 7 1 9 1 5 1 5 6 1 8 7 2 3.2 6 4 1 7 2 9 2 1 9 2 87 16.24 Macrhybopsis pallida 75 4 4 8 24.50 4 14 23 21 16 5 83 16.55

Pectoral-fin rays (both sides combined) Pelvic-fin rays (both sides combined) 12 13 14 15 16 17 No. Mean 7 8 9 No. Mean

Macrhybopsis hyostoma 1 1 8 1 1 4 3 7 170 15.70 3 163 166 7.98

Macrhybopsis boschungi 1 5 1 1 8 2 5 158 15.06 1 157 158 7.99

Macrhybopsis tomellerii 16 97 52 1 166 15.23 7 159 166 7.96

Macrhybopsis etnieri 1 21 84 46 152 14.15 7 162 1 170 7.96

Macrhybopsis pallida 27 80 53 4 164 14.24 1 167 168 7.99

Anal-fin rays Dorsal-fin rays Total Vertebrae

6 7 8 9 No. Mean 7 8 No. Mean 34 35 36 37 38 39 No. Mean Macrhybopsis hyostoma 4 106 6 116 8.02 8 5 8 5 8.0 0 8 4 0 2 7 2 7 7 3 7.3 0 Macrhybopsis boschungi 6 142 148 7.96 8 9 5 9 8.0 0 1 9 7 9 1 4 103 36.03 Macrhybopsis tomellerii 10 114 1 125 7.93 9 0 9 0 8.0 0 1 2 6 5 5 1 7 9 9 3 5.8 9 Macrhybopsis etnieri 8 182 190 7.96 1 104 105 7.99 23 121 40 184 38.09 Macrhybopsis pallida 2 171 2 175 7.00 8 4 8 4 8.0 0 1 0 5 3 1 3 7 6 36.04

Pharyngeal teeth 4-4 0,4-4,1 1,4-4,0 1,4-4,1

Macrhybopsis hyostoma 25

Macrhybopsis boschungi 28

Machybopsis tomellerii 25

Macrhybopsis etnieri 2 5 8 5 6 Macrhybopsis pallida 2 5

Diagnosis. The following diagnosis is based solely on populations occurring east of the Mississippi River (comprising a total of 43 lots and 409 specimens), the geographic limits of which extend from the Tennessee River drainage north to the Ohio River drainage (Fig. 2, Appendix 1). Those from the Ohio River drainage include material from the states of West Virginia, Kentucky, Ohio and Indiana west to the Wabash River system, which (in its lower reaches) forms the boundary between Indiana and Illinois. An expanded diagnosis of Macrhybopsis hyostoma appears in Eisenhour’s (2004: 31–34) study, which is largely confined to populations west of the Mississippi River.

A member of the Macrhybopsis aestivalis complex, as defined in the generic diagnosis. Characterized by a single pair of moderately long maxillary barbels, 4-4 pharyngeal teeth, eight anal rays, anal opening closer to analfin origin than pelvic-fin origin (ca. 70 percent of intervening distance), and prominent dark melanophores on upper two-thirds of body (Fig. 1 A) (also see Smith 1979: 75; Trautman 1981: fig. 47; Boschung & Mayden 2004: pl. 20D). Among other eastern species of the complex, the first four characters are shared with M. boschungi and M. tomellerii, which differ most notably in having the body melanophores much reduced in size (Figs. 1 B, 1E). Other important diagnostic characters for M. hyostoma include a complete bridge of scales across belly (two to five scale rows deep), the bridge incomplete or absent in about 20 percent of specimens examined; genital papillae extremely reduced; dorsal-fin origin situated very slightly posterior to imaginary line extending upward from pelvic fin origins; and pectoral fins in both sexes relatively short, rounded to bluntly pointed, never sharply pointed in adult males.

The two remaining eastern members of the complex (M. etnieri and M. pallida) differ from M. hyostoma in having the anal opening located midway between the origins of the pelvic and anal fins. Additional diagnostic differences include 1,4-4,1 pharyngeal teeth in M. etnieri and a combination of two pairs of maxillary barbels and seven anal rays in M. pallida.

Description. Characters listed in the diagnosis are not repeated here, unless additional clarification is required. Variation in meristic characters is presented in Table 1.

Dorsal-fin rays 8; anal-fin rays usually 8 (range 7–9); pectoral-fin rays usually 15 (range 14–16); pelvic-fin rays usually 8 (occasionally 7); lateral-line scales modally 37 (range 35–39); predorsal scales irregularly distributed and poorly defined, numbering 15–17 (range 14–19); body-circumferential scale rows above and between lateral lines usually 11 (range 9–12); body-circumferential scale rows below and between lateral lines usually 12–13 (range 11–14), the scales occasionally incomplete or absent from middle of belly; total caudalpeduncle scale rows uniformly 12 (five scale rows above and below lateral lines on each side of caudal peduncle); total vertebrae 37–38 (range 36–39); scales present and well developed in area between pelvic and anal fins; anal and dorsal fins usually angular and slightly falcate, the anteriormost rays (when depressed) extending about same distance posteriorly as posteriormost rays; head somewhat rounded and moderately flattened ventrally; mouth inferior and horizontal, not as wide as head; lips moderately fleshy, not thickened posteriorly; eyes oval in shape and relatively large, the diameter less than snout length; snout moderately long, blunt and rounded, its length more than length of orbit; genital papillae poorly developed as small conical or cylindrical extensions in both sexes; four or five rudimentary gill rakers on upper limb of outer (anteriormost) gill arch, these usually absent from lower limb but with four or five tiny gill rakers occasionally present; pharyngeal teeth short, thin, and hooked, with little or no grinding surface; nuptial tubercles present in membrane immediately posterior to first pectoral-fin ray; pectoral-fin rays 2–10 thickened in nuptial males and containing large, conical, recurved uniserial tubercles; tiny tubercles sometimes present on anteriormost rays of dorsal and pelvic fins in nuptial males.

Specimens in life without chromatic pigmentation; translucent pale green or gray on upper two-thirds of body, silvery white on lower third of body, including belly; predorsal stripe and postdorsal stripe usually absent, but occasionally present as a thin faint line; scales on upper side of body occasionally margined with a thin line of pigment; pigment on scales on upper two-thirds of body either evenly distributed over scale or slightly more concentrated on posterior half of scale; tiny melanophores on body often most densely concentrated along mid-side of body, where they may form a faint lateral stripe that is particularly prominent on posterior third of body.

Females attain a larger size than males, the largest female examined 61.3 mm SL (UT 55.1511) from Barren River, Warren County, Kentucky; the largest male recorded 53.6 mm SL (SIUC 7317) from Green River, Hart County, Kentucky (Eisenhour 1997).

Comments. As presently conceived, Macrhybopsis hyostoma is the most wide-ranging and morphologically variable member of the M. aestivalis complex. Based partly on its broad and centralized distribution, Eisenhour (1997) presumed M. hyostoma to be the group’s ancestral species. This situation remains complex and uncertain, however, and additional genetic study is required.

Among other eastern species, it most closely resembles Macrhybopsis boschungi and M. tomellerii, with which it shares a number of meristic and morphometric characters listed in the preceding diagnosis. However, genetic data, as discussed elsewhere in this paper, do not indicate an intimate relationship with either of those species.

Distribution. Macrhybopsis hyostoma is distributed, east of the Mississippi River, from the Tennessee River drainage of Alabama north to the Ohio River drainage in Illinois east to West Virginia (Fig. 2). The distribution of populations currently referred to this species from the Mississippi River westward are discussed elsewhere in this paper.

Habitat. Eastern populations of Macrhybopsis hyostoma inhabit large rivers and lowermost sections of the their major tributaries, in areas ranging from turbid to relatively clear water, a moderate to strong current, and a bottom of sand and gravel.

Etymology. The species name hyostoma is derived from the words hyo (=hog) and stoma (=mouth), in reference to the underlying position of the mouth relative to the projecting snout.