Characteristics of an Intergeneric Cyprinid Hybrid, Campostoma anomalum x Luxilus sp. Indet. (Pisces: Cyprinidae), from the Portage River, Ohio

Characteristics of a hybrid, Campostoma anomalum pullum x Luxilus sp. (chrysocephalus, comutus, their hybrid, or a backcross) from the Portage River, OH, were examined and compared with parental species as well as five other Campostoma anomalum x Luxilus cornutus and C. anomalum x L. chrysocephalus hybrids from Ohio, Tennessee, New York, Virginia, and Mississippi. Lateral-line scale count and gill raker count were consistently intermediate in all hybrids. Dentition was intermediate in four of five hybrids, and intestinal diameter was intermediate in both Ohio hybrids. Hybrids for which data were available (n = 5) resembled Luxilus in lacking intestinal coiling around the swimbladder and in liver shape and position (n = 4). Mouth position was intermediate in five of six hybrids. The Portage River hybrid may be a tri-hybrid based on apparent hybridization between the two Luxilus species, L. cornutus andZ. chrysocephalus, present at the collection site. OHIO J. SCI. 97 (3): 40-43, 1997 INTRODUCTION Many natural hybrid combinations among cyprinids have been documented (Schwartz 1972, 1981). Cyprinid hybrids often result from accidental mixing of gametes during spawning due to nest "sharing" by several species. Species of non-nest building cyprinids often spawn over the nests of Nocomis, Campostoma, Exoglossum, or Semotilus (Raney 1940, 1947), and Thoma and Rankin (1988) found the incidence of Luxilus chrysocephalus (striped shiner) x Notropis rubellus (rosyface shiner) hybrids in Ohio streams strongly correlated with the presence of either Nocomis biguttatus (hornyhead chub) or N. micropogon (river chub). Trautman (1981) recorded the hybrid combinations Campostoma anomalum (stoneroller) x L. cornutus (common shiner) and C. anomalum x L. chrysocephalus from Ohio; however, character descriptions were not provided for these hybrids. Characters of a C. a. pullum x L. cornutus (UMMZ 121844) collected in Lost Creek, Defiance County, OH on 30 May 1938 by M. B. Trautman and G. A. Moore were examined and included herein. Menzel (1978) analyzed characters of a C. a. pullum x L. cornutus (CU 64399) from Sixmile Creek, Tompkins County, NY, and Grady and Cashner (1988) described the characteristics of a C. a. pullum x L. chrysocephalus isolepis (UNOVC 5336) from Clark Creek, Wilkinson County, MS. A hybrid Campostoma anomalum pullum x Luxilus chrysocephalus/cornutus was captured 13 July 1994 in the Portage River (PR), Lake Erie Drainage, at Pemberville, OH (Freedom Township, Wood County) by Ohio Environmental Protection Agency (OEPA) personnel (R. J. Miltner, K. M. Capuzzi, and W. J. Poly). The hybrid specimen (UT 44.6648) was preserved along with a series of each suspected parental species (UT 44.6646, UT 44.6647). The site was seined by the author on 23 May 1995 in search of more hybrids; however, none were 'Manuscript received 10 November 1995 and in revised form 2 August 1996 (#95-20). captured. Also, two specimens of C. a. anomalum x Z. chrysocephalus from Bletcher's Creek, Anderson County, TN and Bear Creek, Smyth County, VA (UT 44.3017 and UT 44.5785, respectively) were collected (D. A. Etnier, Univ. Tenn. pers. comm.) and included in the present study. Hybrids often exhibit a combination of intermediacy and mosaic parental traits (Menzel 1978, Greenfield et al. 1973, Grady and Cashner 1988). Because the range of character variation in intergeneric hybrids can be even more extreme than the ranges of both parental species combined (Hubbs and Strawn 1957, Retzer and Walsh 1982, Grady and Cashner 1988), the characteristics of one hybrid specimen are not necessarily representative of even a typical hybrid of any given hybrid combination. In order to contribute additional information on natural hybrids, I compared characteristics of six C. anomalum x L. spp. with putative parental taxa. MATERIALS AND METHODS Twelve meristic, eleven morphometric (ten external, one internal), and several qualitative characters were examined and compared among the hybrids and parental species (n = 11 C. a. pullum and Luxilus sp. from the Portage River taken with hybrid on 13 July 1994). Data for the New York and Mississippi hybrids were taken from Menzel (1978) and Grady and Cashner (1988), respectively. Counts and measurements follow Hubbs and Lagler (1958). External measurements were made to the nearest mm with dividers. Morphometrics are expressed as percentage of standard length or head length. Intestine diameter was measured to the nearest 0.1 mm with dial calipers (mean of three measurements per fish). Chin pigmentation and anterior dorso-lateral scale counts (fifth scale row above lateral line) follow Gilbert (1964). Head length excluded the opercular membrane. Lateral scale size and shape were determined from scales taken one scale row above the lateral line below the dorsal fin insertion. Jaw osteology and vertebrae were visualized OHIO JOURNAL OF SCIENCE W. J. POLY 41 with the use of soft x-rays (3A, 30 mv, 15 sec). Data for each character were compared qualitatively among the hybrids and parental taxa. The following abbreviations are used in the text and Table 1: anterior dorso-lateral scales (ADLS), circumferential scales (CS), lateral line (LL), lateral-line scales (LLS), chin pigmentation (CP), back