Doctoral Dissertations

Date of Award

8-1986

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

David A. Etnier

Committee Members

A. C. Echternacht, D. L. Bunting, P. W. Parmalee

Abstract

Intra- and interspecific variation of species of the subgenus Erimystax, genus Hybopsis, are analyzed using multivariate statistical techniques. Diagnoses, descriptions, figures, supporting tables, and distribution maps are provided to facilitate identification of the subgenus and component species. Results of multivariate analyses support the elevation of the Ozark subspecies of Hybopsis dissimilis to specific standing as Hybopsis i. insignis distributed in the lower Tennessee and Cumberland river drainages and H. insignis eristigma found in eastern tributaries of the upper Tennessee River drainage. Populations interpreted as intergrades occur in the Clinch, Powell, and Holston rivers. Two subspecies of Hybopsis x-punctata are recognized with H. x. x-punctata occurring in the upper Mississippi, Missouri, Neosho, and Ouachita river drainages and H. x-punctata trautmani inhabiting the Ohio, Thames, and White (Arkansas and Missouri) river drainages. Missouri River drainage populations are possible intergrades, pending further analysis. Two species groups are recognized within Erimystax. These are the dissimilus species group, composed of Hybopsis dissimilis, H. harryi, and H. insignis,and the x-punctata species group, composed of H. x-punctata and H. cahni.

Phylogenetic comparisons among the subgenus Erimystax, Hybopsis monacha, and subgenus Cyprinella of Notropis reveal H. monacha is an enigmatic species sharing characters with both subgenera. The exact phylogenetic placement of Hybopsis monacha is not known, but it is not considered a member of Erimystax.

Life history studies of Hybopsis x-punctata, H. harryi, H. dissimilis, and H. insignis were conducted and the findings are presented. Dietary analyses show H. harryi feeds primarily on periphytic detrital aggregate (PDA) and algae, whereas, the other species are more omnivorous and feed or relatively equal amounts of benthic invertebrates and PDA. Hybopsis harryi is the only Erimystax with a coiled gut configuration. The remaining species have a simple s-shape gut.

All species spawn over clean, gravel substrate during a three to four week period in April or May. Spawning may be initiated by a combination of rising water temperature and increased stream discharge. Males grow faster during the first 12 months of live but females are larger by the end of the second year. Females reach a larger maximum size and generally have higher survival rates than males. Maximum age recorded for each species is: Hybopsis harryi--42 months; H. x-punctata--32 months; H. insignis--30 months; and H. dissimilis--approximately 30 months.

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