CATFISH GENUS NOTURUS RAFINESQUE 27 



based on immature and adult stages. Ontogenetic change is minor and 

 has not complicated nomenclature in Noturus. 



Although Hubbs (1930, p. 432) had once recognized both Noturus 

 eleutherus and A^. furiosus from the Ohio Valley, these were later 

 regarded as conspecific, the result of sexual dimorphism (Hubbs and 

 Lagler, 1941, p. 65; Bailey and Taylor, 1950, p. 31). 



A re-examination has been made of all Ohio drainage and Great 

 Lakes material previously identified as Schilbeodes furiosus or Schil- 

 beodes eleutherus. Many collections from the Ohio Valley were found 

 to contain tAvo distinct morphological types. It was also noted that 

 samples from the Huron River, Michigan, consisted of only one of 

 the kinds, and collections from the upper Tennessee Valley, the other. 

 Examination of the gonads of these two forms indicated that each 

 contained both males and females, although one sex often predomi- 

 nated in a collection. Combination of several random samples of either 

 kind, however, suggested approximately a 50-50 ratio of males and 

 females in nature. Since no intermediates between the two forms 

 were present and since both males and females were represented in 

 each morphological type, the occurrence of two sympatric species in 

 the Ohio Valley is indicated. One of these, Noturus s^igrmosus (formerly 

 aligned with Schilbeodes furiosus), in contrast to the other, A^. eleu- 

 therus, is characterized by more caudal and anal rays, a longer and 

 more extensively serrated pectoral spine, a longer posterior process 

 of the cleithrum and dorsal spine, a deeper caudal peduncle, usually 

 by 11 preoperculomandibular pores (10 in eleutherus), and by several 

 distinctive features of pigmentation. The difference in number of 

 caudal rays in Ohio Valley specimens of the two species is indicated 

 in figure 4; no prominent sexual difference is apparent in either 

 species. 



In summary, external sexual differences, except perhaps in large 

 breeding ictalurids (which are not well known), are slight. They do 

 not constitute a complicating factor in the recognition of species. 

 Much of the confusion has arisen from lack of knowledge of changes 

 due to growth and sexual maturity. Plots of the number of serrae of 

 the pectoral spine in Noturus stigmosus (fig. 2) and in several other 

 species, suggest a slight sexual difference, the female perhaps averag- 

 ing more. No sexual difference in numbers of fin rays is evident (e.g., 

 figs. 1 and 4). 



Reproduction 



Little published observational work has been done on life histories 

 of the species of Noturus. Hankinson (1908) and R. M, Bailey (1938) 

 gave information on Noturus gyrinus; Fish (1932), Greeley (1929 

 and 1934), and Langlois (1954) recorded time of spawning, observa- 



298-943 0—69 S 



