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Rhinichthys atratulus; Sexual dimorphism (Animals); Sexual behavior in animals; Mississippi River (Minn.)


Breeding activities and sexual dimorphism of the minnow Rhinichthys atratulus meleagris were studied in the headwaters of the Mississippi River at Minnesota's Itasca Stole Pork. The following characteristics were measured in 25 specimens of each sex: Total length, standard length, length of pectoral fins, length of pelvic fins, height of anal fin, length of caudal fin, fork length of caudal fin, length of depressed dorsal fin, and depth of caudal peduncle. The anal fin differed most significantly between the sexes, being long and keeled in females and comparatively truncated in males. Mating behavior was also observed. Results suggest that differences between sexes in general morphology and in breeding behavior may be related.

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