FAMILY PETROMYZONIDAE 69 



of the Woods are of this species. They are very abundant in Lake of 

 the Woods. They are present in the Minnesota and St. Croix rivers 

 and probably in the other large streams and some lakes of Minnesota 

 and neighboring states. 



This lamprey is parasitic on fishes and is very destructive, espe- 

 cially in the Lake of the Woods region. When sexually mature the 

 adults ascend small streams to spawn, and die soon afterward. The 

 eggs develop into larval ammocoetes, which drift downstream into 

 quiet pools, where they spend a period of years developing in the 

 sand and mud. Eventually they metamorphose into parasitic adults 

 preying on fishes in large streams and lakes until they become sexually 

 mature. 



MICHIGAN BROOK LAMPREY 



Ichthyomyzon fossor Reighard and Cummins 



The body form of the Michigan brook lamprey is similar to that of 

 the silver lamprey except that the funnellike buccal cavity is much 

 smaller. The adults after metamorphosis have degenerate digestive 

 tracts and do not feed. Hence this species is nonparasitic, and Hubbs 

 and Trautman (1937) consider it a nonparasitic derivative of the 

 silver lamprey. Ichthyomyzon unicuspis. 



Ichthyomyzon fossor has been reported from the Lake Superior 

 drainage in Michigan, from New York State, and from Wisconsin, by 

 Hubbs and Trautman. It is reported as hving in small rivers and 

 creeks. No specimens have been reported from Minnesota waters, and 

 it may not occur in this state. Greene (1935) stated that this species 

 is definitely known from the Mississippi drainage in Wisconsin. 



The life history and habits of this species have been studied by 

 Okkelberg (1922) . The Michigan brook lamprey passes several years 

 in the ammocoetid stage before metamorphosing. The adults do not 

 feed but usually live for a period of four to eight months before 

 spawning and dying. 



CHESTNUT LAMPREY 



Ichthyomyzon castaneus Girard 



The chestnut lamprey is a small, slender, eellike animal, 8 to 16 

 inches long, with a large funnel-shaped buccal cavity which, when ex- 

 panded, is greater in diameter than the body. The circumoral teeth are 

 partly bicuspid. The dorsal and caudal fins are continuous. 



This species is distributed through the Upper Mississippi Valley 

 and has been reported in the Great Lakes and in the Hudson Bay 

 drainage. It is not common in Minnesota. Hubbs and Trautman 

 (1937) reported it as rare in Lake Pepin. Several of the lampreys in 



