FIELD BOOK OF PONDS AND STREAMS 



every feature of a lamprey is peculiar. Its most striking one 

 is the large suction disk which surrounds the mouth, bearing 

 circlets of horny teeth upon its surface. The adult lamprey 

 fastens this armored oral disk to the side of a fish, rasps its 

 teeth into the flesh and sucks out the blood, and the fish 

 carries it about as long as it is able to swim (Fig. 270). 



Most species of lampreys pass part of their lives in salt 

 water but several kinds live entirely in fresh water and all of 

 them lay their eggs there. The lake lamprey or lamprey eel, 

 Petromyzon marinus, is one of those which lives in fresh water. 

 It is a land-locked form, generally considered the same species 

 as the great sea lamprey. Lampreys are abundant in the 

 Finger Lakes and tributary streams and in Oneida Lake alone 

 it is estimated that tons of fish are killed by them every year. 

 In spring these lampreys leave the lakes and migrate up the 

 creeks. They rest by night but travel by day until they final- 

 ly reach the riffly shallows where they make their nests. 

 There the male lamprey or a pair working together clears a sort 

 of shallow basin on the bottom, moving pebbles away from a 

 middle space and piling them in a low circular wall surround- 

 ing it. They pick up the stones with their oral disks, some- 

 times actually carrying them a foot or more. 



After the nest is completed the lampreys mate. They 

 cling to its upstream wall as if resting, but their rest is brief. 

 Using his oral sucker the male grasps the female behind her 

 head, twines his tail tightly against her sides, and for a short 

 period, generally only a few seconds, the two lampreys shake 

 and twist their bodies in great excitement. During this time 

 the eggs are laid and almost immediately buried beneath the 

 sand which is whirled over them by the struggling lampreys. 

 By the time the mating excitement is over the eggs are mostly 

 covered but as soon as they separate the two lampreys move 

 more sand and pebbles over them. They fan the sand with 

 their tails, the females having an extra growth of nn (anal) 

 at this time of year. They work at this for a few minutes, 



328 



