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Becker, George C. / Fishes of Wisconsin
(1983)

Lamprey family - petromyzontidae,   pp. 199-218 PDF (10.2 MB)


Page 199

 
Lamprey Family- 
            Petromyzontidae 
  Five species of lampreys in three genera are known from Wisconsin. 
Of these, three are parasitic and two nonparasitic. In the United States
and Canada, 17 species occur in 3 genera (Robins et al. 1980), and 13 of
the species are strictly freshwater forms. A fossil specimen of Mayomy- 
zon piekoensis was reported from the middle Pennsylvanian Francis Creek 
Shale of northeastern Illinois (Bardack and Zangerl 1968). 
  Lampreys are scaleless and cartilaginous with funnel-like mouths, 
often armed with horny teeth. A single, median nostril occurs anterior to
the eyes. Seven pairs of gills open to the outside, each by an individual
opening. A long single or double dorsal fin is continuous with the caudal
fin; paired fins are absent. 
  All adult lampreys show the following traits: (1) In breeding females 
the anal fin fold is well developed and the tail turns upward, while in the
males the anal fin fold is scarcely developed and the tail bends down- 
ward. (2) The lumen of the intestinal tract becomes nonfunctional and 
closes in fully mature individuals. (3) Between the time of peak physical
development and spawning, the lengths and weights of adult lampreys 
of both sexes diminish. At spawning time sexually mature individuals 
are much smaller than they were a few months previously (Vladykov 
1951). 
  Adults deposit their eggs in riffles of freshwater streams and then die.
Upon hatching, the larval young burrow into silt and sand in quiet water
where they filter-feed and grow. After 3 or more years, they metamor- 
phose into adults during late summer and early fall. The nonparasitic 
forms spawn the following spring but the parasitic lampreys not until a 
199 


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