Family PETROMYZONIDAE 



THE LAMPREY FAMILY 



The lampreys, or lamper eels, are characterized by the circular fun- 

 nellike "mouth," or buccal cavity, armed with toothlike horny spines. 

 They are without scales or paired fins and possess but a single nostril. 

 The skeleton is wholly of cartilage and consists of an imperfect skull 

 and a poorly developed vertebral column supported by an uncon- 

 stricted notochord. Seven pairs of external gill-openings are present. 

 The gills are supported by an arrangement of cartilage known as the 

 branchial basket. 



The buccal cavity, or buccal funnel, contains horny, toothlike spines; 

 those immediately surrounding the mouth opening are commonly called 

 the circumoral teeth. Bordering the opening of the mouth anteriorly 

 and posteriorly are horny plates bearing spines known as the swpraoral 

 and infraoral laminae. The transverse lingual lamina and the longitudi- 

 nal lingual laminae are the teeth of the tongue. 



The lampreys of the central United States have nonparasitic larval 

 stages called ammocoetes. These larvae are blind, eeUike forms living 

 a more or less sedentary life buried in the mud. In this manner they 

 spend a period of years, eventually metamorphosing into active adults. 

 At the end of the larval period the ammocoetes may be larger than 

 the adults. Ammocoetes have been reported by Creaser and Hann 

 (1929) as feeding largely on algae. 



The species of lampreys native to Minnesota and its neighboring 

 states are all small. A marine species, the river, or great sea, lamprey, 

 Petromyzon marinus Linnaeus, found on the Atlantic Coast, reaches a 

 length of over 2 feet. This species ordinarily ascends rivers to spawn 

 and has become landlocked in certain eastern lakes. It has recently 

 invaded the Great Lakes by way of the Welland Canal, and has 

 caused considerable damage to commercial fishes. It has been reported 

 at the eastern end of Lake Superior and will probably appear off the 

 Minnesota North Shore within a few years. 



The classification of the fresh-water lampreys has been revised by 

 Hubbs and Trautman (1937) , and four species are assigned as native 

 to the Minnesota region. Three of these species belong to the genus 

 Ichthyomyzon, and one species belongs to the genus Entosphenu^, 

 formerly called Lampetra. 



Key to Common Species of Family PETROMYZONIDAE 



1 . Dorsal fin continuous, not divided 2 



Dorsal fin distinctly divided; digestive tract rudimentary in adult 



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