Least Brook Lamprey in Kentucky 87 



Taxonomic Status of lethenteron meridionale 



Vladykov et al. (1975) described Lethenteron meridionale as a new 

 nonparasitic lamprey from Tennessee, Alabama and Georgia. In all 

 characters except dentition it is inseparable from L. aepyptera, despite 

 the fact that the authors concluded that it was a close relative of Lethen- 

 teron lamottenii (now Lampetra appendix; fide Bailey and Rohde in 

 Robins et al. 1980). As defined by Valdykov and his associates, mem- 

 bers of the genus Lethenteron always possess posterior circumoral teeth 

 and, partly because L. meridionale has posterior circumoral teeth, it was 

 accordingly assigned to the genus. However, Lampetra zanandreai, 

 which has been variously assigned to Lethenteron or Lampetra, occa- 

 sionally lacks posterior circumorals (Zanandrea 1957; Hubbs and Potter 

 1971). 



We found small, unicuspid posterior circumoral disc teeth in spec- 

 imens of L. aepyptera from several drainages throughout Kentucky. The 

 mean number of posterior circumorals in specimens having them was 

 7.6 (R = 1 - 22, N = 15). In most, these teeth formed an incomplete row 

 (Fig. 2), but in two individuals there was a complete infraoral row 

 extending between the two posterior inner laterals. In another specimen 

 there were several small, degenerate teeth scattered throughout the pos- 

 terior field of the disc. Several collections have specimens with and 

 without posterior circumorals. 



Fig. 2. Diagrammatic illustration of the oral disc of Lampetra aepyptera, show- 

 ing incomplete row of posterior circumoral teeth. Drawn from a composite of 

 several specimens. 



We noted variation in several other disc characters used in the 

 diagnosis of L. meridionale. The following counts are means based on 

 17 specimens of L aepyptera: oral papillae 16.3 (R = 12 - 20); infraoral 

 cusps 9.8 (R = 5 - 13); intermediate teeth in anterior field 14.3 (R = - 32); 

 inner lateral teeth 6.2 (R = 4 - 9). The counts for each of these characters 

 as reported by Vladykov et al. overlap between L. aepyptera and L. 



