EMBRYOLOGICAL STAGES IN THE SEA LAMPREY AND EFFECTS 

 OF TEMPERATURE ON DEVELOPMENT 



By George W. Piavis, Fishery Research Biologist 



The Great Lakes fisheries, the Nation's 

 richest source of fresh-water fishes for both com- 

 mercial and recreational fishing, have suffered 

 depletion of catch and the threat of disaster. 

 The danger has its origin in an increase in abund- 

 ance of the sea lampre\-, Petromyzon marinv^, 

 which is parisitic on and highly destructive of 

 fish. Major goals of the Great Lakes research 

 program of the U.S. Fish and Wildlife Service have 

 been to develop techniques for controlling this 

 menace, to restore the Great Lakes fishery stocks 

 to an economically profitable level of abundance, 

 and to sustain them at that level. 



Others have outlined in detail the history' of the 

 sea lamprey within the St. Lawrence drainage and 

 their invasion of tlie upper Great Lakes: (Gage, 

 1928; Creaser, 1932; Hubbs and Pope, 1937; 

 Applegate and Moffett, 1955). The sequence of 

 this invasion was summarized by Applegate (1950) 

 as follows: 1921, Lake Erie; 1934, Lake St. Clair; 

 1936, Lake Huron; 1937, Lake Michigan; 1946, 

 Lake Superior. 



In planning an attack against the ever-increas- 

 ing numbers of sea lampreys, practically every 

 phase of their life history has been investigated 

 except that of early embryology. A search of the 

 literature reveals little on the embryology of 

 P. rnarinu-s, Lampetra flumatilis, L. planeri, and 

 Ichthyomyzon unicmipis, the significant predators. 

 Still less has been written concerning the other 

 lampreys. Clear-cut stage designations are lack- 

 ing for all lampre3's. The usual embryological 

 designations for the common early stages of 

 development are mentioned through the gastrula 

 stage, but even tliese lack clear definition. 



In order to portra}' accurateh' the embryology 

 of P. marinus, a study was undertaken which had 

 as its objective the determination and definition 

 of the various stages of development. 



XoiE.— Dr. Plavls Is presently Assistant Prolessor of Anatomy, Balti- 

 more College of Dental Surgery, Dental School. University of Maryland, 

 Baltimore I, Md. 



Fishery Bulletin 1S2. Approved for publication May 4, I96U. 



In these studies, staging of lamprey development 

 has been considered essential to a better under- 

 standing of the results of the series of experiments 

 on effects of temperature. It was immediately 

 obvious that differences in developmental time 

 periods would result from variations in tempera- 

 tures. In order to place the entire series of temp- 

 erature experiments on a common basis, an accur- 

 ate series of stages was of the utmost importance. 



A second objective of this study was to deter- 

 mine the range of temperature for development of 

 P. marinus eggs as well as their optimum develop- 

 mental temperature. 



This work began with a preliminary investiga- 

 tion conducted on a part-time basis during the 

 summer of 1954. Intensive investigations were 

 carried on throughout the spring and summer of 

 1955 when temperature experiments were under- 

 taken. Confirmatory temperature experiments at 

 65° F. (18.4° C.) were conducted in the summer of 

 1956. These latter experiments also provided 

 materials for normal staging. 



This research was conducted as part of my 

 graduate training at Duke University while 

 employed at Hammond Bay as a fishery research 

 biologist b}- the Great Lakes Biological Laboratory 

 of the U.S. Fish and Wildlife Service. 



Embryological studies and experimental work 

 on living materials were conducted at Hammond 

 Ba3' where the facilities of the sea lamprey research 

 laboratory were placed at my disposal by Dr. 

 James W. Moffett, Director of the Bureau's 

 Great Lakes Biological Laboratories, and Dr. 

 Vernon C. Applegate, Chief of the Hammond Bay 

 Laboratory. Sectioning and statistical work were 

 conducted at Duke University. The University 

 also provided me with a refrigeration unit for use 

 at Hammond Bay and the other facilities and 

 materials necessary to the investigation. 



Dr. Edward C. Horn, Duke University, knows 

 of my appreciation for his many criticisms and 

 patient guidance. I wish also to thank the staff 



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