NO. 3534 EURYTEMORA — WILSON AND TASH 567 



evidence for the bionomics of E. arctica, and only some speculative 

 points that might have value in future studies can be offered. Pre- 

 svmiably development in some pools is both earlier and more rapid 

 than in other pools and in Lake 4. The appearance of adults of E. 

 arctica in one pool and of E. gmcilicauda in two pools as early as June 

 29, 1960, cannot be accounted for by overwintering of live specimens, 

 because the pools are so shallow they would freeze to the bottom 

 before thawing. It is more reasonable to assume that the populations 

 of these two species developed from overwintering resting eggs in 

 bodies of water that not only melted early (as was observed in the 

 coastal area for some bodies of water in May) but had a high enough 

 temperature to permit a comparatively rapid development of some of 

 the population to the adult stage. If such bodies of water did not 

 dry out daring the summer season there would be time for develop- 

 ment of a second generation as Oloffson (1918) postulated for E. raboH 

 in Spitzbergen and as may be true for some Alaskan Eurytemora. On 

 the other hand, adults of a monocyclic population that developed 

 rapidly might not persist long after egg production in a shallow^ pool 

 with fluctuating water level where it is associated with a related and 

 more dominant species. Successful collection of a short-lived, mono- 

 cyclic species would be dependent upon an element of chance in 

 sampling the body of water at the particular short period of time when 

 identifiable copepodid stages were present. Such factors might ac- 

 count in part for failure to collect more specimens of E. arctica in the 

 coastal pools. An additional factor that might be very important but 

 difficult to assess until more of the numerous bodies of water along the 

 coast of Alaska are investigated, is that brackish water even of very 

 low salinity is a marginal habitat for E. arctica, it being dominantly 

 a freshwater species. 



Coastal Pools and Ponds 



Three species of Eurytemora were collected in pools and ponds on 

 the coast (table 1). Of these, precisely identifiable copepodid stages 

 of E. arctica occurred only as one or two specimens in four pools in 

 1960, so that its importance as part of the coastal brackish fauna is 

 not known. The other two species, E. canadensis and E. gracilicauda, 

 occurred in large numbers and frequently enough to be considered 

 characteristic elements of both fresh and brackish coastal bodies of 

 water. They were associated with one another in brackish pools or 

 occasionally with Limnocalanus johanseni, a dominant associate of 

 Eurytemora in nearby lagoons and the only other calanoid copepod 

 found in the brackish pools. In freshwater pools, E. gracilicauda 

 occurred with the freshwater calanoid Heterocope septentrionalis. 



