NO. 3534 EURYTEMORA — WILSON AND TASH 565 



Arctic Slope species that range from brackish into fresh water were 

 collected in them. As presently known the species occurs commonly 

 in small, shallow freshwater tundra lakes, pools, and ponds, and 

 rarely in coastal brackish pools. Its distributional range is in the 

 Arctic Slope and Brooks Range physiographic provinces, from the 

 coastal region of Cape Thompson east to Umiat and south to the 

 Noatak River watershed, between about 67°-70° N. latitude and 

 152°-166° W. longitude. 



The species of Eurytemora found in fresh water occur in a variety 

 of bodies of water, ranging in size from shallow pools to large, deep 

 lakes. Although some species appear environmentally restricted, 

 others seem ubiqmtous, and it is difficult to judge from distributional 

 data what habitats are marginal for such species. For instance, in 

 Alaska E. yukonensis occurs in the largest and deepest lakes of the 

 State (those of the Bristol Bay region) but is also found in shallow lakes 

 and ponds along the lower Yukon and Noatak Rivers, where it has 

 been collected from both open waters and submerged vegetation. 

 Other species of Eurytemora have been found abundantly in the rooted 

 vegetation of small, shallow lakes and ponds; for example, E. gracili- 

 cauda was collected in large numbers from grassy margins and from 

 beds of Arctophila of small, shallow lakes and ponds on eastern Saint 

 Matthew Island in the Bering Sea, about 60°30' N., 173°30' W. (Wilson 

 collection : August 1954, R. and R. Rausch, collectors; a iew Diaptomus 

 pribilofensis occiured in some of the weed collections). There are 

 records in the literatm'e of other species of Eurytemora associated 

 with weeds. Willey (1923a, p. 331 ; 1923b, p. 6) records a reproducing 

 population of E. affinis "amongst dwarf weeds in the littoral zone of 

 a swampy shore" of Lake St. John, Quebec, and Lowndes (1935) 

 reports E. velox as not only common among weeds but as being found 

 "attached to algae." From these observations it appears that studies 

 of freshwater calanoid copepods in geographic regions in which 

 Eurytemora is expected to occur must include exploration of more 

 than the open waters of lakes and ponds, usually considered as the 

 typical habitat for calanoids. 



Eurytemora arctica in the Cape Thompson region represents an 

 example of this need for detailed examination of weed beds. In 

 the open waters of Lake 4 (depth, 2.4 meters) large numbers of three 

 other calanoid copepods (Heterocope septentrionalis, Diaptomus arc- 

 ticus and D. pribilofensis) were collected throughout the season in 1960 

 in noticeable contrast to the small numbers of E. arctica. This erratic 

 occurrence of E. arctica in open-water samples suggested a popidation 

 localized within the lake and from which occasional individuals 

 wandered into the selected areas being routinely sampled. Therefore, 

 in 1961, other areas of the lake were investigated and larger numbers 



