Species (cont'd) 



Number captured 



1,998 



This amounts to 2, 000 Entomostraca in less than 10 

 cubic feet of water, consequently this area must con- 

 tribute materially to the maintenance of the plankton 

 in the lake. The abundance of Cyclop s leuckarti, 

 Diaptomus oregonensis, and Diaphanosoma show that 

 they were breeding prolifically in this river; all three 

 are important components of the lake plankton. The 

 number of specimens of Diaptomus minutus, which is 

 rarely found in the lake itself, suggests that it may be 

 more common in some of the lake tributaries. Evi- 

 dently the copepods found conditions much better suited 

 to their reproduction than did the cladocerans; this is 

 especially true of Diaptomus . Indeed with the excep- 

 tion of Diaphanosoma the presence of cladocerans in 

 Portage River plankton seems little more than acci- 

 dental. 



The second outside locality was the ponds within 

 the National Park on Point Pelee, on the Canadian 

 shore near the western end of the lake. The combined 

 area of these ponds reaches nearly across the point, and 

 the connecting passages as well as the ponds them- 

 selves are fairly choked with vegetation over most of 

 their surface. These ponds were examined in consider- 

 able detail for Cladocera by Bigelow (1922). He found 

 them especially adapted to the breeding of cladocerans 

 and it was the large number of species reported by him 

 that induced the present visit. The results supported 

 his statements, for the plankton from these ponds yield- 

 ed the largest number of species of any single locality 

 examined during the survey, namely 8 copepods and 

 37 cladocerans. Among the copepods Diaptomus orego - 

 nensis and Cyclops albidus Jurine were the most abun- 

 dant and nearly all the females carried egg strings. 

 This means that the ponds are as well adapted to the 

 breeding of some copepods as they are to that of the 

 cladocerans. Among the latter Sida and Acroperus 

 were most in evidence, with Camptocercus, Cerio- 

 daphnia, Eurycercus , and Simocepha lus also abundant, 

 and a long list of species represented by very few speci - 

 mens, many of these latter confined to this single lo- 

 cality and not found elsewhere. 



From the account here given it is evident that 

 somewhere in these three groups of breeding areas will 

 be found ample provision for the maintenance of 

 every species of cladocera found in the lake plankton, 

 and for all the copepod species except Limnocalanus . 

 That copepod, together with Mysis and Pontoporeia 

 have practically no connection with the marginal zone, 

 but find their breeding areas in the deeper portions of 

 the lake. 



Marginal Organisms 



Copepods 



Only a single genus of harpactid, Canthocamptus, 

 is represented in the marginal plankton, but 5 species 

 were found within the lake drainage. One of these, 

 C. trispinosus, was taken in the mouth of a small 

 creek at Cedar Bay on the Canadian shore and at Lac- 

 kawanna Pond in the northern outskirts of Buffalo. It 

 has never before been reported from any locality in 

 America but is common in many European countries. 



Of the genus Cyclops, using the old nomencla- 

 ture, 9 species were obtained, and it is evident from 

 their abundance that they are among the most impor- 

 tant copepods of the marginal zone. The species C. 

 serrulatus F ischer was the most widely distributed, 

 being found in every locality examined and listed as 

 abundant in half of them. Next come C. bicuspidatus 

 Claus, C. leuckarti Claus, and C. albidu s Jurine, 

 which were found in about two -thirds of the localities 

 and often in large numbers. The 368 specimens of 

 C. leuckart i in the single vertical haul in the Portage 

 River at Port Clinton, Ohio, was the largest number 

 of any Cyclops species obtained at one locality with- 

 in the marginal zone. Although the species C. 

 viridis J urine was captured at 13 of the stations its 

 numbers were very small except in Sandusky Bay, 

 and hence that locality is probably one of its breed- 

 ing places. The remaining species are not widely 

 distributed and are not found anywhere in sufficient 

 numbers to give them more than petty economic 

 value. 



In the genus Diaptomus the species D. oregonen - 

 sis is by far the most abundant, and the Portage River 

 record given above shows that it breeds at some lo- 

 calities in this zone in very large numbers. This 

 fact assumes greater significance when contrasted 

 with its entire absence from the littoral and lacustric 

 zones. On the other hand the species D. ashlandi 

 and D. sicilis, which were so abundant in those two 



4 



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