Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XXIII (1927)
Harring, H. K.; Myers, F. J.
The rotifer fauna of Wisconsin. IV. The Dicranophorinae, pp. -Plate 49 ff. PDF (41.5 MB)
Harri 674 Wisconsin Academy of Sciences, Arts, and Letters. one week among the hard water lakes and ponds around Madison, Wisconsin; the same number was gathered in one hour from a small, soft water lake at Eagle River, in north. ern Wisconsin. The pH range of individual species appears to be as a rule quite narrow, from 2 to 3 units pH; a few are able to thrive through a greater range, but, as far as may be judged from field observations, they are not numerous. Perhaps the most striking fact observed is the total disap- pearance of the genus Brachionus in acid waters, with the single exception of B. polyacanthus. It is now quite evi- dent why no Brachionids were found in Johansen's and Jessup's collections in Alaska; the tundras are covered with sphagnum growing knee-high and decaying rapidly, with continuous accumulation of humic acid, leaching into the shallow pools and ponds. Two Euchlanids are especially interesting in this connection; E. triqutetra is ubiquitous in alkaline waters, but not in acid, while E. pellucida is just as abundant in acid water, but has never been found in alkaline. The explanation of the rarity of certain rotifers is now fairly simple: acid waters are not common where rotifers have hitherto been studied most intensely. Thus, Tetrasiphon hydrocora ( - Copeus spicatus) is usually ac- counted rare; as a matter of fact it is common in acid water regions. Brachionus polyacanthus was long supposed to be non-extant; it is simply an acid water form. The same is true of Proales doliaris, Notommata saccigera, Pleurotro- cha robusta, Cephalodella globata, C. eva, Lecane brachy- dactyla and L. ligona, not to mention a host of recently de- scribed species; all are acid water animals, and it would be useless to search for them in alkaline ponds. It will now be fairly evident that ,the large number of new rotifers we have found is not due to any superior skill or esoteric in- formation, but solely to the fact that we have been fortu- nate enough to have had access to numerous bodies of water with different degrees of acidity. The years given to the gathering of evidence that might establish a correlation between rotifer distribution and hydrogen ion concentration have gradually brought forth a considerable body of literature, bearing more or less di- rectly on our subject. A few of the most important papers are brie sions. Skad concent logical Flagelli are lim contribi on a sp life hisi of the v its dis- latter ii ing ims long sta Attew which, clear uis organis hydroge A vp n optimuh the depn conpentr in part Ipowers. ability knowing fauna is in this e satisfied, values fz 'Hydroph Bedeutung Int. Ver. Li Ueber di Bedeutung. ' Wirkuni intermedia Uber die' intermedia peratur un Reeb., vol. I.. '5v I II
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