. Ecological animal geography; an authorized, rewritten edition based on Tiergeographie auf ockologischer grundlage. Zoogeography -- Geographical distribution; Animal ecology. COMMUNITIES IN STANDING WATERS 331 the borders of the littoral regions are occasionally characterized by an abundant molluscan fauna and are then designated as sublittoral. A truly abyssal stratum, comparable with that of the sea, into which no light rays penetrate, is lacking in most inland waters, because of their shallower depth; such a stratum is found only in Lake Baikal, Lake Tanganyika, and the Caspian Sea. The de
. Ecological animal geography; an authorized, rewritten edition based on Tiergeographie auf ockologischer grundlage. Zoogeography -- Geographical distribution; Animal ecology. COMMUNITIES IN STANDING WATERS 331 the borders of the littoral regions are occasionally characterized by an abundant molluscan fauna and are then designated as sublittoral. A truly abyssal stratum, comparable with that of the sea, into which no light rays penetrate, is lacking in most inland waters, because of their shallower depth; such a stratum is found only in Lake Baikal, Lake Tanganyika, and the Caspian Sea. The deeper regions of lakes have other peculiarities besides the lack of plant growth which contribute to the unique compositions of their fauna. The amount of light which penetrates into the deeper waters is much reduced. For this reason there are modifications of color in both limnetic (see below) and bottom forms. The planarians which other-. Fig. 97.—a, Limnaea stagnalis var. bodamica from moving water; b, L. stagnalis from quiet water, normal to the arrow, beyond which the shell is weighted with cement, producing growth similar to a (after Voigt); c, L. stagnalis from a pond, the growth form produced by a strong growth of fila- mentous algae on the shell, which hinders its motion. X 2/3. wise are black (Polycelis nigra, Planaria alpina) are represented by pale yellow forms in the depths of the lakes in the Alpine foothills. The temperature is very constant in the deeper pedon as compared with that of the littoral region. In the Lake of Lucerne the tempera- ture at depths of 30 to 200 m. is not less than ° and not more than 10°; the variation at depths of 100-200 m. is only about 1°.20 Steno- thermal animals, adapted to the cold, with a few eurythermal forms, find a favorable habitat in the greater depths. There is no marked movement of water at greater depths. Because of this the floor is evenly covered with fine mud varying according to its origin, which is usually orga
Size: 1939px × 1288px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodive, booksubjectanimalecology
