Aquatic 
Lite 109 
Red Planorbis, Planorbis corneus rubra, 
the Paper Shell, Lymnea auriculana; 
and the commoner river operculates of 
value in his tanks. Snails in a small tank 
soon deteriorate in size. ‘This is prob- 
ably not so much due to inbreeding as to 
the concentration of certain salts in the 
water, as the water evaporates and fresh 
is added. ‘The same is more or less true 
with fishes. Ergo: siphon a little water 
—always from the bottom—occasionally, 
and add a little lime (plaster of paris) 
for shell structure. 
And now a word or two on ecology. 
Snails are distributed in communities. In 
a city we have the Gold Coast commu- 
nity, the German district, Swedish dis- 
trict, Irish section, ghetto, Italian colony 
and Polish community. With snails like- 
wise. An illustration shows a cross-sec- 
tion of a stream at a bend. On the out- 
side of the bend is a steep bank, deep 
water, current and large stones on the 
bottom. It is clinging to these stones that 
the long river snail, Pleurocera elevatum 
may be found. In midstream, with shal- 
lower water, less current, smaller stones 
and some gravel, we find the live-bearing 
Campeloma integrum. On the inside of 
the bend, with shallow water, little cur- 
rent, bottom of fine sand and gravel, we 
find the small bivalve Sphaerium stami- 
neum. 
The longitudinal section of a river is 
interesting. At and near the mouth we 
normally find a pond condition and ani- 
mals of the pond community. Here we 
find sluggish water, sedimentary bottom, 
vegetation of the emerging and floating 
type, and decaying vegetation on the bot- 
tom. The snails and fishes here are of 
the still-water or sluggish water type. 
Lymnaea stagnalis, with black shell, is 
found here, and other eaters of decaying 
vegetation. 
As we go upstream we find more cur- 
rent, fewer emerging plants, more of a 
rocky bottom, and a different type of 
snail. ‘Then comes a condition still far- 
ther upstream, of more current, rocky or 
sandy bottom, vegetation only along the 
banks, etc. Farther on we find a shallow- 
water condition, more current, protrud- 
ing rocks, and riffles here and there. The 
fishes and snails here are yet different. 
At the head of the stream is a spring- 
breok condition, with all the animal life 
that goes with it. It is said that if the 
upstream snails be brought downstream, 
and the downstream snails brought up- 
stream, that they will gradually return to 
their original habitat. Local obstructions, 
such as dams or deep pools, may cause a 
local pond condition. On the other hand, 
a hard layer of rock may cause a rapids 
condition well toward the river’s mouth. 
The snails here are of the respective 
kinds found in pools and in rapids. 
Long River Vivioarous Small bivalve 
Snai nat i : 
Pleuracera elevutim Campeloma integrum “Sphaerium slaminaeum 
44 
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Cross Section of a Sluggish Stream at a 
Curve, Showing Distribution of Snails 
(By the Author, after Shelford) 
Young ponds, with bare bottom, and 
no plants but possibly chara, contain very 
Older ponds, of the sub- 
merged vegetation association, with bul- 
rushes on the border, and other aquatics 
coming in, become the homes of a few 
varieties of snails. These snails are of 
the gill-breathing type, contain no oper- 
culum, and may be relied upon to eat 
plants. In mature ponds, say of the 
few snails. 
