Molluscs . The set of various water beings lives In a natural environment together with fishes n in interaction with them. Some of them, we already marked, are useful to fishes, others serve them as food, on the contrary, live at the expense of fishes, parasitize on them, the third - filter water, process ilovye adjournment, the rests of the died off plant and animal life, that is take active part in life circulation.
The Water world, as well as in general all live world, is rich and various. And, all live is not in a chaotic condition, and in strictly certain order, in conformity with historically died laws. And though live beings differ from each other on the structure, a way of life, environment and forms of dwelling, reproduction, movement and so on, they co-operate with each other.
All told to the full concerns and our old acquaintances whom we since the childhood have got used to see in small rivers, lakes. These are various cockleshells, molluscs and other water inhabitants.
Here, say, fresh-water cockleshells: perlovitsy, bezzubki and others. Harmful they or useful? At first sight can seem that these molluscs and fishes exist as though in itself and have to each other no any relation. Actually they have closest "mutual relations". To take, for example, a folding cockleshell and a small fish known for all - gorchak. And so, this small fish cannot simply exist without a cockleshell for like a cuckoo not itself bears caviar, and by means of special body postpones it under a bowl where it and grows ripe up to occurrence malkov.
And on it "dialogue" of folding cockleshells with fishes does not come to an end. Be not surprised, if in recently created pond which is from the nearest small river or lake on big enough distance, river cockleshells which there nobody delivered will suddenly be found out in a considerable quantity. Cockleshells the fishes delivered in a pond "have installed". The matter is that some kinds of molluscs for the moving use "services" of fishes. Here is how, for example, breeds usual river perlovitsa. It postpones eggs in the external plates of gills and bears them. The smallest folding larvae supplied bissusnymi with threads and sharp teeth are deduced from eggs in the end of the first cycle. These larvae, continuing development, remain to "winter" on cockleshell gills. In the spring they leave a cockleshell and with the help bissusnyh threads are attached to a body of fish, to its skin, fins, gills and round itself form vials. In these vials of a larva of cockleshells parasitize and thus some weeks while completely do not turn in young molluscs migrate.
After that they fall on a bottom and begin an independent way of life.
Each fisher should know that as a whole the majority of river and lake cockleshells are rather useful; animals. Being active filtration organisms, they play large role in biological self-cleaning of water and can serve as indicators of its cleanliness - if impurity of water reaches "limit", they perish.
Cockleshells are useful and, so to say, from the practical, economic point of view: their bowls go on preparation of fertilizers, a fodder flour, to exhaust... Bowls with thickness of a lamellar layer to two and more millimetres serve as a subject of a craft for the decorative purposes.
All kinds of folding molluscs at young age, and some at any stages of the development, such as drejssena, sharovka, goroshinka and others serve as a forage to numerous group of fishes. Cockleshells eat: a black cupid, leshch, a carp, a sazan. And as - vyrezub, rybets, ram, the man with a big moustache, the bull-calfe and others. Yes it and is not surprising. Meat of molluscs possesses high nutritious qualities. The quantity of fibers in them in recalculation on a solid fluctuates from 40 to 70 percent, carbohydrates - 9-16, fats - 3-l1 percent.
At the same time, fishers should know that molluscs are base of development and distribution of variety of harmful organisms. In mantijnoj cavities of the folding parasitize more than 10 kinds of different infusorians. Many molluscs are intermediate owners of larvae trematod which by transformations, getting to an organism of fishes and the person, become its parasites. In it their negative value. As experts show, during the separate periods and in separate reservoirs impurity of molluscs larvae trematod can fluctuate within the most diametrical sizes, contamination in the rivers usually keeps within five percent, in landlocked or maloprotochnyh reservoirs reaches from time to time to 36-70 percent and more.