What do freshwater mussels eat? An introduction to the feeding habits of freshwater mussels
Freshwater mussels are the collective name for a group of animals in the family Unionidae of the phylum Mollusca, distributed in Asia, Europe, North America and North Africa, living on the bottom of freshwater lakes, ponds, rivers and other waters, semi-buried in mud and sand. Because they have many farming advantages and development prospects, they have become the preferred farming project for many farmers. Let's take a look below at what freshwater mussels eat!
What do freshwater mussels eat
The food of freshwater mussels is mainly unicellular algae, protozoa and organic detritus, such as rotifers, flagellates, Euglena viridis, Chlorococcum, Scenedesmus, Navicula, dinoflagellates, Tetragonium, spindle-shaped diatoms, Actinastrum, crustacean fragments and plant leaves. What is easily digested is mainly diatoms. Mussels cannot actively chase food; they rely on the opening and closing of the shell and the beating of the cilia on the inner side of the mantle and on the gills to create a water current, and the food enters the mussel body with the water. The food enters the mantle cavity with the water, and the particles move upward along the gill filaments to the base of the gills, then forward to the labial palps. After selection by the labial palps, small particles enter the mouth, while large particles move backward along the inner gill margin, at the junction of the two gills, into the mantle scar to the posterior end, and are expelled from the body when the two shells snap shut. According to some statistics, the water flowing into a mussel's body each day can reach 40 liters.
The habitat environment of freshwater mussels
In the natural environment, mussels generally live in rivers, lakes, ponds, streams and other muddy, sandy or gravelly bottoms. When it is cold in winter and spring, they use their hatchet-shaped foot to dig into the mud, so that part of the mussel body is buried in the mud and sand, with the anterior ventral margin downward and the posterior dorsal margin upward, exposing only the posterior margin of the shell for breathing and feeding. When the weather is hot, most of them are exposed outside the mud. Anodonta generally live in muddy bottoms, in still or slow-flowing, relatively fertile water with a pH of 5 to 9.
The digestive system of freshwater mussels
The mouth of the freshwater mussel is located below the anterior adductor muscle and is a horizontal slit. On each side of the mouth there is a pair of triangular labial palps, which are large and densely covered with cilia, with sensory and feeding functions. Behind the mouth is a short and wide esophagus, connected below to the expanded stomach, around which there is a pair of livers that can secrete amylase and sucrase, with ducts entering the stomach. Behind the stomach is the intestine, coiled within the visceral mass, then entering the pericardium, with the rectum passing through the ventricle, and the anus opening on the posterior adductor muscle, near the excurrent siphon. Between the stomach and intestine there is a crystalline style, which is a slender rod-shaped structure, thicker at the front end, with the tip shape varying greatly, appearing as a fine point, expanded, hooked, or coiled. The crystalline style is located in the intestine, with its front end protruding into the stomach and connecting with the lower part of the gastric shield. The crystalline style may be stored food; under conditions of food shortage, the crystalline style of the freshwater mussel disappears after 24 hours, and after feeding is resumed, the crystalline style is restored after several days.
Farming methods for freshwater mussels
1. At present, freshwater mussel farming mostly uses hanging culture and cage culture. Hanging culture methods include single hanging culture and string culture with more than two mussels hung on one line. The number in cage culture depends on the size of the cage (net cage, net clip); generally, it is suitable when each mussel can touch the bottom of the cage.
2. For pearl-cultivating freshwater mussels, generally 800 to 1200 per mu in ponds and 600 to 800 per mu in open waters. The specific farming density depends on body weight and fatness. Physical, chemical and biological factors such as water flow and water depth should be increased or decreased appropriately according to the size of the mussels.
3. Freshwater mussel farming has become the main production content of the comprehensive development and utilization of the open-water fishery body in our city. Ponds mainly used for pearl cultivation can be appropriately stocked with grass carp, bream, crucian carp, mandarin fish, yellow catfish, etc., and a small number of silver carp and bighead carp can be added, so as to fully tap the production potential of the water body.