The common name for shellfish of the genus Anodonta in the subfamily Anodontidae of the mussel order Lamellibranchia. Distributed in Asia, Europe, North America and North Africa. Most of them can naturally form pearls in the body.
The mussels are oval and ovoid in shape. Shell thin, fragile. Both shells are swollen, the back of the back sometimes with hind wings. The top of the shell is broad, slightly elevated, located in the middle or front of the dorsal margin. Shell surface smooth, with concentric growth lines or green radial lines from shell apex to ventral margin. Gelatinous part narrow, without teeth. Axillary feet well developed. Dioecious. Eggs are fertilized in the spring, and can develop into larvae in about 2 months, which can be discharged from the body. If the eggs are fertilized in the fall, the embryonic body will overwinter in the mother's body and develop into hooked larvae in the spring of the following year, which will be parasitized on the fish body after the hooked larvae are discharged from the body and detached from the body of the fish after the development of young mussels, sinking to the bottom of the water, and then live freely. The meat is edible, and it is also the natural bait for fish and birds, and the feed for livestock and poultry. Some species can be used as freshwater beads.
Chinese habitual species of dorsal horn toothless mussel (A. woodiana woodiana) shell length of up to 200 millimeters, the shape of the horns protruding ovoid, the two shells are swollen, the back edge of the rear of the wing, the back of the three rib veins from the top of the shell, the lowest rib vein is located in the shell on the midline. It mostly inhabits silty bottoms, slow currents and still waters, and is found in rivers, lakes, reservoirs and ponds. It is dioecious. In Jiangsu in March gonadal maturity, mature eggs in the gills of the female body in the fertilization and development, about in April to May hook medium larvae mature and discharged from the body, parasitic in the body of the fish, to be developed into a young mussel, sinking to the bottom of the water life. Freshwater pearl-breeding mussels, but the quality of the beads is inferior. Meat for food. Shells are used in traditional Chinese medicine.
External morphology
Toothless mussels have a two-valve ovoid shell, left and right isomorphic, mirror symmetry, shell collar protruding. The anterior end of the shell is more rounded, the posterior end is slightly truncated, the ventral line is curved, and the dorsal line is flat. The gibbous part is toothless, and there is a ligament on its outer side, relying on its elasticity, which can make the two shells open. The growth lines on the shell surface are obvious.
The inner surface of the shell has muscle scars for muscle attachment. Coat scar parallel to the ventral margin of the shell; 3 muscle scars on the anterior upper part of the shell, the largest one oval, the anterior closed-shell muscle scar; a small, slightly triangular anterior retracted-foot muscle scar on its posterior upper margin; and an extensor-foot muscle scar on its posterior lower line. At the posterior end of the shell near the dorsal margin there are two muscle scars, the larger one is the posterior closed-shell muscle scar, oval, and a small one at its anterior upper margin is the posterior retractor muscle scar.
Envelope
The inner surface of the two shells is two thin ectodermal membranes, which surround the body of the mussel, and between the ectodermal membranes is the ectodermal cavity. The inner surface of the membrane with cilia, cilia swinging in a certain direction, causing water flow. The two pieces of membrane at the rear end of the slightly protruding, synthetic outflow pipe and into the water pipe. Inlet tube in the ventral side, the mouth is elongated, the edge is folded, there are many papillate sensory organs; outlet tube is located in the dorsal side, the mouth is small, the edge is smooth.
Feet
Hatchet-shaped, laterally flattened on the right and left sides, rich in muscle, situated on the ventral side of the visceral mass, extending forward and downward. It is the organ of locomotion of the clam.
Muscle
Corresponding to the inner surface of the shell muscle scars, can be seen anterior adductor (anterior adductor) and posterior adductor (posterior adductor), for the thick columnar muscle, connecting the left and right shell, its contraction can make the shell closed. The anterior retractor (antenor retractor), posterior retractor (posterior retractor) and protractor (pprotractor) are attached to the foot at one end and to the inner surface of the shell at the other end, which enable the foot to be retracted and extended.
Digestive system
The mouth is situated under the anterior closure of the perfectus muscle, a transverse slit. On each side of the mouth is a pair of triangular labial plates, large, densely ciliated, with sensory and feeding functions. After the mouth for a short and wide esophagus, under the expanded stomach, stomach around a pair of liver, can be secreted amylase, sucrase, there is a conduit into the stomach. The stomach is followed by the intestine, which is coiled in a visceral mass and posteriorly enters the peripheral heart, the rectum passes through the ventricle, and the anus opens on the posterior occludator muscle, near the efferent duct. Between the stomach and intestines there is a crystalline rod, an elongated rod, thicker at the anterior end, with a variable apical morphology, which is apiculate, dilated, hooked, coiled, and so on. The crystalline rod is located in the intestine, and its anterior end protrudes into the stomach, where it meets the lower part of the gastric shield. Crystalline rod may be stored food, mussels in the lack of food conditions, 24 hours after the disappearance of the crystalline rod, re-feeding, a few days after the crystalline rod to restore the existence. Mussels feed on organic matter particles, rotifers, flagellates, algae, and small crustaceans.
Respiratory organs
In the coat cavity of the mussel body on each side with two lamellar valvular gills (Lamina), the outer valvular gills shorter than the inner valvular gills. Each defense gills by the inner and outer two gill flap (lamellae) constitute, its anterior and posterior edges and ventral edges fused into a "U" shape, the dorsal edge of the gills of the upper chamber (suprabranchial chamber). The gill flap consists of many longitudinal gill filaments (Branchial filament), the surface has cilia, the gill filaments have transverse filament intervals (interfilamenta junction) connected, there are small holes on the gill holes (ostrium). Between the two gill flaps there are flap intervals (interlamellar junction), the gill cavity between the gill flaps is separated into many small tubes called water tubes (water tube). There are blood vessels in the interlamellar junction and the interlamellar junction, and there are also blood vessels in the gill filaments and a few chitinous rods that play a supporting role.
Because of the gills and the outer coat membrane on the cilia swing, cause the water flow, water from the inlet pipe into the outer coat cavity, through the gill holes to the gill cavity, along the water tube up to the upper gill cavity, backward flow, through the outlet pipe out of the body. When the water passes through the gills, gas exchange takes place. The coat membrane also functions as an aid to respiration. Every 24 hours through the mussel body of water up to 40L, gill surface cilia can filter food particles in the water, sent to the lips and then inlet. Therefore, the gills can still assist in feeding. The gill cavity of the external gill is the place where the fertilized egg develops until the formation of the hooked larva.
Circulatory system
Consists of the heart, blood vessels, and blood sinuses. The heart is located in an elliptical pericardial cavity on the dorsal side of the visceral mass and consists of an oblong ventricle and two thin-film triangular auricles on the left and right. The ventricle extends anteriorly and posteriorly with a large artery each. The anterior aorta extends forward along the dorsal side of the intestine, the posterior aorta extends posteriorly along the ventral side of the rectum, and later branches into small arteries (artery) to the trochlea and all parts of the body. Finally, they converge in the blood sinuses (coat sinus, pedunculated sinus, central sinus, etc.), enter the veins, enter the kidneys through the renal veins to eliminate metabolites, then enter the gills through the gill veins to carry out oxygen-carbon exchange, and return to the auricles through the gill veins. Part of the blood enters the cardiac auricle by the socket vein, i.e., the coat circulation.
Toothless mussel blood contains haemocyanin (haemocyanian), oxidized blue, colorless when reduced, and its ability to combine with oxygen is not as good as hemoglobin ___ general mollusks 100 ml of blood containing oxygen is usually no more than 3 mg. blood contains amoeboid cells, phagocytosis. Therefore, in addition to transporting nutrients, blood also has the function of excretion. Amoeboid cells aggregate and their pseudopods bind to each other to coagulate the blood (mussels do not have fibrinogen in their blood).
Excretory organs
The mussel has a pair of kidneys, which are formed by specialization of the posterior nephron ducts, also known as the organ of Bojanus, and a pericardial gland, also known as the Kebers organ. Kidneys are located in the pericardial cavity on the ventral surface of the left and right sides, each consists of a spongy gland and a thin-walled tubular body with cilia, in the form of a "U" shape. The former is on the lower side, and the renal orifice opens into the pericardial cavity; the latter is on the upper side, and the renal orifice opens into the anterior part of the supra-gill cavity of the endocardial gills. Pericardial glands are located in the anterior wall of the pericardial cavity, which is a mass of branched glands composed of flat epithelial cells and connective tissues, which are rich in blood, and can collect metabolites, which can be discharged into the pericardial cavity, and then discharged out of the body through the kidneys. Phagocytes between the tissues, also have an excretory function.
Nervous system
The toothless mussel has three pairs of ganglia. Below the anterior closed shell muscle, on both sides of the esophagus for a pair of cerebral ganglion, very small, is really a merger of cerebral ganglion and lateral ganglion to form, can be called lateral cerebral ganglion. At the anterior edge of the foot against the upper buried in the foot for a pair of long foot ganglia, the two combined. The dirty ganglion is a pair of healed, butterfly-shaped ganglia, located under the epithelium of the ventral aspect of the posterior closed shell muscle, and is larger. The three pairs of cerebral, pedunculated, and visceral ganglia are connected by a neural ligament, and the cerebral-visceral neural ligament is longer and more pronounced.
The senses of the mussel are not developed, and there is a balance capsule near the pedunculated ganglion, which is formed by subsidence of the pedunculated epithelium. There is an otolith inside, which is responsible for the balance of the body. The epithelium above the dirty ganglion becomes the sensory epithelium, equivalent to the olfactory detector of gastropods, for chemoreceptors. In addition there is a distribution of sensory cells around the outer coat membrane, labial lamellae and water tubes.
Reproductive system
Mussels are dioecious, the reproductive glands are located around the dorsal intestines of the foot, in the form of grapelike glands, spermathecae milky white. The ovary is yellowish. The reproductive ducts are open, and the opening of the genital pore is very small below the posterior part of the renal pore.
Reproduction and Individual Development
The reproductive season of the mussel is generally in the summer, and the spermatozoa are fertilized in the gill cavities of the external gills. Fertilized eggs will not be washed out by the water flow due to the adhesion of the mother, but remain in the gill cavity to develop. Therefore, the gill cavity of the external gills is also called the marsupium. After completely unequal cleavage (spiral type), it develops into a blastocyst, which forms a protozoan embryo by external encapsulation and invagination, and develops into a larva, which overwinters in the gill cavity. Observation of the early embryonic cells of the dorsal horned toothless mussel identified chromosomes 2n=38 or 2n=37 (chromosome 19 is single), the difference between the two is unknown and may be related to the sex chromosomes (Ma Qingfu et al. 1987). In the following spring, the larvae hatch and develop into the mussel's characteristic hook-mediated larvae (equivalent to the facultative disc larvae of other valviparous species). The larvae are bivalve. There is a well-developed closed-shell muscle, and the ventral margins of the shell each bear a strong about hook and are dentate. The center of the abdomen bears a thin, sticky filament called the pedipalp filament. The lateral margins of the shell bear bristles, which are sensory. The larva has a mouth without an anus. The larvae can swim by opening and closing the bivalve shell. Freshwater crab wrasse (Rhodaus sinensis), etc., with a long spawning tube inserted into the mussel's entry tube, spawning in the mussel's coat cavity. The hooked larvae of such mussels have the opportunity to come into contact with the paraphyletic fish and can parasitize the gills, fins, etc. of the fish. The skin of the fish is stimulated by it and proliferates abnormally, encasing the larvae in its scarf and forming a capsule. The larvae suck nutrients from the fish through the epithelium of the coat membrane. After 2 to 5 weeks, it metamorphoses into a young clam, breaks the capsule from the fish and sinks to the bottom of the water. After 5 years to reach sexual maturity. Later still continue to grow.
One day in 1988, a farmer in Henan Province by chance from the river ditch picked a 13.8 pounds of mussels, the curious owner to take home to eat, it will be in the yard to dig a small pond to feed up. On the third day, the big mussels escaped, the owner of the effort, only from the dismantling of the courtyard wall below to find. In order to prevent the escape, the owner tied a rope to its shell. But after a day, when the big mussel had just worn off the rope to escape, it was again found by the master. This time the owner of the gas fire, immediately ready to kill it, cooked into a feast on the delicacies, but coincidentally an aquatic science and technology personnel know, he told the owner, although the mussels are surprisingly large, but it is only 12 years old, is the youth of the vigor of the period. So, the owner of the people in the future to feast their eyes, for it to build a new "villa", more concerned about its growth.
[Edit paragraph] therapeutic role
Taste sweet and salty, cold, into the liver, kidney meridian;
Hot detoxification, nourishing yin and eyesight effect;
Can be cured of fever, thirst, blood, bring down the hemorrhoids, hemorrhoids and fistulas, red eyes, eczema and other diseases.