Molluscs door (Mollusca) is second only to the animal kingdom Arthropoda second door. The door animal body soft, symmetrical, unsegmented, by the head, foot, visceral sac, mantle and shell composed of five parts. Because most are covered with a variety of in vitro mollusk shells, so known shellfish. The door is divided into eight classes of animals, there are more than 10 million, is widely distributed, from boreal, temperate to tropical, from the ocean to the rivers, lakes, from the plains to the mountains, everywhere, such as abalone, baby, snail, snails, clams, oysters, clams, octopus, squid and so on. Since most mollusk shells gorgeous, fresh meat, nutritious, and easier to catch, so far in the ancient hunting and fishing times, had been the use of human beings, many of them edible, medicinal, agricultural, arts and crafts industry use, There are also some types of toxic and can spread disease, damage crops, damaged buildings and harbor transportation facilities, harmful to humans.
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Structural features
软体动物门 结构特征
软体动物门 结构特征
软体动物门 结构特征
软体动物门 结构特征
1 head: Located in front of the body. Some kind of sluggish original head underdeveloped, only the mouth, with no obvious physical boundaries, such as chitons, etc.; Some burrowing species or sessile body is completely coated in the mantle and shell, the head of degradation, such as mussels, oysters, etc.; some of the more evolved kind of head movement agile development, differentiation obviously, having tentacles and eyes and other sensory organs, such as snails, snails and squid. 2, Foot: is located in the ventral body movement organs, with different lifestyles presented in different forms: some kind of foot plantar surface smooth, suitable for crawling on land or underwater, such as gastropods; some kind of foot was ax blade shape is conducive to dig sediment, such as Lamellibranchia; Some sessile species foot degradation, such as oysters Branch; also some kind of foot atrophy, loss of motor function, but there is enough silk glands that secrete byssus, attached to the outer material life, such as Mytilidae, fan Beca, etc. In cephalopods, the foot was born in the head, and some special into the wrist, above there have been many sucker for prey organ, and a part of the metamorphosis into a funnel, suitable for swimming life, such as squid and octopus. A few species foot side (ie, side foot, parapodium) into special sheet, swimming, called wings or fins, such as pteropods (Pteropoda). Foot usually birth balancer, some species in the upper foot has many tentacles students. 3, visceral sac: Located in the back of the body, including the stomach, intestine, digestive gland, heart, kidney, gonads and other organs, as the mantle and shell are coated. Most species of visceral sac is symmetrical, but some twisted into a spiral, losing symmetrical shape, such as snails. 4, the mantle: the body back to the ventral skin folds extending a protective organ surface formed by the inner and outer skin, in the middle of a small number of muscle fibers and connective tissue. There mantle cavity between the mantle and the visceral, coat gills and mouth cavity, anus, kidneys, gonads openings. Mantle edge structure is very complex, often with various shapes tentacles, and some species have coats eye. Ciliated epithelial cells within the mantle, ciliary beat, causing the water to make the water cycle in the jacket cavity, in order to complete the respiration, excretion, feeding, etc. About two _set_s of twelve films often heal at the trailing edge, forming a water hole (exhalant siphon) and into the water hole (Inhalant siphon). Some species out of the water holes extend into a tube, called the outlet pipe and the outer shell protruding into the pipe. 5, shell: in vitro with an important feature of mollusc shells, so the study of mollusks and shellfish, also known as school discipline (Malacology). Shell is formed from the mantle secretion of calcium and organic matter. Most species have a shell, such as gastropods, dig enough classes, there are many species have two shells, such as Lamellibranchia, very few species have eight shells, such as multi-plate Gang; also have some kind of shell degradation into the inner shell, and some shell. Shell morphology varies greatly with the type, and some were cap-shaped; helical snails; TUNNELING Diplopoda tubular; Lamellibranchia of ro_set_te, which is to distinguish one type of important features. The main ingredient is calcium carbonate shells and a small amount of shell matrix (conchiolin, also known as shell elements) composition. Shell structure can be divided into three layers: the outermost layer of the stratum corneum (periostracum), thin, transparent, glossy, constituted by the shell matrix, without the acid-base erosion, protect shellfish; middle layer of the shell interstitial layer (ostracum, also known as the prismatic layer, primatic layer), accounting for the majority of shells from prismatic calcite; innermost layer of the shell bottom (hypostracum, ie nacre layer, peral layer), shiny, by the leafy aragonite (aragonite) composition. The outer and middle secreted form of the mantle edge, can be gradually increased with the growth of animals, but not thickened; inner membrane secretion from the entire _set_ can be increased with the growth of the individual thickness. Pearl is the nacre layer. When the mantle by the tiny sand particles and other foreign matter intrusion stimulation of epithelial cells by stimulating foreign body that is at the core and the mantle epithelium into the connective tissue in between, into the epithelial cells divide to form their own pearl sac, sac that secrete nacre , layer by layer, the nuclear complex packet bit gradually formed pearls. According to historical records 2200 years BC, China had fresh sterile beads records ("Yugong articles"), Guangxi Autonomous sterile beads famous since ancient times, picking began in the Han Dynasty. Chitin and the cuticle layer of non-continuous growth, the food temperature on the secretion function of the mantle, the growth rate is different from the shell, so the shell growth lines formed on the surface, the growth speed is shown.
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系统器官
Mollusc digestive system including the mouth, esophagus, stomach, intestines, anus and subsidiary glands. Mouth for a simple opening or with more developed muscles. Developed labellum the port of Lamellibranchia around; the cephalopods the mouth film; except Lamellibranchia, piece both jaw (mandible) oral and radula (radula). Located in the back of the gastropods, or just a jaw-chip, or two in the mouth on both sides, cephalopods, two jaw pieces are located at the back of the oral ventral the jaw piece auxiliary prey. Radula molluscs unique organ, located in the floor of the mouth, tongue protrusion (odontophore) surface consists of rows of horny teeth shaped like Cuodao. Radula feeding the telescopic movement before and after scraping food. Radula morphology, including small tooth shape, number and arrangement of class, one of the basis for the distinction between family and genus. The small teeth Horizontal many rows of small teeth constitute radula. Each crossbar has a central tooth, the left and right side tooth one or several edges HOPEFULLY teeth one or more pairs. The teeth tongue small teeth arranged in said gear, such as tooth-type of the Chinese Yuan snail (Cipangopaludina chinensis) 2.1.1.1.2. Oral cavity, salivary glands opening the mouth down the esophagus, esophagus often form crop. Esophagus accessory glands, such as gastropods Loeb spirit glands, venom gland. The esophagus down for the stomach, the stomach is usually a flower oval pocket, strong contraction of muscle in its inner wall. Some types of gastric parietal Health in Gastropoda be gill suborder, chewing board. Lined nudibranch, some species with several quality teeth. THE the stomach of Lamellibranchia often an pyloric caeca, including crystal rod. Stomach with the opening of the main digestive gland liver. The rear of the stomach to intestines, gastrointestinal often a valve separately. The end of the intestine for rectal, some species in the rectum to a subsidiary opening of the anus. Mollusk's digestive tract is developed, and a small number of parasitic species (within Send a snail, Entocolax) degradation. Reproductive system
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Habits
Molluscs living habits varies by species. Gastropods in terrestrial, freshwater and marine are distributed Lamellibranchia live only in freshwater and marine, and other groups are completely live in the ocean. Their lifestyles are: 1, planktonic life: Camp species drift in this life are floating in the ocean off life. Generally smaller individuals, thin shells or no shells. Some special types of feet into fins, such as pteropods and many different species of cephalopods. Some species secreted by the foot of a floating capsule carrying animals floating in the ocean, such as sea snails. Because they are drift, so distribution is closely related with the ocean currents, such as the distribution of Chinese coastal pelagic mollusks greatly affected by the TWC, distributed by the strong potential of the North Stream, when warm southerly distribution potential weak. 2 swimming life: Camp species can swim and fish life, like long-distance migration, such as cephalopods cuttlefish, squid, octopus in the ocean, wrist and foot special funnel into the sides of the trunk portion of their produce fin , by the role of the funnel spray and fins can swim quickly and smoothly. Some Lamellibranchia (such as scallops, moon shell, filing clams, etc.) Though But swimming life, but when necessary, can be opened and closed with sharp shells and jackets tentacles role for butterfly swimming in the sea. 3, benthic life: the vast majority of benthic mollusks. They sprawling underwater, or in the sediment fixation. Some kind of camp life on the bottom, such as abalone, snails slug, snail, snails, conch and other surfaces in the rock or mud beach crawling; mussels, scallops, etc. with enough wire attached to the seabed rocks or other foreign objects; oysters , ape head clams, clams and other sea daisy with shells fixed foreign objects on the seabed. Some species within the camp at the end of life, for example, many Lamellibranchia (clams, clams, cockles, Ying clams, razor clams, etc.) developed by foot digging sand, buried in the bottom of the body as a whole habitat, water pipes and by the end of Table communication. Many species in the perforated timber, rocks, shells, coral reefs and other hard sediment in life, such as stone clams, sea bamboo, open clams Chuanzao rocks, shells, bamboo shoots and boat maggots Mate Hai Chuanzao timber. 4, parasitic life: some as spurious, such as cylindrical spiral step parasitic on echinoderms wrist band ditch; Some of the parasite, such as the inner shell snail parasites in the anchor cucumber esophagus.
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The main Gang
7, gastropods (Gastropoda): mollusks in the largest class, there are more than 100,000 kinds. Life in marine, freshwater, and terrestrial distribution throughout the world, a few species of parasitic as Send the screw (Entocolax) within light screw (Melanella) inner shells (Entoconcha). Except pteropods head are developed with one or two pairs of tentacles, a pair of eyes. Look unfamiliar at the base of the antennae, the middle or the top. The radula mouth developed for feeding, drilling. Foot located on the ventral surface of the body, generally used for crawling, swimming, sometimes by foot contraction and jump. Except a few species, and more with a shell. Shell often isolated spiral hermaphrodite or allogeneic, oviparous. Aquatic those with gills, kind of breathing replace them with the mantle of the terrestrial surface, from the pulmonary effects. The shells of gastropods developed diverse. Some housing, some of the inner shell, and some shells completely degraded. Generally spiral, left-handed or right-handed. The foot often can secrete a horny or calcareous operculum conceal shell mouth, the protective effect. Gill subclass (Prosobranchia), after gill subclass (Opithobranchia), and lung snails subclass (Pulmonata). 8, cephalopods (Cephalopoda): All seafood carnivorous. Body symmetrical, separately, feet, torso three parts. Head developed on both sides with a pair of well-developed eye, original species with housing, most of the inner shell or no shell; foot Born in the head, specially evolved into the wrist, and the funnel, so called cephalopods. The funnel is located between the head ventral, head and torso. Feathery gills or two pairs atrial appendage and the number of kidney and gill. With cartilage. The oral jaw piece radula. Centralized nervous system developed senses. Closed tube circulatory system. Direct happen. About 700 existing species of cephalopods, fossil species in more than 10,000 kinds. Including Nautilus subclass (Nautiloidea), and interior angles Danya Gang (Endoceratoidea), in the bead angle Danya Gang (Actinoceratoidea), daisy-Danya Gang (Ammonoidea), sheath shaped sarcopterygii (Coleoidea) and other. Mollusca, may be classified, but the classification of the position undetermined bamboo stone the Gang (Tentaculita) and the soft tongue snail Gang (Hyolitha) Two Programs.
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Evolution
The mollusks seafood species ontogeny spiral cleavage and Trochophore, and excretory organs after renal tubular These features are especially polychaete annelid approximate. Therefore, there is reason to think mollusks and annelids have a common origin in the system occurred, inactive lifestyle in the long-term evolution toward development, thus somites disappear shells, moving organs and nerve senses tend to decline . Veneer Gang in mollusks, no board outline and board outline more primitive and developed these types of secondary body cavity approximation ladder nerve; Some lanes are worm-shaped, shell, many organs, such as gills, kidney, shell, etc. nearly as good as the sub-section alignment phenomena. The presence of these primitive traits that the original ancestors of their proximity to mollusks, independently developed a. More primitive gastropods, active lifestyle, the head developed. The lifestyle of Lamellibranchia activities without a head shield, but the original species with gills, foot toe-surface Gastropoda close. TUNNELING foot outline head obvious, enveloped in the embryo as the two, after healing of the tubular-shaped, paired kidneys, brain section and the side ganglion separately, these show that close to the original bivalves, but TUNNELING foot class no gills, heart, Shell cylindrical, display and other Gang animal evolution more distant, earlier ceded one. Cephalopods an ancient group, the origin and early fossil species. They reproductive cavity and body cavity interlinked, like board Gang; ontogenesis in early embryonic kidney, like multi-board outline and no board outline; reproductive ducts from the body cavity catheter also deemed plates Gang. Cephalopods characteristics of the original molluscs are close to the original species of mollusks. Cephalopods organic structure, the complexity of the nervous system is highly centralized, and is surrounded by a cartilaginous; eye structure similar to vertebrate basic circulatory system for closed-tube; occur directly larval stage. Cephalopods both primitive traits, but also a high degree of evolutionary characteristics, suggesting that they may be an early separation of the development of an independent branch along a more active lifestyle.
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Economic significance
There are many types can be exploited for human benefit humanity, but there are also many kinds of crimes against humanity often caused economic losses in the mollusks. Beneficial aspects of Food value: seafood, abalone, jade snail, Xiangluo, Rhodospirillum, Babylonia, snail, cockles, mussels, scallops, Jiang pectinata, oysters, clams, clams, clams, razor clams, cuttlefish, squid, production of octopus, freshwater snail, snail, mussels, clams, terrestrial habitat snail meat is delicious, rich in protein, salts and vitamins, has a high nutritional value. Medicinal value: abalone shells (TCD abalone) to treat diseases of the eye; baby shells called "Hai Ba can eyesight detoxifying; pearl is a precious Chinese herbal medicines, calming liver yang, Qingrejiedu the town Anshen, cough and phlegm, eyesight analgesic and convergence vitality; squid shells called cuttlebone, trauma, heart disease and stomach problems can be treated, and to stop bleeding; cockles, oysters, clams, blue clams and other shells Chinese medicine commonly used medicinal herbs. Can be extracted from abalone, conch, sea snails, clams, oysters, squid and other antibiotics and anticancer drugs. 3, the value of agriculture: yield more small mollusks can be done farmland fertilizer or feed, for example, produced by the Chinese coastal the find's muscle clams, the duckbill clams, basket clams can be pigs, ducks, fish, shrimp, freshwater production escargot Corbicula fluminea breeding freshwater fish. Industrial value: mollusc shells is a good raw material for lime, east, south along the coast over the many shells burning lime kiln, part of the source of lime for building. The thick nacre shells (such as clam, trochus, etc.) Buttons of the raw materials. 5, process value or decoration value: Many shellfish shells unique shape and pattern, shiny, colorful, various baby, Conus, conch, ladder snail murex, scallops, sea daisy clams, pearl, etc. Chinese and foreign people like to collect enjoying the product. Some shellfish, such as mussels, mussels, abalone, Don crown, melon snail production inlaid, shell carving, and arts and crafts materials. 6, geoscience value: mollusks in the geological history many as an indicator of depositional environment refers to the relative fossils. In the world and the very bottom of the Cambrian, more than the veneer Gang and other fossil mollusks, many of the Mesozoic ammonoids intercontinental range division and correlation of strata with fossil, and some can be used to understand the ancient waters temperature and salinity; mollusk fossils reflect the Quaternary climatic environment. Harmful aspects of 1, harm to agriculture: terrestrial snails, slugs eat plants, leaves, buds, some carnivorous species in the marine hazards vegetables, fruit, tobacco, etc.; jade snail, lychee Lo, Rhodospirillum can kill oysters, mud cockles seedlings, resulting in the loss of breeding Lamellibranchia; eat kelp, seaweed seedlings herbivorous species (such as teeth Lo, rust concave snail, Aplysia, etc.), is the predators of algae farming. 2, human, animal infectious diseases medium: in freshwater and terrestrial molluscs, there are some types of infectious diseases of humans or livestock media, such as Lymnaea, the intermediate host of Fasciola hepatica beans Lo China branches intermediate host of C. sinensis, flat volumes Lo is the intermediate host of the Fasciolopsis semisulcatus curled is the intermediate host of paragonimiasis of snail intermediate host of Schistosoma japonicum, very serious harm to humans. Harbour construction and transportation hazards: shipworm ocean, sea bamboo is dedicated Farfetched caveman type of wood or rock, wood, stone building wooden boat in the ocean, the stakes and the harbor has hazards. Shipworm especially, of ocean timber hazards are very serious. The battalion attached or sessile species (such as mussels, oysters, etc.) is often a large number attached to the bottom of the boat, and can affect the speed of vessels. Some of them attached to the kind of life (such as ornaments shellfish, mussels, marsh clams) living in the cities along the coast, Lake plant cooling water pipe system can clog water pipes, affecting production.
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The Mollusca (fossil)
软体动物门（化石）
ruanti dongwu men (huashi) The Mollusca (fossil) Mollusca vertebrates door, both aquatic and terrestrial species, the most abundant species of Marine Biology, habits vary, there are many as indicating the depositional environment relative to fossil. In the world and the very bottom of the Cambrian, the existing veneer Gang and other fossil mollusks, the more important position in more new formation. In addition to the classification evolution also marked the formation era, as many Mesozoic ammonoids become divided intercontinental range, contrast formations with fossils, and some can be used to understand the ancient waters of temperature, salinity, etc.; snail fossil energy reflect Quaternary climate and environment, but also can be used the carbon isotopic age determination as well as the study of biological rhythms, to learn the ancient cycle of the Earth's rotation; the Quaternary fossil Sometimes with archaeological significance; certain fossils, such as the Bivalvia solidified the distribution of genera and species of clams favor of continental drift and plate tectonics. Overview mollusks key link between the different and difficult to find a common structural feature can only be based on the morphological characteristics of the gradient, embryogenesis approximation as well as fossil evidence of the evolution of the history of each other, unified mollusks door. Mollusks, in addition to the original without board, veneer and outside the board outline, Ceratocystis Gang of single shell in the back of the central fold for the two, but both how many are connected, and that only the growth of a common origin. Lower-level representatives of the back junction calcareous shell pieces connected to the beak of a rear shell; representatives of higher development. Bivalvia may be evolved by the original Ceratocystis Gang, the junction of the back the calcareous shell into horny ligament, the head also more degradation. The majority of species of gastropods nearly cone deepened by the single-shell, visceral mass of the animal to reverse the spiral casing also rotate into. Dig foot outline may Ceratocystis Gang evolved its single hull the abdomen wrapped and healing pyramidal shell, wrap stretched animal. Cephalopods in the door most hair Dart, extremely well developed head foot turned tentacles, straight shell wrist and funnel casing shells, the bow shell ring shell and spin shell type, the inner shell shells package for the software volume, or even shell degradation. Fossil Bivalvia of the door and brachiopod should be distinction Limao like hingeless brachiopods, as far as muscle scars, single hull or double hull, with or without pedicle pore shell and material composition, with the door veneer Gang Gastropoda Li Mao-like fossil distinguish. Arthropoda conchostracans fossil shell chitin and membranous shell valves growth bring various subtle shell ornaments, fine growth lines, regular, non-disruptive, bifurcate, intersect or pinchout phenomenon, with the distinction door Bivalvia fossil. Most mollusks habitat in shallow water, and is also found in the intertidal zone and the deep sea of thousand meters deep. Bivalves and gastropods can live in fresh water, which there are terrestrial species. Many types of solid Bivalvia clams and cephalopods Nautilus class as a sign of warm seas, some snail fossils reflects terrestrial climate. Or near the polar regions in the north temperate the freshwater mollusks autumn winter drill into the mud and moved into deep water area; arid areas and deserts, they also penetrate into the mud latent ranking, some snails class mucus secretion in the desert, the self-styled Yanxi buried firmly attached to the tree trunks and rocks, rain, recovery gluttonous big food. Therefore, the larger value indicate paleogeographic environment gastropods and bivalves. In addition to the dig cephalopods, other molluscs already in the Cambrian fossil discovery veneer Gang Gastropoda fossils in the Lower Cambrian also found and differentiation, like they have in the Cambrian before may have occurred. No plate Gang whether its imprint fossils exist in the Cambrian or under formation is still uncertain. The Limao like and with bilaterally symmetrical the back muscle scars class (tergomyan) dispersed veneer Gang animal, both extant and fossil representatives of the Cambrian, Cambrian after formation appeared shell higher , the little spin ring and ring or nearly circular muscle scars the muscle scars class (cyclomyan) veneer Gang fossils. Latter in the progress of the species, still being investigated. Multi-plate Gang fossils found in the Upper Cambrian. Weaker the overlaying among the the Paleozoic fossil majority of plates and shells, such multi-plate class is still a case of lifetime so far; Mesozoic multi-plate Gang of fossil more detailed understanding of evolution. The elongation of the body from the multi-plate type, dorsal ventral overlap, it was nearly flat and multi-shell multi-plate the Gang may adapt to curl with rugged underwater life in the shallow intertidal. The board class veneer class and multi-board class than those of the original, these three categories are Trochophore without veliger stage, may be from
Bivalvia