Lanzhou wolfberry, which belongs to the order of Oystercatcherus, Amaranthidae, and Oystercatcher, commonly known as the Yellow River Slug, is an indigenous large-scale carnivorous wild economic fish in the upper and middle reaches of the Yellow River. It has high nutritional value and is commonly known as the Yellow River Eel live ginseng [1]. Due to the environmental pollution and overfishing of the Yellow River in the latter half of the last century, the resources of the fish have been basically depleted and were incorporated into the “Red Book of Endangered Animals (Fish) in Chinaâ€[2]. With the in-depth development of the protection of indigenous fish resources in the Yellow River, the artificial breeding of Lanzhou pupa has been successful [3]. In this paper, observations were made on the development of larvae and juveniles in Lanzhou. The morphological characteristics of the developmental stages were described. The aim was to enrich the biological data of the early development of the Lanzhou crucian carp and to improve the artificial propagation of the seedlings in Lanzhou. The seedlings provide technical basis for the cultivation of technical processes and raising the breeding level of seedlings. Materials and methods The experimental materials were taken from the artificial fry, natural spawning fertilized hatching fry (incubation temperature 24 °C -25.5 °C, fertilized eggs hatched out of larvae after 39h37min). The larval stage and the juvenile stage are kept in an indoor aquarium and the water is changed daily (aeration tap water is mixed with filter water) once, and the dirt is removed and fed. During the larvae period, the cooked egg yolks, horns, and filaments were fed and the juveniles were fed with silkworms. Freshly hatched larvae are observed once every 2-3 hours, and once every 24 hours after 24 hours. Each time, 10 fishes were randomly selected from the aquarium, lightly anesthetized with 10% alcohol, observed under a Motic stereomicroscope, and photographed. The total length, the length of the anus, and the length of the anus were measured, and the changes in the external shape were recorded and anatomized. , Observe the development of internal organs; record the time of this period when more than half of the sampled individuals reach a certain level of development. At the same time, fixed part of the specimen in 5% formaldehyde solution for verification. The water temperature of juvenile development varies from 22-26°C. The division of developmental stages and periods of juveniles is based on the study of the development of juveniles of beard pupa[4] and southern big gulu[5]. According to the changes in the external morphology of juvenile juvenile larvae, establishment of internal organs and activity habits, they are divided into pre-larvae, The larval stage and the juvenile stage three stages. For ease of description, several periods are subdivided according to developmental characteristics. Results 1. Pre-larvae. At this stage, hatching from the larvae to the yolk sac, most of the larvae were absorbed and the juveniles began to ingest external nutrition until 5-6 days. Newly hatched larvae: freshly hatched larvae, total length 5.1-6.3mm, 2.5-2.9mm long after anal, 44-47 pairs of body segments; yolk sac large, nearly round, 1.5-2.11.3-1.9mm . Body pale yellow, slightly curved back, head on the yolk sac, bent at the end of the tail. The maxillae must be primordial, broadly paddle-shaped, slightly protruding from the front of the head; the olfactory sac is clear, the eye sacculus is rounded, and the eyes are grayish; the ear cysts are slightly longer and are located on both sides of the embryo body just above the yolk sac; Flaky, located behind the maxillary sulcus, below the ear capsule, below the ear capsule zygomatic arch base; yolk sac and embryonic body with a oval-shaped pectoral primordium. The peritoneal cavity is wide and the heart with red blood can be seen through the peritoneal membrane. The heart rate is about 115 beats per minute. The intestines and anus have been differentiated, the posterior side of the body is flat, the fins are narrow and thin, and they are integrated (Figure 1). After incubation for 5 hours, the digestive tract was clear and clear, and the anogenital primordium differentiation was obvious. Just shed larvae like clusters, heads close together. Its athletic ability is not strong. By relying on the non-stop movement of the tail, it seldom swims on the water surface. When it is shaken, it swims to the upper middle and then quickly sinks vertically and rests on the attachment. Pigment appearance: larvae 9 hours after filming, 48 pairs of body segments. Mouth cavities appear, pigments appear on the back of the eyeball and in the cysts, and there are relatively more pigments on the head. Protrusions appear under the lid, the first pair of jaw whiskers. The lobular pectoral primordium appears posterior to the zygomatic arch, which lies on the dorsal side of the yolk sac; the primordium of the caudal fin appears. The posterior end of the yolk sac narrows and appears egg-shaped; the Vieux tube in the front of the yolk sac appears red.鳃 blood circulation: 18h after filming, full-length 6.0-6.7mm, 49 pairs of body segments. Three parallel gingival sulcuses appear, the first of which is relatively clear. This is the beginning of the zygomatic arch; blood flow is visible. The edge of the olfactory sac protrudes, and the middle depression; The zygomatic cap primordium is tilted upwards from the yolk sac to expand and cover the lower part of the first sulcus. The second jaw whisker appears as a protrusion behind the first jaw whisker. The jaw appears and the mouth is noticeable. The yolk sac is oval in shape. Eye pigmentation increased and deepened, and the fish eye became darker with the naked eye; body surface pigmentation increased (Figure 2). The larvae are sensitive to light, and under intense light stimulation, the systemic activity accelerates and flees. Mandibular active period: larvae 36-40 h after filming, 6.5-7.5mm in length, 3.6-4.2mm in length after anal, and 59 pairs in somite. The lower jaw starts to move but the upper and lower jaws cannot be fully closed. The pigment at the top of the head is densely meshed. Bow extension, 4 pairs. The posterior edge of the zygomatic arch has a dentate protuberance, which is the silk primordial; the zygomatic lid has covered most of the arch, leaving only the posterior half of the last arch exposed. The yolk of the yolk sac is absorbed and a small space appears. The nasal sac was rounded; the front and rear ends of the ear capsule projected upwards and a semicircular canal occurred (Figure 3). Gastric differentiation: 66-70 hours after the membrane, 66 segments, 6.9-8.0 mm in length, and 3.8-4.4 mm in length after the anus. The mandibular movement is frequent, and the fins of the caudal fins appear as fins. The width of each odd fin pleat increases slightly, and it is still connected to one piece. The foregut begins to differentiate into the oropharyngeal cavity and esophagus; the yolk in the upper part of the yolk sac is absorbed and a space appears. It can be seen that the middle intestine enlarges between the stomach and the intestine. The end of the hind intestine is merged with the anal canal formed by the inward depression of the anal indentation. Further penetrated into the anus. The lid covers the entire zygomatic arch and covers the front of the yolk; the zygomatic arch is more pronounced. The sacral canal that protrudes from the dorsal side of the digestive tract has expanded and is not axillary (Figure 4). The jaws of the fry have rhythmic opening and closing movements. The phenomenon of directional movement of fish fry on the bottom of the water is not obvious, and it can avoid the disturbance. There is a short-term, migratory migration, but it cannot stay in the water layer. 4-5d after filming: larvae are 7.2-8.6mm in length and 4.1-4.9mm in length after anal. Formation of humeral caps, free aponeurosis and opening and closing activities with iliac lids; nostrils are oblong; jaws gradually approaching maxillary length; each should be short-barreled, with kisses, maxillary spurs, and first chin on the leading edge. Perceptive process; pectoral fins differentiate into thick stalks and wide fin membranes. More than 3/5 of the yolk in the upper part of the yolk sac are absorbed; the stomach enlarges significantly, and the stomach occupies most of the space of the yolk sac; the oblate hepatic process appears in the anterior lower part of the yolk sac and gradually expands in front of the stomach; Gastrointestinal walls have folds; the digestive tract has been basically penetrated, and the stomach is constantly moving (Figure 5, Figure 6). Artificially fed yellow rotifers or rotifers and small branches can be fed artificially. Yellow-green feces can be seen in the intestines of the digestive tract. Under microscope observation, undigested food residues were found. 5-6d after filming: The larvae have a total length of 9.6-11.2mm and an anal 5.6-6.6mm. The jaws must be stretched up to the posterior edge of the lid. A small, ridge-like protrusion should appear on the posterior edge of the lid. The position of the pectoral fins should move downwards. The back of the odd-fin fins at the back of the jaws should be recessed to differentiate the dorsal fin primordium; The head is large and the pigments are densely colored with dark spots. Most of the yolk is absorbed, leaving only a small amount at the bottom of the abdominal cavity; the digestive tract occupies the entire abdominal cavity. The length of the digestive tract grows, the bowel bends, the stomach enlarges, and the liver extends in strips. The squat increases and is inflated (Figure 7). Peptic diets are ingested and feces are excreted in the intestines. At this point, larvae have shifted from a complete endogenous nutrition stage to a mixed nutrition stage where both internal and exogenous nutrients are concurrently produced. The formation of dark habits, stimulated by light, will quickly escape from the darkness and be forced to rest in bright places when they dodge without darkness. The larvae are cultivated in artificial waters. The larvae are concentrated in the shade of the water during the day and dispersed in the water during the night to feed on the bait. 2. larval period. The larvae continue to use the yolk material as a nutrient and ingest food from the outside for mixed nutrition. There is a certain difference between body shape and adult body, and the organ differentiation is still incomplete, lasting 6-7 days. 7d after hatching, the total length of 10.4-12.6mm, long after the anus 6.3-7.7mm. The end of the notochord is upturned, and the back of the odd-fin pleats of the back appears concave and differentiates into the caudal fin. After the anus, the odd-fin pleats differentiate into upper and lower parts. The upper part becomes thicker and the lower part becomes the anal primordium. The upper jaw must be longer than the jaws; the surface of the whiskers should have a hedgehog-shaped protrusion, and the front edge is significantly more than the trailing edge. The larvae prefer to feed the silk shrews. After eating, the abdomen is significantly enlarged. The hi stretches the body to lie still. It is often dense at the bottom corner seams, and even the individuals overlap each other and pile up into several layers. 8d after hatching, the total length was 12.2-14.8mm, and the anus was 7.3-8.9mm long. Inflatable, white, shiny, spherical, behind the lid, close to the back of the esophagus. The mid-section of each nostril is brought together to form two round holes that are connected by a ditch, and the front hole has vertical skin folds. Larvae can swim freely in the water layer, but they slowly sink when they are still. 9d after hatching, the full length of 14.4-16.6mm, anus after the length of 8.8.1-2mm. In the lower abdomen of the abdomen, flaky protuberances appear near the fins of the fins, basal pelvic primordiums, depressions at the proximal end of the abdomen and odd fins, caudal fins are initially hatched, obliquely cut, and the rays of the pectoral and caudal fins are formed. There are pigments arranged along the sides of the fins, making the fins clearly visible. After 10 days of incubation, the total length was 15.6-17.8mm, and the length after anal was 9.6-10.9mm. The back of the odd fins of the back was reduced, separated from the dorsal fins, and three fins appeared on the dorsal fin; the fins expanded and differentiated into fins. The maxillary base becomes smooth and pigment appears (Figure 8, Figure 9). The larvae lie calmly after eating during the day; at night, they are active in the entire water layer, and when they are given light, they sink to the bottom of the water immediately. 11-12 days after hatching, the total length was 18.4-21.6 mm, and it was 11.3-13.3 mm long after the anus. All fins are visible: pectoral fins differentiated from pectoral fins, irregular teeth at the posterior edge of the spine, fins I and 10, no branch fins (greater), fins i, 4-5, and pelvic fins. 5 roots; 17 caudal fins; fins in the anterior part of the anal fin are more obvious and difficult to distinguish in the posterior segment. The upper jaw must be long and the two pairs of jaws should be short and approximately equal to each other. The main external organs of larvae are basically differentiated. 3. Juvenile period. Completely ingesting food from the outside for nutrition, organ differentiation, and shape transition to adult form. It lasted 7-10 days. Film 13d, full-length 19.4-24.4mm, long after anal 12.1-15.3mm. The odd fins on the back of the juveniles became significantly shorter, and the fins connected between the caudal fins and the pelvic and anal fins had become very narrow, and the proportion of the long post-anal length had increased (Figure 10). After 15-16 days from the membrane, the total length was 20.7-29.8 mm, and the length after anal was 13.1-18.8 mm. Juveniles have flat or slightly concave tail fins, equal lengths of upper and lower leaves, close to adult fish tails; fin folds from the dorsal fin to the anterior 1/2 of the dorsal fins have disappeared, leaving only a very narrow part of the rest; The former odd fin fold disappeared (Figure 11, Figure 12, Figure 13). After 18-20 days from the membrane, juveniles were 27.3-36.2mm in length and 17.7-23.5mm in length after anal. The odd fins on the back of juveniles disappeared; the fins of each fin ossified. The juveniles that had completed juvenile differentiation were elongated, with a slightly rounded anterior portion and a flattened posterior portion. Except for the presence of a second pair of jaws, the appearance characteristics were similar to those of adults (Figures 14, 15). Swimming ability is enhanced, digestive system is perfect, and predation ability is improved. Discussion 1. At 22°C to 26°C, Lanzhou larvae fish and juveniles develop for a period of about 20 days. The larvae have a total length of 5.1-6.3mm from the time of filming, reaching 27.3-36.2mm. The juvenile period has been relatively long. The long growth of larvae at the anal stage is rapid, and the growth rate is always greater than the length of the body, which accounts for 55-62% of the total body length. After the juvenile stage, the growth of the body length is accelerated, the long growth rate of the anus is slowed down, and the body length is equal to or slightly shorter. Longer than the anus. 2. The development speed of the whisker is very fast. After 2 days of filming, two pairs of jaw whiskers have successively protruded (the jaws must have differentiated before the film is unwound), and the sensory processes on the snout end also form earlier, which is related to its benthic activity. , Underdeveloped vision, depends on the need to help feel that foraging is related to the ability to eat earlier. 3. The larvae of 3-4 days after filming have gradually increased their ability to exercise. They are changed from the recumbent bottom to the benthic group. The depth of the pool is about 60cm. The larvae of 5-6d are active and free. , began to eat outside food, from the complete endogenous nutrition into the mixed nutrition stage, the production should be fed in a timely manner palatable feed, larvae began to feed on the live bait has a natural taste of food, it should be timely switching to live bait. It is advisable to feed artificial bait from this point onwards, and it would be better if it is baited by live baits. 4. The newly hatched larvae did not respond to light. From the 6th day onwards, they developed a significant negative phototaxis. They inhabited in multiple dark spots during the day and dispersed in various places during the evening. Therefore, when cultivating fry, in addition to paying attention to environmental choices, adopting technical measures such as gradually deepening pool water, appropriate shading, or installing artificial shelters at the bottom of the pool will reduce the time of clustering, increase activities and feeding time, and accelerate the development of fry. benefit. 5. From the internal anatomy, the larvae and viscera organ systems have been initially established and have normal functions for 10 days after filming, and the adaptability to the environment has been enhanced. This is also because the yolk material was depleted on 11-l2d, and after 13d, Changes in food intake from the outside world are consistent with changes in nutrition. 6. Juveniles that have completed juvenile differentiation have faster swimming speeds, increased predation ability, gradually weakened colony habits, and there are intra-species rejections that compete for habitat. Therefore, fry breeding should be gradually evacuated or replaced in large bodies of water to reduce the density, prevent hypoxia and bite each other; at the same time, timely evacuation is also an effective measure to suppress the infection and epidemic of fish diseases and improve the survival rate of fish fry. .
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