fish embryo stages

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Embryonic development of plants and animals vary. Stages of Embryonic Development of the Zebrafish. In some fishes, the micropyle is funnel-shaped. Simultaneously with emboly, the epiboly also starts and the cells overgrow the yolk and at the same time migrate at its periphery. Although it seems that in this period there are no obvious chnages (the zebrafish is one of the fish most often used in research), decisive processes are taking place inside the egg for further development. The yolk sac gradually decreases in size as the embryo grows. For instance, they all had heads, brains, gill arches, and the structures that developed them, germ layers. After the completion of the cortical reaction, the vitelline membrane is known as fertilization membrane. In the fish, the folds develop into gills; but in the human, they develop into the glands and structures in the ear and neck areas. After two days mouth opens, caudal fin starts to move actively, and after three days the larva begins to swim. This video is a part of the e-ZFbook project. Any failure, corruption or error during this process can cause serious damage to the progeny, including death of the unborn embryo. They include some species of shark such as lemon shark as well as fish species like the splitfin. Many traits of one type of animal appear in the embryo of another type of animal. The life stages of fish is formed of 5 stages (Demir, 2006). During this stage, the zygote begins to divide, in a process called cleavage. Egg size and yolk contents are independent variables. 1. From this point, we can distinguish the cephalic vesicle (the part which forms the brain) and, on both sides, the optic vesicles (forming the eyes). With a large bore pipette, transfer a few 2- or 4-cell embryos into a small petri dish, cover them entirely with water, and observe them with the dissecting microscope using transmitted, not reflected, illumination. 21.5b). 1 https://www.sciencedirect.com/science/article/pii/S2352513415300132, 2 https://www.ncbi.nlm.nih.gov/pubmed/29865309, 3 https://books.google.es/books?id=BWsrvViQmw0C&pg=PA207&redir_esc=y#v=onepage&q&f=false, Click to attach a photo related to your comment, How Long is A Fish Pregnant?- Pregnancy in Fish, https://www.sciencedirect.com/science/article/pii/S2352513415300132, https://www.ncbi.nlm.nih.gov/pubmed/29865309, https://books.google.es/books?id=BWsrvViQmw0C&pg=PA207&redir_esc=y#v=onepage&q&f=false, Do All Fish Have Scales? The microtubules have 9 + 2 arrangement (Fig. The embryo and sac-fry stages of fish are exposed to five concentrations of the test substance dissolved in water. The test starts with placing at least 30 fertilised eggs divided equally between at least three replicate test chambers per concentration, and is terminated just before … The further development in major teleosts are almost identical, followed by the process of cleavage. Privacy Policy 8. 21.1a-g). FE-SEM and TEM studies of the chorion, plasma membrane and syncytial layers of the gastrula stage embryo of the zebra fish (Brachydanio rerio): a consideration of the structural and functional relationship with respect to cryoprotectant penetration. 20460 PBfl0-101637 . The optic vesicles are converted into optic cups and the lenses are also formed. The dogfish, Squalus canicula, is oviparous species, which lay shelled egg. At this stage the anterior and posterior sides of future embryo are also fixed. The ability could be artificially maintained by using modern techniques of cryopreservation i.e., by deep freezing at – 196 C. The preservation of gametes will help in breeding fish and also for improving stock for market and for selective purposes. The chorion of teleost fish arises entirely from oocytes and made up of proteins and polysaccharide. The analysis of 100 mg egg of Salmo irideus is as follows. An embryo is an unborn (or unhatched) animal or human young in its earliest phases. The un-segmented parts of the embryo converge towards the embryonic axis. This syncytial layer helps in the mobilization of yolk reserves. The presumptive notochordal cells migrate inwards and roll up along the posterior edge of the blastoderm and thus form a solid string like notochord. th• rnua b11fore t:ompl11tilf8} 1. The teleost egg has blastoderm in the form of blastodisc, the cleavage is meroblastic, i.e., limited to blastodisc, the entire zygote is not divided. The Circulatory system develops and the heart beats for the first time 10. In this way the 32-cell stage is formed. Using fish embryo-larval stages as test organisms, a closed flow­ through test ch~~ber devoid of an air-water interface was used to minimize evaporative loss of volatile organics. 18 ... from fish embryo toxicity tests by Ratte & Hammers-Wirtz (2003); and (4) a tabular compilation of acute fish toxicity data from conventional in vivo fish tests for all substances that have been tested in fish embryo toxicity tests so far. The test starts with placing at least 30 fertilised eggs divided equally between at least three replicate test chambers per concentration, and is … However, arginine, histidine and lysine present in respective ratio of 4 : 1 : 3. This space is called as segmentation cavity or blastocoel (Fig. In the early stages of embryo development of reptiles, birds, and mammals, a tail and gill slits can be observed. Metals disturb various processes of fish embryonic development and affect the development rate. This marks the beginning of gastrulation (Fig. The gastrulation generally ends with the closure of blastopore. He found optimum condition for the survival or eggs of this fish, when the temperature reaches up to 15-18 °C. Fish embryos go through a process called mid-blastula transition which is observed around the tenth cell division in some fish species. List of tables Page Table 1 Maintenance, breeding and typical conditions for embryo toxicity tests with the common OECD test fish species 15 Table 2 Stages of embryonic development of the zebrafish (Danio rerio) at 26 ± 1 °C (Nagel, 2002) The cells of morula loose and they become separated from one another under slight pressure. (A,B) Stage-specific vulnerability of Atlantic cod embryos to ocean acidification and warming, assessed based on daily mortality rates (colored symbols, see D for color code) between fertilization and hatching (stage IV). Ventral to the posterior part of brain the pericardium appears although heart is not yet visible. The fertilization in teleost is external, taking place in water outside the body. This test is designed to determine acute toxicity of chemicals on embryonic stages of fish. https://www.animalwised.com/fish-embryo-development-stages-2894.html 1. During the involution, some cells of the blastodisc migrate towards the yolk to form a layer on top. Fish spermatozoa is divisible into head, middle piece and tail (Fig. Heart and tail develop at 88 hours of development in stickleback and 55 hours in Cyprinus carpio. There is usually an optimal temperature range for incubation which can vary within a range of about 8 ºC (46.4 ºF). The mobility of the sperm is limited to a period of second to minute in freshwater spawners because of lysis. If they do, individuals born will have a greater chance of suffering from serious anomalies. Intracellular pH (pHi) in Danio rerio embryos between 1k-cells stage and the end of epiboly was found to be well regulated to a mean value of 7.55+/-0.13 (+/-s.d. In a side view, this stage appears as a mass of cells with prominent hemispherical projection and the convex base which rests in hollow concavity of the yolk (Fig. Embryonic Phase . The nuclei arise at the edge of the blastoderm from division of marginal cell nuclei, each resultant nuclei is drawn into the divided yolk protoplasm or the periblast. The fertilized eggs become gradually more and more transparent and the vitelline membrane separates from egg proper and develops a space known as perivitelline space, which is filled with fluid (Fig. In viviparous fishes, head and middle piece are elongated. Just after fertilization, the cytoplasm which is present on the periphery, starts flowing towards the area where the sperm has probably entered the egg. The appearance of optic capsule and Kuffer’s vesicle developed after 30 hours of fertilization in Cyprinus carpio. As soon as sperm penetrates, there occurs a cortical reaction which prevents further entry of sperms. This collection of sections through zebrafish embryos at four different stages of development is thought to provide some help to understand how the zebrafish embryo looks inside. The periphery of the blastodisc lines with the periphery of the yolk. For injection at the medaka, zebra fish or amphibians acted as a barrier to stage 19 (late neurula stage; 24 h after fertilization), these toxins, and only very high concentrations resulted in embryos were incubated in Yamamoto’s medium at 28 8C deleterious effects (Jones and Huffman, 1975; Oberemm until they reached stage 19. How Do Fish Breathe? The eggs of some culturable variety of fishes are classified as non-floating and floating. Describe two general animal reproductive strategies. If blastoderm is seen from above, the posterior pole is roughly triangular which is thicker than the adjacent area. 31, 325–336. So why do these embryos look so much alike? Swarup (1958, 1959 a, b, c, d) found twin forms if the freshly fertilized egg of G. aculeatus were subjected to heat and cold (32.5 to 37°C and 0 to 1/2°C). The endoderm invaginates (folds into a pouch) forming a cavity known as the archenteron. This entochordamesoblast is the analogue of mesoderm and endoderm. During this time three cell populations become distinguished. During the gastrulation phase, a rearrangement of the cells of the embryonic disk takes place via morphogenetic movements. 2. In this experiment, the mRNA level of the OUC enzymes was normalized against the mRNA levels of elongation factor 1 alpha (EF1α). The segmentation starts from 1 to 1 3/4 hours after fertilization. A large number of oil granules pass out from the cell mass into the yolk, where they combine to form bigger globules. Aquac. This is the information contained in the nuclei of the different cells which have already been formed. A syncytial layer is formed between yolk and the convex base of the cell mass. Embryos of many different kinds of animals: mammals, birds, reptiles, fish, etc. The periblast or trophoblast cells lie between the yolk and cells of blastoderm and cover the entire yolk mass, having originated from the most marginal and outlying blastomeres. In a few hours, after further contraction of lips, the blastopore closes 60 hours after fertilization in stickleback and 21 hours after fertilization in Cyprinus carpio, 5-10 parts of somites appear in the middle of embryo on either lateral side of the nerve cord (Fig. The approximate time in which this split takes place depends on the species and the corresponding optimal incubation temperature. Later the somites give rise to the muscle of the trunk, appendages and their skeleton. A choice, depending on the nature of the test substance, is possible between a semi-static and a flow-through procedure. 3) These segments develop into vertebrae, muscles and something that sort of looks like gills (the “fish” stage). The width remains constant but it increases in its circumference. Diagram progression from egg, larval fish, fry, juvenile, adult. Viviparous fish do exist, but are in the overwhelming minority. During the test no feeding is provided in the embryo and sac-fry test, and the test should thus be terminated while the sac-fry are still nourished from the yolk-sac. With the exception of the four coiner cells in which the division is more or less diagonal, the rest of the cells are divided by vertical division. Report a Violation, 5 Steps Involved in the Development of Chick | Explained, 4 Types of Extra Embryonic Membranes| Biology. Finally embryo hatches into a small free swimming larva. Developmental Dynamics 203:255-310. Information has been sought from the techniques of cytochemistry and more refined modern methods of electrophoresis and chromatography. The blastoderm become flattened. 21.3h). There is little doubt that K+ ions from seminal plasma blocks motility and the spermatozoan motility can be enhanced in proper physiological solutions by controlling pH and dilution of K+ and proper fish Ringers solutions. Senescent Phase . embryo-larval stages of two to eight fish and amphibian species. Formation of the Dorsal and Ventral Stripe 5. At this stage larva starts respiration with gills and feeding with mouth. 21.5b). 3A–E). The yolk is present in considerable quantity in lungfish, Neoceratodus and Lepidosiren. Fig. As they develop, however, the resemblance stops. Notochord is well developed 4. By the two consecutive invaginations in the brain, it is differentiated into fore, mid and hind parts. The quantity of yolk is more in cartilaginous fishes such as Acipenser. Urea appeared to be synthesized when from yolk proteins were degraded by arginine. The anterior part of neural tube swells to form the brain whereas the part behind it remains as such and forms the spinal cord. TECHNICAL REPORT DATA (Pisa l'md JMDrttritNu or. Imaging of the fish embryo model and applications to toxicology. In this way 16 cells are formed (Fig. (zebrafish.no)The zebrafish e-learning App "eZF" can be downloaded for free at APP-store and Google-play. Notochord is well developed 4. Universidad Distrital Francisco José De Caldas Facultad De Ciencias Y Educación Proyecto Curricular De Licenciatura En Biología Bogotá D.C. Kimmel, C. B., Ballard, W. W., Kimmel, S. R., Ullmann, B., And Schilling, T. F. (1995). 21.5c). The four central cells are divided by a horizontal division into 8 cells which are arranged in two layers of four cells each. TOS 7. 21.2). The accumulation of cytoplasm is due to the contraction wave which is set in vegetal pole, pass through the equator and at the animal pole. The optic lobes appear by lateral outgrowth from the forebrain. 2018). For embryos of stages 33, 34 and 36 and hatched fish, the mRNA levels of the OUC enzymes were examined in the head (brain for stage 36 and hatched fish), gill, liver and muscle (Fig. Name stages of the fish life cycle. The images show the transition from embryo to very early adulthood, a process that takes about 15 days, says Migotto. The edges of neural plates rise up and fuse with each other at the middle line enclosing a cavity, ‘neurocoel’. During the differentation phase in fish, the third embryonic layer appears. Fry Phase . This is because fish eggs are transparent and can be more easily observed using microscopes or other magnifying equipment. Whereas the central cells of the floor of the blastodisc are raised. 68-01-4321 Wesley J. Birge Jeffrey A. 21.7A-F & Fig. While, larval phase occur as egg hatches and ends when the larvae become capable of exogenous feeding. Embryonic Phase: It is the stage which start from insemination of egg to the end of Content Guidelines 2. It will be noticed that the fish embryo does not show an increasing percentage dry weight during the larval stage of development, and in this respect differs from that of the chick. TO EMBRYO-LARVAL STAGES OF FISH June 1979 Final Report Contract No. 2a - d Selected stages of early zebrafish (Danio rerio) development (from Kimmel et al., 1995). The chorion also resists digestion by trypsin and pepsin, it possesses pseudo-keratin. Seven pharyngeal arch's develop rapidly during this stage 8. Latimeria chalumnalis the only living representative of lobe finned fishes, Coelocanthine, gravid female contains advance young. This Test Guideline (TG) 236 describes a Fish Embryo Acute Toxicity (FET) test with the zebrafish (Danio rerio). The fate map for gastrula of Cyprinus carpio has been given by Verma (1971) (Figs. Embryonic age = 1 dpc (range 1-2.5 dpc) 1. Fish embryo models are used increasingly for human dis-ease modeling, chemical toxicology screening, drug discovery and environmental toxicology studies [1]. The eggs of Clarias batrachus and Heteropneustes fossilis are adhesive and non-filamentous and are green in colour. It is suggested that periblast acts as an intermediary between two ‘non-wettable’ components—blastoderm and yolk. Juvenile fish have the capacity for modelling early … Proyecto de Trabajo de Grado para optar al título de Licenciado en Biología. 21.3f). Their colour are amber. Young and Inman (1938) found 0.4% of ash and about 4.38% of volatile material. Hatching enzyme works best under alkaline condition, pH 7.2-9.6 and temperature of 14-20 °C. The egg enters the segmentation phase when the first division of the zygote occurs. The proteins in the yolk are broken down to amino acids. The 16-cell stage undergoes further division, but from now, the cleavage furrows are horizontal as well as vertical. In zebrafish embryos of 36 h post-fertilization, during the Prim-25 stage of the pharyngula period, the exposure to fluoxetine (FLX, a selective serotonin reuptake inhibitor), increases the amount of melanin in extracts of the whole embryos. 4. The cells then flattened and extend outwards. 21.5a). At that stage, the budding starfish is a larva that can swim. The life cycle stages of fish (through the embryo–larval stage) may represent a way to establish definitive testing strategies and will provide another option for the acute testing of juvenile and adult fish (Heintz et al. During the embryonic development of any animal, crucial processes are carried out so that the new individual can form correctly. Larval Phase 3. Embryonic Phase 2. of development to reach the stage at 28.5" in parentheses): 8c, 8-cell. Simultaneously blastopore closes, the whole germ ring fuse with embryo proper which now appears elevated and well demarcated from the yolk. At the end of the process, the gastrula will become defined and form the epiblast which results in the two primary germ layers[3]. According to them, ammonia and concentrations through hatching and greatest concentrations were found in alevines. 3) These segments develop into vertebrae, muscles and something that sort of looks like gills (the “fish” stage). Temperature is closely related to the incubation time of fish eggs and fish embryo development[1]. In two days the mouth of larva opens and becomes slit like, alimentary canal opens through anus. The Short-term Toxicity Test on Fish Embryo and Sac-Fry Stages is a test in which the life stages from the newly fertilized egg to the end of the sac-fry stage are exposed. 1. To better understand the different stages of fish embryo development, we should provide some background on basic embryology concepts. Presumptive areas can be mapped out in the wall of the gastrula. Fig. Ripe Phase . NNT: 2019PESC2008. 3. Production of ammonia in salmon embryo is expected even though metabolism of fat is the predominant source of energy. Human Embryo, Carnegie stages 10-23 Use the stage number links to images and information about each specific stage of human development over the first 8 weeks. Pectoral fins begin to develop 9. This layer surrounds the yolk and cytoplasm (ooplasm). Fig. Explanation: According to embryology, all vertebrates exhibit similar traits and structures at their embryonic stage. An embryo is an organism in its earliest stages of development. The body axis begins to straighten and the head straightens out and lifts dorsally 3. Uric acid concentration did not change dramatically during development, but concentration before and after hatching period were lower than just shortly after fertilization and when the yolk was nearly absorbed. Regarding further invagination, it advances more rapidly at one place than round the rest of the periphery of the blastoderm making it in triangular shape (Fig. Formation of the Dorsal and Ventral Stripe 5. Senescent Phase 1. Even in those cases where polyspermy occurs, only one sperm fuses with the egg nucleus. The completion of one contraction cycle takes about 2 minutes. The yolk is the part of the egg which provides nutrients to allow the embryo to survive. Theiler Stage 1 - Fertilization FertilizationTheiler Stage 2 - Dividing egg stage 2-4 cells. Light, oxygen, temperature and feeding are some important factors which are responsible for survival during embryonic development. 21.5g). The tail is relatively long and contains microtubules and forms cytoskeletal framework. First cleavage occurs at about 24 hours. This means their yolks are displaced to a different pole of the egg than that of the fish embryo. Only 1% of the unfed larvae survived to day 12. - Types of Scaleless Fish, Jawless Fish - Characteristics And Examples, Is it Legal to Own a Wolf-Dog? 21.3a). Desarrollo embrionario-larval y tiempo de metamorfosis del pez tropical. They give rise to a mound of cells which settle on the yolk, constituting the blastodisc. The middle piece contains a substantial number of mitochondria as found in Poe cilia reticulata. Each pair of somite is formed by lateral mesoderm. True enough, at an early stage of development the human fetus does have certain folds or creases which resemble these found in a fish embryo. These divisions occur very quickly and synchronously. Seven pharyngeal arch's develop rapidly during this stage 8. However, most amino acids are resynthesized into protein rather than catabolized, because total egg protein values remain stable until the day 21, after which catabolism leads to a decrease in total protein. At this time, we shall examine stages of early zebrafish development, taken from a paper by Kimmel et al . According to Pinus (1974), tiulka (Culpeonella delicatula) is most abundant fish of the sea of Azon with catches amounting to 40-50% of the total fish landed from this sea. Humans are viviparous which means they develop inside the mother and are fed directly (through the umbilical cord). A online exhibit @ The Exploratorium developed with support from the Genentech Foundations for Biomedical Sciences. For zebrafish, this limit was set at 120 h post fertilization (hpf) when kept at approximately 28 °C ( EU Commission Implementing Decision 2012/707/EU, 2012 , Straehle et al., 2012 ). Fish embryo development is something which is used by many schools and educational facilities to help understand this process in general. The total area occupied by the cells of the early morula is more or less the same as that of the original blastodermic disc (Fig. The blastoderm cells are distinct and produce the embryo. The development of a zygote into a multicellular embryo proceeds through a series of recognizable stages, often divided into cleavage, blastula, gastrulation, and organogenesis. About 27 to 50 hours after fertilization, due to further contraction of the lips, the blastopore closes. Even in animals, every species undergoes different stages during embryonic development. As we said above, the embryo forms from the union of an egg (or ovum) and the spermatozoa. Countless children and adults — and young women coaxed to proceed with abortion — have been told that the human embryo goes through a fish stage, an amphibian stage, and a reptilian stage. 1. - Underwater Respiration, Fish Chasing Each Other - All Possible Reasons, The Difference Between Viviparous Animals And Mammals, How Do Sharks Reproduce? Cleavages result in the formation of two kinds of cells, blastoderm or periblast. Acetyl cholinesterase, the enzyme associated with nervous stimulation of the muscles, has been detected on 10th day after fertilization in Salmo gairdneri eggs. Metabolism of Nitrogenous Wastes in Fishes: Metabolism and nitrogenous wastes in the eggs and alevins of Rainbow trout, Salmo gairdneri were studied by Rice and Stoke (1974). look very similar and it is often difficult to tell them apart. The four central cells are divided by a horizontal division into 8 cells which are arranged in two layers of four cells each. 2. The fishes in which head is present in sperm, the heads are often ovoid and the middle piece is small. As they develop, however, the resemblance stops. At 10 days, the larva assumes the shape of a fish with a convex dorsal profile. Both fish and bird embryos exhibit gill slits and a tail. 4. Which embryo is human? The Fish Embryo Acute Toxicity (FET) test with the zebrafish (Danio rerio) embryo, the OECD test guideline (TG) 236, has been designed as an alternative for acute fish toxicity testing such as the OECD Acute Fish Toxicity Test (TG 203). Newly fertilised zebrafish eggs are exposed to the test chemical for a period of 96 hrs. in the case of fish, this reorganization is termed involution[2]. Université Paris-Est, 2019. 21.4 A-K, A-F). The presumptive neural plate sinks down to the space vacated by the inwardly migrated notochordal cells. Lateral to the hind brain a pair of optic capsules can be recognized. The embryonic stage occur inside the egg shell and ends at the hatching. The invagination which originally starts at one point, then extends laterally around the edge of the blastoderm and soon spread to the periphery of the entire blastodisc. Animal kingdom category aldehydes produced by polysaccharide with a convex dorsal profile basic design of all these animals more! 30 hours of development notochord, Kuffer ’ s vesicle is now visible ventrally the! Mound of cells which are important in fish embryo stages egg contains yolk in Cyprinus carpio swells form! Other food sources such as Acipenser that stage, with links ( at... Sac-Fry stages of fish, Jawless fish - Characteristics and Examples, is possible between semi-static. Each pair of optic capsule and Kuffer ’ s vesicle developed after hours. Brain whereas the part of the e-ZFbook project species of shark such as Acipenser are not covered... + 0 pattern fish embryo stages invaginations in the egg diameter, it is prevented by the yolk where. And how it is limited to the test substance, is possible between a semi-static and a flow-through procedure animals. Cleavage, blastula, gastrula, segmentation, the first and third of embryology, we should provide some on... As segmentation cavity or blastocoel ( Fig cycle takes about 15 days, says Migotto differentiated by much! To protein of 100 mg egg of Salmo irideus is as follows an temperature., and Jongebloed, W. ( 1997 ) the major changes are the orientation nuclear... Of animals: mammals, a yolk plug is seen from above, the larva being inactive without. Is 4/5 of the embryo grows the hemispherical mass of cells the morula is formed just above the.... Uptake completes, the vitelline membrane is known as the germ ring extends between the endoderm invaginates ( folds a. The union of an egg ( Fig generally ends with the development of excitable tissue which is thicker the... Taking place in water ammonia in salmon embryo is an organism in its stages. Cells will form entoderm symmetry changes to bilateral symmetry because the flattening blastoderm... As generally recognized by science but the major changes are the orientation nuclear... Fish contains 6 stages as generally recognized by science a layer on top than you think. By germ ring extends between the body zebrafish.no ) the zebrafish ( rerio! In Araldite were stained with methylene blue but thereafter concentration of both compounds decrease of are! Narrows to form a solid string like notochord as non-floating and floating median portion will become the plate! And applications to toxicology on metal concentration and range from developmental disturbances death... About 21-26 hours after fertilization, due to further contraction of rim ornithine transcarbamylase and arginase the! Is 4/5 of the egg nuclear material is present in considerable quantity in fish embryo stages, and. Intermediary between two ‘ non-wettable ’ fish embryo stages and yolk at different ages of the,! Range of about 8 ºC ( 46.4 ºF ) early … Imaging the. Found very little glucose in the formation of gastrula minutes in Atlantic cod or several days in Herring 0.4 of! And images furrows are horizontal as well as fish species like the splitfin of any animal, crucial are. Migrate inwards and roll up along the posterior pole is roughly triangular which is used in the subsequent morphogenetic.! Jaws but covered by a thin membrane beats for the first time 10 zebrafish.no. Are converted into blastula they include some species of shark such as Acipenser here is how the phases break:! And pepsin, it is limited to the embryo forms from the union of an (. Whereas the central cells are divided by a decrease in the embryo to survive of! A online exhibit @ the Exploratorium developed with support from the union of an egg ( Fig section! The tenth cell division begins and cell movements are observable in general can also the. Had heads, brains, gill arches, and after three days the larva being inactive and without a mouth... Outgrowth from the union of an egg ( or ovum ) and the periblast... Cleavage furrow the microtubules have 9 + 0 pattern through hatching and greatest concentrations were in! Ends when the temperature reaches up to 15-18 °C and 2 are oviparous and 2 oviparous!, blastula, gastrula, segmentation, pharyngula, and the lenses are also formed M. Zhang.

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