Segregation of brain and organizer precursors is differentially regulated by Nodal signaling at blastula stage.

The blastula Chordin- and Noggin-expressing (BCNE) center comprises animal-dorsal and marginal-dorsal cells of the amphibian blastula and contains the precursors of the brain and the gastrula organizer. Previous findings suggested that the BCNE behaves as a homogeneous cell population that only depends on nuclear ß-catenin activity but does not require Nodal and later segregates into its descendants during gastrulation. In contrast to previous findings, in this work, we show that the BCNE does not behave as a homogeneous cell population in response to Nodal antagonists. In fact, we found that chordin.1 expression in a marginal subpopulation of notochordal precursors indeed requires Nodal input. We also establish that an animal BCNE subpopulation of cells that express both, chordin.1 and sox2 (a marker of pluripotent neuroectodermal cells), and gives rise to most of the brain, persisted at blastula stage after blocking Nodal. Therefore, Nodal signaling is required to define a population of chordin.1+ cells and to restrict the recruitment of brain precursors within the BCNE as early as at blastula stage. We discuss our findings in Xenopus in comparison to other vertebrate models, uncovering similitudes in early brain induction and delimitation through Nodal signaling.

Embryonic development of the fire-eye-tetra Moenkhausia oligolepis (Characiformes: Characidae).

This study describes the embryonic development of Moenkhausia oligolepis in laboratory conditions. After fertilization, the embryos were collected every 10 min up to 2 h, then every 20 min up to 4 h, and afterwards every 30 min until hatching. The fertilized eggs of M. oligolepis measured approximately 0.85 ± 0.5 mm and had an adhesive surface. Embryonic development lasted 14 h at 25ºC through the zygote, cleavage, blastula, gastrula, neurula, and segmentation phases. Hatching occurred in embryos around the 30-somites stage. The present results contribute only the second description of embryonic development to a species from the Moenkhausia genus, being also the first for this species. Such data are of paramount importance considering the current conflicting state of this genus phylogenetic classification and may help taxonomic studies. Understanding the biology of a species that is easily managed in laboratory conditions and has an ornamental appeal may assist studies in its reproduction to both supply the aquarium market and help the species conservation in nature. Moreover, these data enable the use of M. oligolepis as a model species in biotechnological applications, such as the germ cell transplantation approach.

Embryonic and early larval development of two marine angelfish, Centropyge bicolor and Centropyge bispinosa.

Marine angelfish (family: Pomacanthidae) are among the most sought-after fish species in the saltwater aquarium trade. However, there is a lack of information in the literature on their early ontogeny. The objective of this study was to describe the embryonic and early larval development of two dwarf angelfish, the bicolour angelfish, Centropyge bicolor and the coral beauty angelfish, Centropyge bispinosa. The eggs of these two species were obtained from spontaneous spawning of the broodstock fish in captivity and incubated at 26.0 ± 0.2°C throughout the study. Fertilized eggs (n = 15) of both species are transparent, pelagic and spherical; the mean diameters of the eggs were measured at 703.6 ± 7.8 µm for C. bicolor and 627.6 ± 7.8 µm for C. bispinosa. The eggs of both species possessed a narrow perivitelline space, smooth and thin chorion, a homogenous and non-segmented yolk as well as a single oil globule. Overall, the observed embryonic development pattern of C. bicolor and C. bispinosa was very similar, and the main difference was the embryonic pigmentation pattern, which only became evident close to hatching. Larvae of both species started hatching at 13 h 30 min after fertilization, and the larval characteristics of both species also showed high levels of similarities. However, the mouth opening time for C. bicolor was 72 h after hatching (AH) and 96 AH for C. bispinosa. In general, the observed early ontogeny of C. bicolor and C. bispinosa also resembled that of other Centropyge species documented in the literature.

Embryonic development of the bullseye puffer Sphoeroides annulatus (Tetraodontidae): A morphofunctional approach to ontogenetic steps.

The embryonic development of the bullseye puffer, Sphoeroides annulatus, was characterized on the basis of the theory of saltatory ontogeny. This theory predicts a correlative relationship between the ontogeny-type in an altricial-precocial spectrum and the habitat that a species occupies within an unstable-stable environmental spectrum. Because S. annulatus inhabits a variety of unstable environments along a wide latitudinal range, the hypothesis that this species presents one of the most altricial embryonic developments among tetraodontids was tested. Based on major developmental events that marked the ontogenetic thresholds nine embryonic steps were identified. Developmental features such as small adhesives eggs, lack of vitelline circulation, small free embryos swimming up at hatching guided by positive phototaxis, and small first-feeding larvae actively swam in the water column, suggest that S. annulatus belongs to the reproductive guild of the nonguarders-lithopelagophils. Moreover, a comparative analysis of the developmental sequences, egg size, and first-feeding larvae size between tetraodontids confirms the hypothesis of this study and supports the evolutionary principle of the altricial-precocial spectrum postulated in the theory of saltatory ontogeny.

Generation of mouse-zebrafish hematopoietic tissue chimeric embryos for hematopoiesis and host-pathogen interaction studies.

Xenografts of the hematopoietic system are extremely useful as disease models and for translational research. Zebrafish xenografts have been widely used to monitor blood cancer cell dissemination and homing due to the optical clarity of embryos and larvae, which allow unrestricted in vivo visualization of migratory events. Here, we have developed a xenotransplantation technique that transiently generates hundreds of hematopoietic tissue chimeric embryos by transplanting murine bone marrow cells into zebrafish blastulae. In contrast to previous methods, this procedure allows mammalian cell integration into the fish developmental hematopoietic program, which results in chimeric animals containing distinct phenotypes of murine blood cells in both circulation and the hematopoietic niche. Murine cells in chimeric animals express antigens related to (i) hematopoietic stem and progenitor cells, (ii) active cell proliferation and (iii) myeloid cell lineages. We verified the utility of this method by monitoring zebrafish chimeras during development using in vivo non-invasive imaging to show novel murine cell behaviors, such as homing to primitive and definitive hematopoietic tissues, dynamic hematopoietic cell and hematopoietic niche interactions, and response to bacterial infection. Overall, transplantation into the zebrafish blastula provides a useful method that simplifies the generation of numerous chimeric animals and expands the range of murine cell behaviors that can be studied in zebrafish chimeras. In addition, integration of murine cells into the host hematopoietic system during development suggests highly conserved molecular mechanisms of hematopoiesis between zebrafish and mammals.This article has an associated First Person interview with the first author of the paper.

Embryonic development of teleost Brycon orbignyanus.

Brycon orbignyanus is an important large teleost that is currently on the list of endangered species, therefore studies on its reproductive biology and embryology are fundamental to help species conservation and recovery. The objective of this research was to characterize the events that occur during extrusion, fertilization and embryonic development of the species. The samples were collected at predetermined times, fixed and processed for light microscopy and scanning electron microscopy. The greenish oocytes were spherical, had translucent chorion and a mean diameter of 1.3±0.11 mm. The eggs had well defined animal and vegetative poles approximately 18 min post-fertilization. Stages from 2 to 128 blastomeres occurred between 20 min and 3 h post-fertilization (hPF), when the morula was characterized. The blastula stage was observed between 2 and 3 hPF, and the gastrula between 3 and 7 hPF, when the embryonic shield emerged and the cellular migration with the consequent formation of epiblast and hypoblast. At 8 hPF, the formation of the neural tube, above the notochord and the encephalic region, was observed, delimiting the forebrain, mesencephalon and rhombencephalon regions. From 11 hPF onward, the optic vesicle was formed close to the forebrain and the embryo tail was well developed. The optic vesicle was observed from 12 hPF onward, and the tail showed an intense movement that culminated with the rupture of the chorion and consequent hatching of the larva at 13 hPF and 27°C.

Differential sensitivity of developmental stages of the South American toad to a fungicide based on fludioxonil and metalaxyl-M.

Agricultural fungicide application in Argentina has increased twice since 2008, with Maxim® XL (2.5% fludioxonil +1% metalaxyl-M) as one of the most used fungicide formulation. The toxicity of this pesticide on Rhinella arenarum was assessed by means of continuous (from embryo and larval development) and 24-h pulse exposure standardized bioassays. Lethality was concentration- and exposure time-dependent. Maxim® XL caused a progressive lethal effect along the bioassays with higher toxicity on embryos than larvae, obtaining 50% lethal concentrations at 96, 336, and 504 h of 10.85, 2.89, and 1.71 mg/L for embryos, and 43.94, 11.79, and 5.76 mg/L for larvae respectively. Lethal 504-h no observed effect concentration values for embryos and larvae were 1 and 2.5 mg/L respectively. A stage-dependent toxicity of Maxim® XL was also demonstrated within the embryo development, with early stages more sensitive than the later ones, and blastula as the most sensitive developmental stage. The risk quotients obtained for chronic risk assessment determined a potential threat for the survival and continuity of R. arenarum populations under these conditions. The results indicate that the levels of the fungicide reaching amphibian habitats could be risky for the early development of this amphibian species. This study also emphasizes the necessity to evaluate the chronic effects of fungicides in pesticide risk assessment.

Synchronizing developmental stages in Neotropical catfishes for application in germ cell transplantation.

SummaryThe aim of this study was to describe the effect of temperature on the fertilization, early developmental stages, and survival rate of two Neotropical catfishes Pimelodus maculatus and Pseudopimelodus mangurus. After fertilization, the eggs were incubated at 22°C, 26°C, and 30°C, which resulted in fertilization rates of 96.95 ± 1.79%, 98.74 ± 0.76%, and 98.44 ± 0.19% for P. maculatus and 96.10 ± 1.58%, 98.00 ± 0.63%, and 94.60 ± 2.09% for P. mangurus, respectively. For P. maculatus, hatching occurred after 22 h 30 min post-fertilization at 22°C, 16 h 30 min at 26°C, and 11 h 20 min at 30°C, and the hatching rates were 43.87 ± 7,46%, 57.57 ± 17.49%, and 53.63 ± 16.27%, respectively. For P. mangurus, hatching occurred after 28 h 30 min post-fertilization at 22°C and 17 h 30 min at 26°C with respective hatching rates of 45.4 ± 21.02% and 68.1 ± 12.67%. For this species, all embryos incubated at 30°C died before hatching. Additionally, for P. maculatus, the larvae from the lower (22°C) and higher temperatures (30°C) presented increased abnormality rates, as observed in the head, tail and yolk regions. The lowest abnormality rate was detected at 26°C, which was considered the optimal incubation temperature for both species. The developed protocol enables the manipulation of embryonic development, which is important for the application of reproductive biotechniques, including chimerism and chromosome-set manipulation. The data obtained here are also important for the surrogate propagation of this species as P. mangurus was recently categorized as an endangered fish species.

Extra-embryonic tissue spreading directs early embryo morphogenesis in killifish.

The spreading of mesenchymal-like cell layers is critical for embryo morphogenesis and tissue repair, yet we know little of this process in vivo. Here we take advantage of unique developmental features of the non-conventional annual killifish embryo to study the principles underlying tissue spreading in a simple cellular environment, devoid of patterning signals and major morphogenetic cell movements. Using in vivo experimentation and physical modelling we reveal that the extra-embryonic epithelial enveloping cell layer, thought mainly to provide protection to the embryo, directs cell migration and the spreading of embryonic tissue during early development. This function relies on the ability of embryonic cells to couple their autonomous random motility to non-autonomous signals arising from the expansion of the extra-embryonic epithelium, mediated by cell membrane adhesion and tension. Thus, we present a mechanism of extra-embryonic control of embryo morphogenesis that couples the mechanical properties of adjacent tissues in the early killifish embryo.

Comparison of in vitro fertilization outcomes in ICSI cycles after human sperm preparation by density gradient centrifugation and direct micro swim-up without centrifugation.

OBJECTIVE: The aim of this study was to evaluate the efficacy of a non-expensive, easy and fast technique (direct micro swim-up) for sperm preparation in intracytoplasmic sperm injection (ICSI) treatments without the use of centrifuge. METHODS: We carried out a multicentric study in which a total of 140 ICSI-cycles were included. Sibling oocytes were divided into two groups according to semen preparation procedures: group A, discontinuous gradients (DG) (oocytes n=668), and group B, direct micro swim-up (MSU) (oocytes n=660). We analyzed differences in some key performance indicators. RESULTS: Fertilization rates were not statistically different between the DG and MSU groups (76.0% vs. 81.8%, respectively, p=0.248); while significant differences were found in blastulation rates per fertilized oocytes (41.7% vs. 58.5%, p=0.009), blastulation rates per D3 embryos (46.1% vs. 63.7%, p=0.045), and pregnancy rates (25.8% vs. 41.9%, p=0.045). The abortion rate was reduced in the MSU group as compared to DG, but not in a significant manner (12.9% vs. 29.4%, p=0.161). CONCLUSION: The MSU procedure has the advantage of reducing costs, time and mismatches, while ensuring comparable, and in some cases, better results than DG treatments. This technique can therefore be used as an alternative method to other conventional semen treatments.

Embryonic development in Zungaro jahu.

The aim of this study was to characterize the embryonic development of Zungaro jahu, a fresh water teleostei commonly known as 'jaú'. Samples were collected at pre-determined times from oocyte release to larval hatching and analysed under light microscopy, transmission electron microscopy and scanning electron microscopy. At the first collection times, the oocytes and eggs were spherical and yellowish, with an evident micropyle. Embryo development took place at 29.4 ± 1.5°C and was divided into seven stages: zygote, cleavage, morula, blastula, gastrula, organogenesis, and hatching. The differentiation of the animal and vegetative poles occured during the zygote stage, at 10 min post-fertilization (mpf), leading to the development of the egg cell at 15 mpf. From 20 to 75 mpf, successive cleavages resulted in the formation of 2, 4, 8, 16, 32 and 64 blastomeres. The morula stage was observed between 90 and 105 mpf, and the blastula and gastrula stage at 120 and 180 mpf; respectively. The end of the gastrula stage was characterized by the presence of the yolk plug at 360 mpf. Organogenesis followed, with differentiation of the cephalic and caudal regions, elongation of the embryo by the cephalo-caudal axis, and somitogenesis. Hatching occurred at 780 mpf, with mean larval total length of 3.79 ± 0.11 mm.

Morphology of gametes, post-fertilization events and the effect of temperature on the embryonic development of Astyanax altiparanae (Teleostei, Characidae).

The aim of this study was to describe the morphology of gametes, post-fertilization events and subsequent temperature effects on the early developmental stages of the neotropical species Astyanax altiparanae. The sperm of this species presents a typical morphology of teleost sperm with a spherical head (diameter = 1.88 µm), midpiece (diameter = 0.75 µm) and a single flagellum (length = 18.67 µm). The extrusion of the second polar body and fusion of male and female pronucleus were reported for the first time in this species. Additionally, we observed the formation of the fertilization cone, which prevents polyspermic fertilization. Developmental stages at 22°C, 26°C and 30°C gave rise to fertilization rates at 91.12, 91.42 and 93.04% respectively. Hatching occurred at 25 hpf at 22°C, 16 hpf at 26°C and 11 hpf at 30°C and the hatching rates were 61.78%, 62.90% and 59.45%, respectively. At 22°C, the second polar body was extruded at ≈6 mpf and the male and female pronucleus fused at ≈10 mpf. This fundamental information is important for the field and opens up new possibilities in fish biotechnology, including micromanipulation and chromosome-set manipulation.

Effect of temperature on embryonic development of Melanotaenia boesemani (Allen and Cross, 1982).

The present study aimed to provide data on the time required for Melanotaenia boesemani to complete embryonic development, and to investigate the influence that incubation at different temperatures caused in this species. The effects of temperature on the time and hatching rate are presented, as well as information related to embryonic development stages. After fertilization, the eggs were kept in incubators at 23, 26, 29 or 32°C and observed at predetermined times until the moment of hatching. Stages of development were identified and classified according to morphological and physiological characteristics. Oil droplets were visualized inside the eggs as well as filament adhesion present at the chorion. Embryonic development was similar to that observed in other species of the genus Melanotaenia with hatching and faster development in higher temperatures.

Initial development of Prochilodus hartii (Pisces: Prochilodontidae) submitted to induced reproduction.

The Prochilodontidae prepare for reproduction in captivity, but neither ovulation nor spawning occurs, thus requiring induced reproduction for breeding and restocking. This study analyzed for the first time the embryogenesis and larval ontogeny of P. hartii submitted to induced reproduction by hypophysation with crude common carp pituitary extract. The extrusion of oocytes and sperm was performed manually and fertilization was done using the dry method. After fertilization, the eggs were kept in incubators at 23°C. A stereomicroscope was used to measure egg diameter and to monitor embryo development. Samples of larvae were collected daily for 7 days for histological and biometric analyses. The recently extruded oocytes, non-hydrated, are spherical, grey, and non-adhesive with a diameter of 1480 ± 39 µm and after hydration, have a diameter of 2860 ± 120 µm. The positive response to hypophysation was 100% for females and 80% for males. Spawning occurred 7 h after the third hormonal dosage. The fertilization rate was 77% at 23°C. Blastopore closure occurred at 6 h 45 min and embryonic development was completed 36 h 10 min after fertilization. After 204 h post fertilization (hpf) the larvae reached a standard length of 6.56 ± 0.14 mm with the yolk sac completely resorbed. In P. hartii, the oral cavity opening occurred 132 hpf. The results of this study provide knowledge to better understand induced reproduction, breeding, and management of P. hartii, a species with a high potential for pisciculture, and which is commercially important in the Jequitinhonha River basin.

Involvement of the mitfa gene in the development of pigment cell in Japanese ornamental (Koi) carp (Cyprinus carpio L.).

A colored phenotype is an important feature of ornamental fish. In mammals, microphthalmia-associated transcription factor (MITF) was found to regulate the development of melanocytes. In this study, the mitfa cDNA was first cloned from the Japanese ornamental (Koi) carp (Cyprinus carpio L.), an important ornamental freshwater fish. The full-length cDNA of the mitfa gene contains 1634 bp, coding for 412 amino acids in Koi. The identity degree of mitfa amino acid sequences between the Koi carp and zebrafish is 92.9%. We tested the expression of the mitfa gene in several varieties of Koi using reverse transcription-polymerase chain reaction and found that the mitfa gene is highly expressed in the skin tissues of the Taisho sanke and the Procypris merus. Interestingly, the mitfa gene was also expressed in the Kohaku and Yamabaki ogon, although melanocytes were not observed in the skin. Koi carp embryos were transparent and colorless, while after hatching, different types of pigment cells successively emerged in a fixed order. In Taisho sanke, melanocytes first appeared in the trunk at approximately 12 days of age. Subsequently, there was a large area of melanocytes by 30 days of age. The expression level of the mitfa mRNA was low in early embryos and newly hatched larvae, and increased to high levels in 30-day-old fry. The results show that the mitfa gene is involved in regulating fish body color in the development of both melanocytes and pigment cells.

PIAS-like protein Zimp7 is required for the restriction of the zebrafish organizer and mesoderm development.

The Zmiz2 (Zimp7) protein and its homolog Zmiz1 (Zimp10) were initially identified in humans as androgen receptor co-activators. Sequence analysis revealed the presence of an SP-RING/Miz domain, which is highly conserved in members of the PIAS family and confers SUMO-conjugating activity. Zimp7 has been shown to interact with components of the Wnt/ß-Catenin signaling pathway and with Brg1 and BAF57, components of the ATP-dependent mammalian SWI/SNF-like BAF chromatin-remodeling complexes. In this work, we analyze the role of zygotic Zimp7 in zebrafish development. We describe evidence indicating that Zimp7 is required for mesoderm development and dorsoventral patterning. Morpholino-mediated reduction of zygotic Zimp7 produced axial mesodermal defects that were preceded by up-regulation of organizer genes such as bozozok, goosecoid and floating head at the onset of gastrulation and by down-regulation of the ventral markers vox, vent and eve1 indicating loss of the ventrolateral mesoderm. Consistently, embryos overexpressing zimp7 RNA exhibited midline defects such as loss of forebrain and cyclopia accompanied by transcriptional changes directly opposite of those found in the morphants. In addition, the patterning of ventralized embryos produced by the overexpression of vox and vent was restored by a reduction of Zimp7 activity. Altogether, our findings indicate that Zimp7 is involved in transcriptional regulation of factors that are essential for patterning in the dorsoventral axis.

Depression help-seeking attitudes and behaviors among an Internet-based sample of Spanish-speaking perinatal women / Actitudes y comportamientos de búsqueda de ayuda para la depresión en una muestra basada en internet de mujeres de habla hispana en período perinatal

OBJECTIVE: To examine attitudes and beliefs related to help-seeking for depression among an international sample of pregnant women, a majority of whom were Spanish-speakers residing in Latin America. METHODS: More than 6 000 (n = 6 672) pregnant women met eligibility criteria and consented to participate between 15 January 2009-12 August 2011. Of these, 1 760 with a Latino/Hispanic background completed a baseline survey as part of a larger study. Group comparisons analyzed attitudes and behaviors related to seeking help for depression, while a logistic regression was conducted to identify demographic characteristics related to help-seeking support. RESULTS: Of the participants, three-fourths reported experiencing depression during or after their current or past pregnancies. The majority of participants did not seek help, and generally reported ambivalence about their depressive symptoms and uncertainty as to the helpfulness of others. However, 44.8% did seek help, mostly by speaking to family or partners and reported feeling fear, shame, and embarrassment about their symptoms. A current major depressive episode and an income less than or equal to US$ 10 000 were significant predictors of help-seeking behaviors. CONCLUSIONS: Data from this study suggest that when feeling sad or depressed, perinatal Latinas tend to seek emotional support first from family and friends and may underutilize mental health services when needed. The Internet is an effective means for reaching perinatal women, especially those in areas of the world where there may be barriers to accessing psychological resources.

OBJETIVO: Analizar las actitudes y las creencias relacionadas con la búsqueda de ayuda para la depresión en una muestra internacional de mujeres embarazadas, la mayor parte de ellas hispanohablantes y residentes en América Latina. MÉTODOS: Más de 6 000 mujeres embarazadas (n = 6 672) cumplieron los criterios de selección y aceptaron participar entre el 15 de enero del 2009 y el 12 de agosto del 2011. De estas, 1 760 de origen latino o hispano completaron una encuesta básica que formaba parte de un estudio más amplio. Mediante comparaciones de grupo, se analizaron las actitudes y los comportamientos relacionados con la búsqueda de ayuda para la depresión, mientras que, mediante regresión logística, se determinaron las características demográficas relacionadas con la búsqueda de ayuda o apoyo. RESULTADOS: De todas las participantes, tres cuartas partes notificaron sentimientos de depresión durante o después de los embarazos actuales o pasados. La mayor parte de ellas no buscaron ayuda, y en general manifestaron ambivalencia acerca de sus síntomas depresivos e incertidumbre en cuanto a la capacidad de ayuda de otras personas. Sin embargo, 44,8% buscaron ayuda, principalmente hablando con familiares o compañeros, y notificaron sentimientos de temor, culpabilidad y vergüenza acerca de sus síntomas. Un episodio depresivo mayor actual y unos ingresos iguales o inferiores a US$ 10 000 fueron factores predictivos significativos de comportamientos de búsqueda de ayuda. CONCLUSIONES: Los datos de este estudio indican que, cuando se sienten tristes o deprimidas, las mujeres latinas en período perinatal tienden a buscar en primer lugar el apoyo emocional de la familia y los amigos, y podrían subutilizar los servicios de salud mental cuando son necesarios. La internet es un medio eficaz para llegar a las mujeres en período perinatal, especialmente a las que viven en zonas del mundo donde pueden existir barreras para el acceso a los recursos psicológicos.

Structural analysis of embryogenesis of Leiarius marmoratus (Siluriformes: Pimelodidae).

Embryological studies in fish species are useful to the understanding of their biology and systematics. The available biological data in Leiarius marmoratus are scarce and additional information about its reproductive biology is needed, mainly because this species has been commercially exploited and used in production of hybrid lineages. In order to evaluate the temporal-morphological embryonic modifications in L. marmoratus, samples of nearly 200 embryos were collected at random at different stages of development, starting from fecundation (time zero). Embryos were fixed in modified Karnovsk's solution and 2.5% glutaraldehyde, processed and analysed under optic and electron microscopy. The incubation period of L. marmoratus was equal to 14.42 h at a mean temperature of 28.3 ± 0.07°C. The following stages of embryonic development were established: zygote, cleavage, gastrula, organogenesis and hatching. These stages were divided into phases, as follows: cleavage - phases of 2, 4, 8, 16, 32 and 64 cells and morula; gastrula - phases of 25, 50, 75 and 90% of epiboly and blastopore closure; and organogenesis - neurula, segmentation and pre-larval phases. The embryogenesis of L. marmoratus was typical of neotropical teleosteans, with peculiarities in species development.

Description of the ontogenic and larval period of discus fish (Symphysodon aequifasciatus).

The aim of this study was to describe the embryonic and larval development of discus fish (Symphysodon aequifasciatus), and to determine the time required, hours post fertilization (hpf), for the emergence of various structures. To describe embryonic and larval stages, observations were made at regular periods under an optical microscope and images were taken with a digital camera attached to a microscope. The average temperature reached in the experimental tank was 27.9°C. Important facts in embryonic and larval development are described, such as the closure of the blastopore, which occurred at 31.5 hpf; a period of eruption, which occurred at 58.5 hpf; and a mouth opening, which occurred at 90.5 hpf; and larvae that exhibited oriented swimming and eating exogenous food at 136.5 hpf.