Embryonic and larval development of Brycon amazonicus (SPIX & AGASSIZ, 1829) / Desenvolvimento embrionário e larval de Brycon amazonicus (SPIX & AGASSIZ, 1829)

Abstract The objective of this study was to describe the embryonic and larval development of Brycon amazonicus, featuring the main events up to 50 hours after fertilization (AF). The material was provided by the Aquaculture Training, Technology and Production Center, Presidente Figueiredo (AM). The characterization was based on stereomicroscopic examination of the morphology of eggs, embryos and larvae and comparison with the literature. Matrinxã eggs are free, transparent, and spherical, with a perivitelline space of 0.56 ± 0.3 mm. The successive divisions give rise to cells with 64 blastomeres during the first hour AF. The gastrula stage, beginning 02 h 40 min AF, was characterized by progressive regression cells and the formation of the embryonic axis, leading to differentiation of the head and tail 05 h 30 min AF. From 06 to 09 h AF the somites, notochord, otic and optic vesicles and otoliths were observed, in addition to heart rate and the release of the tail. The larvae hatched at 10 h 30 min AF (29.9 °C), with a total length of 3.56 ± 0.46 mm. Between 19 and 30 h AF, we observed 1) pigmentation and gut formation, 2) branchial arches, 3) pectoral fins, 4) a mouth opening and 5) teeth. Cannibalism was initiated earlier (34 h AF) which was associated with rapid yolk absorption (more than 90% until 50 h AF), signaling the need for an exogenous nutritional source. The environmental conditions (especially temperature) influenced the time course of some events throughout the embryonic and larval development, suggesting the need for further studies on this subject.

Resumo O objetivo deste trabalho foi descrever o desenvolvimento embrionário e larval do Brycon amazonicus, caracterizando os principais eventos ocorridos até 50 h Após Fertilização (AF). O material é proveniente do Centro de Treinamento, Tecnologia e Produção em Aqüicultura em Presidente Figueiredo (AM). A caracterização foi feita com base na análise estereomicroscópica da morfologia dos ovos, embriões e larvas e comparação bibliográfica. Os ovos da matrinxã são livres, transparentes, esféricos com espaço perivitelínico de 0,56 ± 0,3 mm. As sucessivas clivagens originam células com 64 blastômeros na primeira hora AF. A gástrula, iniciada 02 h e 40 min AF caracterizou-se por progressiva involução celular e formação do eixo embrionário, culminando com diferenciação de cabeça e cauda com 05 h 30 min AF. De 06 às 09h AF foi observada a formação de somitos, notocorda, vesículas óptica, ótica e otólitos, além de batimentos cardíacos e liberação da cauda. As larvas eclodiram com 10 h 30 min AF (29,9 °C), com 3,56 ± 0,46 mm de comprimento total. Entre 19 e 30 h AF foram observadas: 1) pigmentação e formação do tubo digestivo 2) surgimento de arcos branquiais 3) nadadeira peitoral 4) abertura da boca e 5) surgimento dos dentes. O canibalismo iniciou mais precocemente (34 h AF), em relação aos trabalhos existentes com o gênero, o que associado à rápida absorção do vitelo (mais de 90% até 50 h AF), sinaliza a necessidade de ofertar recurso alimentar exógeno. As condições ambientais (especialmente temperatura e pH) influenciaram na abreviação de alguns eventos ao longo do desenvolvimento embrionário e larval, sugerindo a necessidade de estudos complementares a esse respeito.

Embryonic and larval development of Eugerres mexicanus (Perciformes: Gerreidae) in Tenosique: Tabasco, Mexico

Most studies on Eugerres mexicanus mainly consider biogeographic and systematic aspects and rarely address reproductive characteristics, which are useful for fishery population management plans. This study aimed at evaluating the ontogeny of E. mexicanus, based on 30 embryos and 30 larvae sampled by induced spawning of breeders, taken in February 2009 from the Usumacinta River in Tenosique, Tabasco, Mexico. All descriptions of the embryonic development were based on morphometric and meristic data and followed standard methods. Eggs, recovered at the gastrula stage, had an average diameter of 1.17mm (SD=0.08). The bud stage appeared during the first three hours of development, in which the posterior side was adhered to the vitellus; Kupffer´s vesicle was visible. Yolk-sac larvae hatched 18 hours after fertilization, exhibiting a light brown color and an average total length of 2.94mm (SD=0.70); the preflexion stage was reached eight days after hatching, with a total average length of 4.67mm (SD=0.50) and a total notochord length of 4.45mm (SD=0.50). The flexion stage was reached on the 16th day, with an average total length of 6.66mm (SD=1.53), while postflexion was reached on the 24th day, with 10.33mm (SD=1.45). The pre-juvenile stage was reached on the 33rd day, with a total length of 14.30mm (SD=0.93), showing IX spines and 10 rays and III spines and eight rays in the dorsal and anal fins, respectively. The juvenile stage was reached by the 45th day, with an average length of 28.16mm (SD=1.93) and average weight of 4.75g (SD=1.49). Prejuveniles showed an initial pigmentation with dark colored dots in the superior and inferior jaw and dispersed on the head, while juveniles presented the same pigmentation pattern, decreasing towards the margin of the caudal peduncle. In conclusion, the embryonic developmental stages of E. mexicanus were typical for the Gerreidae group. However, their morphometric characters were slightly different since the diameter and size of the drop of oil were bigger than those reported for marine species. In addition, regarding pigmentation, the yolk-sac larvae of E. mexicanus were olive and yellow on the margin of the notochord, which differs from those reported for other species. This is the first recorded report on the reproductive biology and early life development of this species.

La ontogenia se basó en 30 embriones y 30 larvas, obtenidos mediante la inducción del desove de reproductores provenientes de la ribera del río Usumacinta en Tenosique, Tabasco, México, recolectados en febrero de 2009. La descripción se fundamentó en el registro morfométrico y merístico. Los huevos fueron recuperados en estado de gástrula y presentaron un diámetro de promedio de 1.17mm (SD=0.08). Durante las primeras tres horas de desarrollo embrionario, se presentó la etapa de capullo, en la que se observó la región caudal adherida al vitelo, apreciándose la vesícula de Kupffer. Las larvas con saco eclosionaron a las 18 horas pos-fertilización, fueron de color marrón claro con un promedio de 2.94mm; (SD=0.70) de longitud total y alcanzaron la preflexión a los ocho días post-eclosión con una longitud total promedio de 4.67mm; (SD=0.50) y una longitud total del notocordio de 4.45; (SD=0.50). A los 16 días de la eclosión alcanzaron la flexión, con un promedio de 6.66mm; (SD=1.53) de longitud total. La postflexión se presentó a los 24 días con 10.33mm; (SD=1.45). Al llegar a los 33 días, se presentó la fase prejuvenil y llegaron a medir 14.30; (SD=0.93) de longitud total, presentando IX espinas y 10 radios en la aleta dorsal y III y ocho en la aleta anal. Los juveniles midieron 28.16; (SD=1.93) de longitud a los 45 días, con un peso promedio de 4.75g; (SD=1.49). Los prejuveniles presentaron una pigmentación inicial en la mandíbula superior e inferior con tintes oscuros en forma de puntos y de manera dispersa sobre la cabeza. En los juveniles se observó el mismo patrón de pigmentación, disminuyendo hacia el margen del pedúnculo caudal. Las características descriptivas de la etapa de desarrollo embrionario de E. mexicanus son típicas del período de desarrollo de los peces de la familia Gerreidae, en particular en el caso de las especies E. brasilianus y E. lineatus que habitan en ambientes marinos. Sin embargo, sus caracteres morfométricos son diferentes con respecto al diámetro y el tamaño de los huevos y de la gota de aceite, ya que en E. mexicanus son más grandes que los de las especies marinas y son similares a los de los peces de agua dulce. Con respecto a la pigmentación, la larva con saco de E. mexicanus presenta un olor olivo y amarillo sobre el margen del notocordio, lo cual difiere a lo reportado para E. lineatus,ya que en esta muestra un grupo de melanóforos entre los miomeros nueve al 13 como principal característica, y para Diapturus peruvianus por presentar tres manchas en el margen dorsal de los intestinos desde la inserción de la aleta pectoral hasta el ano. Los resultados de este estudio son los primeros registrados para esta especie y han generado información sobre aspectos de su biología reproductiva y el desarrollo de la vida temprana.

Embryonic development of Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida, Paludicola) / Desenvolvimento embrionário de Girardia tigrina (Girard, 1850) (Platyhelminthes, Tricladida, Paludicola)

The embryonic development of freshwater triclads is mainly known from studies of species of Dendrocoelum, Planaria, Polycelis, and, more recently, Schmidtea. The present study characterizes the development of Girardia tigrina (Girard, 1850) by means of optical microcopy using glycol methacrylate semi-thin sections. 94 cocoons were collected in the period from laying to hatching, with intervals of up to twenty-four hours. The sequence of morphological changes occurring in the embryo permitted the identification of nine embryonic stages. At the time of cocoon laying, numerous embryos were dispersed among many yolk cells, with a rigid capsule covering the entire cocoon. In the first stage (approx. up to 6 hours after cocoon laying), yolk cells and embryonic cells showed random distribution. Stage II (between 12 and 24 hours after cocoon laying) is characterized by aggregates of blastomeres, which later aggregate forming an enteroblastula. Approximately 2 days after cocoon laying (stage III), formation of the embryonic epidermis and embryonic digestive system took place, the latter degenerating during the subsequent stage. Stage V (until the fourth day) is characterized by the formation of the definitive epidermis. Between 4 and 6 days after laying, organogenesis of the definitive inner organs starts (stage VI). Approximately 14 days after laying (stage IX), formation of the nervous system is completed. At this stage, the embryo shows similar characteristics to those of newly hatched juveniles. The hatching of Girardia tigrina occurs in the period between twelve to twenty-two days after cocoon laying.

O desenvolvimento embrionário dos tricladidos é conhecido, fundamentalmente, por estudos realizados em espécies de Dendrocoelum, Planaria, Polycelis e, mais recentemente, Schmidtea. O presente estudo descreve o desenvolvimento embrionário de Girardia tigrina (Girard, 1850), a partir de análises realizadas em cortes histológicos seriados e semifinos de glicol-metacrilato, ao microscópio óptico. Noventa e quatro casulos foram coletados no período entre a postura e a eclosão, em intervalos de até vinte e quatro horas. A seqüência das modificações morfológicas no embrião permitiu a identificação de nove estágios embrionários. Na postura dos casulos, envoltos por uma cápsula rígida, observam-se numerosos embriões dispersos entre grande quantidade de células vitelinas. No estágio I (aproximadamente até 6 horas após a postura), as células vitelinas e as embrionárias mostram uma distribuição aleatória. O estágio II (entre 12 e 24 horas após a postura) caracteriza-se pela formação de agrupamentos de blastômeros, os quais posteriormente formam uma enteroblástula. Aproximadamente dois dias após a postura (estágio III), ocorre a formação da epiderme e do sistema digestivo embrionário, sendo que este último degenera no estágio seguinte. O estágio V (até o quarto dia após a postura) caracteriza-se pela formação da epiderme definitiva. Entre o quarto e o sexto dia posteriores à postura, começa a organogênese dos órgãos internos definitivos (estágio VI). Aproximadamente catorze dias após a postura (estágio IX), completa-se a formação do sistema nervoso. Neste estágio, o embrião já apresenta características similares aos espécimes juvenis. A eclosão de Girardia tigrina ocorre entre doze e vinte e dois dias após a postura dos casulos.

Desarrollo embrionario-larval del pez tropical Hemirhamphus brasiliensis (Beloniformes: Hemirhamphidae) a partir de huevos recolectados del medio natural

Embrionary-larval development of the tropical fish Hemirhamphus brasiliensis (Beloniformes: Hemirhamphidae) from eggs collected in the wild. The embryo formation and larval development of Hemirhamphus brasiliensis Linnaeus, 1758 (Pisces: Hemirhamphidae) is described from morula stage eggs collected on Sargassum sp. Thalii in the field (10°50’55.2" N y 64°09’467" W). The eggs were spherical, 1 923.54 ±72.35 µm diameter with several corionic filaments, and are striated. During the first 48 h the embryo developed cephalic vesicle, miomers, and a heart located on the external body surface, beating strongly and circulating colorless blood which became pigmented red later. Before hatching, the larva developed kidney, gut tract, liver and biliar vesicle, pectoral fins, four pairs of gill arches and the mouth. The larva hatched at 114 h, the body was torpedo-shaped, yellow-green, with several dendriform melanophores; the pelvic fin was observed 72 h post hatching. At 240 hours the metamorphoses was completed. When the larvae hatched they could ingest Artemia metanauplii. Rev. Biol. Trop. 56 (3): 1449-1458. Epub 2008 September 30.

Se describe la formación del embrión y el desarrollo larval del pez Hemirhamphus brasiliensis Linnaeus, 1758, a partir de huevos en estado de mórula, recolectados en el alga parda Sargassum sp. Los huevos eran esféricos con un diámetro de 1923.54 ±72.35 µm, con numerosos filamentos coriónicos y estrías en su superficie. Durante las primeras 48 h, el embrión desarrolló la vesícula cefálica, los miomeros y el corazón, el cual se ubicó en el exterior de cuerpo impulsando sangre incolora, la cual se pigmentó de rojo posteriormente. Antes de la eclosión se desarrollaron el riñón, estómago, hígado y la vesícula biliar, las aletas pectorales, cuatro pares de arcos branquiales y la boca. Las larvas eclosionaron a la 114 h, presentando el cuerpo robusto en forma de torpedo, verde-amarillo con melanoforos dendriformes. Al nacer ingirieron metanauplios de Artemia. A las 72 h después de la eclosión se observó el esbozo de la aleta pélvica y a las 240 h se completó la metamorfosis.

Expression of dorsal-ventral genes during early development of Rhynchosciara americana embryos

The establishment of dorsal-ventral polarity in Drosophila is a complex process which involves the action of maternal and zygotically expressed genes. Interspecific differences in the expression pattern of some of these genes have been described in other species. Here we present the expression of dorsal-ventral genes during early embryogenesis in the lower dipteran Rhynchosciara americana. The expression of four genes, the ventralizing genes snail (sna) and twist (twi) and the dorsalizing genes decapentaplegic (dpp) and zerknüllt (zen), was investigated by whole-mount in situ hybridization. Sense and antisense mRNA were transcribed in vitro using UTP-digoxigenin and hybridized at 55°C with dechorionated fixed embryos. Staining was obtained with anti-digoxigenin alkaline phosphatase-conjugated antibody revealed with NBT-BCIP solution. The results showed that, in general, the spatial-temporal expression of R. americana dorsal-ventral genes is similar to that observed in Drosophila, where twi and sna are restricted to the ventral region, while dpp and zen are expressed in the dorsal side. The differences encountered were subtle and probably represent a particular aspect of dorsal-ventral axis determination in R. americana. In this lower dipteran sna is expressed slightly later than twi and dpp expression is expanded over the lateral ectoderm during cellular blastoderm stage. These data suggest that the establishment of dorsal-ventral polarity in R. americana embryos follows a program similar to that observed in Drosophila melanogaster.

Desenvolvimento embrionário do Curimbatá Prochilodus lineatus (Valenciennes, 1836) (Cypriniformes, Prochilodontidae) / Embryonal development of the curimbatá Prochilodus lineatus (Valenciennes, 1836) (Cypriniformes, Prochilodontidae)

Através da análise da morfologia externa dos ovos e dos aspectos microscópicos de seus cortes histológicos, foram caracterizados 18 estádios durante o desenvolvimento embrionário do curimbatá Prochilodus lineatus, que ocorreu a uma temperatura média de 26 + 0,5 C e no período de 16 horas, desde a fertilizaçao até a eclosao das larvas.

A developmentally regulated lectin in Bufo arenarum embryos

We report the levels of an endogenous beta-galactoside lectin activity from Bufo arenarum whole embryos extracts and specific inhibition by saccharides at different developmental stages. Specific activity measured against trypsinized rabbit red blood cells showed relatively high and fluctualting levels during early stages (up to about 76 h post-fertilization) which fell to significantly lower and more constant values at late stages (77-264 h post-fertilization). Lactose is the most potent inhibitor of this lectin activithy, and saccharides having alpha-galactoside configurations are weaker inhibitors. At the last embryonic stage, the agglutinating activity showed a different sugar specificity which suggests either the modification of the preexistent lectin or the sybthesis of another type of lectin. The possible physiological roles of these in the blockage of polyspermy or in embryonic cell-cell interactions are discussed