From egg to embryo in marsupial frogs.

Marsupial frogs (Hemiphractidae) evolved exceptional mechanisms for the conquest of terrestrial life. These adaptations include very large eggs. In some species eggs reach 10mm in diameter, and are considered to be the largest in frogs.

A display of Developmental Biology in Ibero-America.

This issue of the International Journal of Developmental Biology is dedicated to Ibero-America, and includes research articles from Argentina, Brazil, Chile, Colombia, Ecuador, Mexico, Panama, Puerto Rico, and Uruguay. It also describes the history of developmental biology in several Ibero-American countries. Moreover, the volume contains interviews with scientists living in the region and abroad.

Experiences with the marsupial frogs: reminiscences of a developmental biologist.

This article provides a brief account of the career of Eugenia M. del Pino. Casual events and serendipity played important roles in modeling her career as a developmental biologist.

Embryogenesis of Marsupial Frogs (Hemiphractidae), and the Changes that Accompany Terrestrial Development in Frogs.

The developmental adaptations of the marsupial frogs Gastrotheca riobambae and Flectonotus pygmaeus (Hemiphractidae) are described and compared with frogs belonging to seven additional families. Incubation of embryos by the mother in marsupial frogs is associated with changes in the anatomy and physiology of the female, modifications of oogenesis, and extraordinary changes in embryonic development. The comparison of early development reveals that gene expression is highly conserved.

The extraordinary biology and development of marsupial frogs (Hemiphractidae) in comparison with fish, mammals, birds, amphibians and other animals.

The study of oogenesis and early development of frogs belonging to the family Hemiphractidae provide important comparison to the aquatic development of other frogs, such as Xenopus laevis, because reproduction on land characterizes the Hemiphractidae. In this review, the multinucleated oogenesis of the marsupial frog Flectonotus pygmaeus (Hemiphractidae) is analyzed and interpreted. In addition, the adaptations associated with the incubation of embryos in the pouch of the female marsupial frog Gastrotheca riobambae (Hemiphractidae) and the embryonic development of this frog are summarized.

Analysis of Cell Size in the Gastrula of Ten Frog Species Reveals a Correlation of Egg with Cell Sizes, and a Conserved Pattern of Small Cells in the Marginal Zone.

We investigated the relationship between egg and cell sizes in the early gastrula of ten species of frogs with eggs of 1,100-3,500 μm diameters. We asked whether differences in cell size of the vegetal region, blastocoel roof, and marginal zone of the early gastrula were associated with egg size. Alternatively, we proposed that cell size differences may associate with gastrulation characteristics.

Transcription factors Mix1 and VegT, relocalization of vegt mRNA, and conserved endoderm and dorsal specification in frogs.

Protein expression of the transcription factor genes mix1 and vegt characterized the presumptive endoderm in embryos of the frogs Engystomops randi, Epipedobates machalilla, Gastrotheca riobambae, and Eleutherodactylus coqui, as in Xenopus laevis embryos. Protein VegT was detected in the animal hemisphere of the early blastula in all frogs, and only the animal pole was VegT-negative. This finding stimulated a vegt mRNA analysis in X.

Variation in the schedules of somite and neural development in frogs.

The timing of notochord, somite, and neural development was analyzed in the embryos of six different frog species, which have been divided into two groups, according to their developmental speed. Rapid developing species investigated were Xenopus laevis (Pipidae), Engystomops coloradorum, and Engystomops randi (Leiuperidae). The slow developers were Epipedobates machalilla and Epipedobates tricolor (Dendrobatidae) and Gastrotheca riobambae (Hemiphractidae).

Developmental diversity of amphibians.

The current model amphibian, Xenopus laevis, develops rapidly in water to a tadpole which metamorphoses into a frog. Many amphibians deviate from the X. laevis developmental pattern.

The gastrocoel roof plate in embryos of different frogs.

The morphology of the gastrocoel roof plate and the presence of cilia in this structure were examined in embryos of four species of frogs. Embryos of Ceratophrys stolzmanni (Ceratophryidae) and Engystomops randi (Leiuperidae) develop rapidly, provide comparison for the analysis of gastrocoel roof plate development in the slow-developing embryos of Epipedobates machalilla (Dendrobatidae) and Gastrotheca riobambae (Hemiphractidae). Embryos of the analyzed frogs develop from eggs of different sizes, and display different reproductive and developmental strategies.

Comparison of Lim1 expression in embryos of frogs with different modes of reproduction.

A polyclonal antibody was used to detect the expression of the homeodomain protein Lim1 (Lhx1) in embryos of Xenopus laevis, Engystomops randi, Colostethus machalilla and Gastrotheca riobambae. These frogs belong to four separate families, and have differences in their modes of reproduction and developmental rates. The expression of Lim1 in embryos of these frogs resembled the X.

The morphology of prehatching embryos of Caecilia orientalis (Amphibia: Gymnophiona: Caeciliidae).

The state of development of advanced embryos of the direct-developing Ecuadorian caecilian Caecilia orientalis (Caeciliidae: Gymnophiona: Amphibia) was examined. Because it is established that development is correlated with reproductive modes in a number of features, we included comparison with taxa that represent the major reproductive modes and all of the modern normal tables and ossification sequences. The embryos of C.

Embryogenesis and laboratory maintenance of the foam-nesting túngara frogs, genus Engystomops (= Physalaemus).

The vast majority of embryological research on amphibians focuses on just a single genus of frogs, Xenopus. To attain a more comprehensive understanding of amphibian development, experimentation on non-model frogs will be essential. Here, we report on the early development, rearing, and embryological analysis of túngara frogs (genus Engystomops, also called Physalaemus).

A comparative analysis of frog early development.

The current understanding of Xenopus laevis development provides a comparative background for the analysis of frog developmental modes. Our analysis of development in various frogs reveals that the mode of gastrulation is associated with developmental rate and is unrelated to egg size. In the gastrula of the rapidly developing embryos of the foam-nesting frogs Engystomops coloradorum and Engystomops randi, archenteron and notochord elongation overlapped with involution at the blastopore lip, as in X.

Comparative analysis of Xenopus VegT, the meso-endodermal determinant, identifies an unusual conserved sequence.

The transcription factor, VegT, is the meso-endodermal determinant in Xenopus laevis. We examined VegT orthologs from several anuran amphibians and the urodele amphibian, the Mexican axolotl. In addition to the conserved T-box, the DNA-binding domain, the orthologs share a conserved 57 amino acid domain at the C-terminal.

Gastrulation of Gastrotheca riobambae in comparison with other frogs.

Blastopore formation, the embryonic disk, archenteron and notochord elongation, and Brachyury expression in the marsupial frog Gastrotheca riobambae was compared with embryos of Xenopus laevis and of the dendrobatids Colostethus machalilla and Epipedobates anthonyi. In contrast with X. laevis embryos, the blastopore closes before elongation of the archenteron and notochord in the embryos of G.

Development of the dendrobatid frog Colostethus machalilla.

To provide a developmental correlate with other frogs, we prepared a normal table of development for the dendrobatid, Colostethus machalilla and analyzed the morphology of its early development. This frog reproduces in captivity and deposits moderately sized eggs (1.6 mm in diameter) in terrestrial nests.

Developmental biology in Ecuador: a 30-year teaching experience.

Developmental biology has been taught at the Pontificia Universidad Católica del Ecuador, in Quito for 30 years by the author. The experience of teaching development is described within the broader context of science in Latin America. It is recognized that developmental biology is poorly represented in research and teaching in this part of the world.

Bidder's organ in the toad Bufo marinus: effects of orchidectomy on the morphology and expression of lamina-associated polypeptide 2.

The Bidder's organ is an undeveloped ovary located anterior to the testis in male true toads (Bufonidae). The presence of sperm and oocytes, derived from the primordial germ cells of the male toad, provides an exceptional condition for the study of germ cell differentiation in vertebrates. In this study, the effects of orchidectomy on morphology and on lamina-associated polypeptide 2 (LAP2) expression were investigated in the Bidder's organ of Bufo marinus.

Expression of Brachyury during development of the dendrobatid frog Colostethus machalilla.

The expression of Brachyury (Bra) during development of Colostethus machalilla was analyzed with a polyclonal antibody. The observed molecular mass of Bra was of 48 kDa, as in Xenopus laevis. During cleavage, low levels of Bra were expressed.

Lamina-associated polypeptide 2 (LAP2) expression in fish and amphibians.

Somatic and germinal cells of 15 fish and 33 amphibian species were examined by SDS-PAGE followed by immunoblotting to determine the expression of LAP2 (lamina-associated polypeptide 2). LAP2 expression in frogs, salamanders and fish does not vary with the mode of reproduction. In fish and frog cells, a rim-like LAP2 positive region was detected around the nucleus by indirect immunofluorescence microscopy.

Urea is Necessary for the Culture of Embryos of the Marsupial Frog Gastrotheca riobambae, and is Tolerated by Embryos of the Aquatic Frog Xenopus laevis: (ureotelism/urea concentration in frog blood/culture of frog embryos/mesoderm induction).

Urea was found in the capsular fluid that bathes Gastrotheca riobambae embryos during incubation in the maternal pouch. The urea concentration in this fluid is higher than in blood from the mother, indicating that urea is accumulated by the embryo during the period of maternal incubation. Gastrotheca tadpoles tolerate up to 500 mM urea with 86% survival after 24 hours and die in solutions of 0.