Spermatogenesis and Histology of the Testes of the Caecilian, \u3cem\u3eChthonerpeton indistinctum\u3c/em\u3e

Macroscopically, the testes of Chthonerpeton indistinctum consist of a series of oval lobes. The number and size of lobes is variable in Chthonerpeton indistinctum. Histologically, the testes are divided into structural units, locules separated by septa of connective tissue. Inside of each locule spermatogenesis takes place in cysts of germinal cells that divide synchronically. Chthonerpeton indistinctum is divided chronologically into four stages of development based on the shape of the nuclei of the spermatids and their arrangement in the cyst: (1) round, (2) kidney shaped, (3) attenuate, and (4) bouquet arrangement

Histology of the Ovaries and Fat Bodies of \u3cem\u3eChthonerpeton indistinctum\u3c/em\u3e

Histological analysis revealed three different stages in the development of ovarian follicles of Chthonerpeton indistinctum. These stages are identified by (1) location of the oocyte in the ovary wall, (2) oocyte morphology and staining characteristics, (3) development of the zona pellucida, and (4) organization of the follicular layer. Atretic follicles and corpora lutea also were found. Fat bodies are composed of well-developed adipose tissue

A global community effort to decipher the unique biology of annual killifish

Over the past 50 years, annual killifishes arose as alternative model organisms for studies of vertebrate biology. The annual fish offers exceptional advantages for studies of genetics, genomics, developmental biology, population dynamics, ecology, biogeography, and evolution. They inhabit extremely variable freshwater environments in Africa and South America, have a short lifespan and a set of unique and fascinating developmental characteristics. Embryos survive within the dry substrate during the dry season, whereas the adult population dies. Thus, the survival of the populations is entirely dependent on the buried embryos that hatch the next rainy season. Although Old and New World species share similarities in their life cycle, they also have different adaptive responses associated with climate-related selective pressures. Therefore, contrasting different species from these areas is essential to understand unique adaptations to heterogeneous environment. A network of laboratories (United States, Czech Republic, Italy, Brazil, Chile, and Uruguay) is working and collaborating on many aspects of the biology of annual fishes. Participating researchers share projects and cross-training undergraduate and graduate students. These efforts resulted in two International Symposia (2010 and 2015) that took place in Montevideo and an international book. Herein, we summarize the progress made by this global community of scientists

The Neotropical Genus \u3cem\u3eAustrolebias\u3c/em\u3e: An Emerging Model of Annual Killifishes

Annual fishes are found in both Africa and South America occupying ephemeral ponds that dried seasonally. Neotropical annual fishes are members of the family Rivulidae that consist of both annual and non-annual fishes. Annual species are characterized by a prolonged embryonic development and a relatively short adult life. Males and females show striking sexual dimorphisms, complex courtship, and mating behaviors. The prolonged embryonic stage has several traits including embryos that are resistant to desiccation and undergo up to three reversible developmental arrests until hatching. These unique developmental adaptations are closely related to the annual fish life cycle and are the key to the survival of the species. Most of the available data on Neotropical annual fishes derive from studies on the genus Austrolebias. Herein, we review and summarize the available data on the evolution, reproduction strategy, developmental biology and conservation status of these Neotropical fishes

Gametogenesis en \u3cem\u3eChthonerpeton indistinctum\u3c/em\u3e (Gymnophiona: Typhlonectidae)

RESUMEN: Histológicamente, las gónadas de Chthonerpeton indistinctum son similares a las ya descritas para otras especies del orden Gymnophiona. Los lóbulos testiculares se hallan compartimentados en unidades estructurales denominadas lóculos. La espermatogénesis ocurre en cistos sincrónicos de células germinales. Durante la espermiogénesis se identifican cuatro estados consecutivos de desarrollo: 1) cistos de espermátidas redondeadas; 2) cistos de espermátidas arrifionadas; 3) cistos de espermátidas bastoniformes y 4) espermátidas en ramillete. El análisis histológico de los ovarios mostró la presencia de tres estados en la maduración de los folículos ováricos. Estas etapas pueden ser identificadas de acuerdo a: 1) ubicación del folículo en la pared ovárica; 2) morfología y características tintoreales del ovocito; 3) desarrollo de la membrana pelúcida; 4) organización de la capa de células foliculares. Fueron observados y descritos folículos atrésicos y cuerpos lúteos. SUMMARY Gametogenesis in Chthonerpeton indistinctum (Gymnophiona: Typhlonectidae) Histologically, the gonads of Chthonerpeton indistinctum are similar to others described for the orden Gymnophiona. The testes lobes are divided into structural units or locules. Spermatogenesis takes place in synchronic cysts of germinal cells. Four stages of development were identified during spermiogenesis: 1) cysts of round spermatids; 2) cysts of kidney-shaped spermatids; 3) cysts of attenuate spermatids, and 4) spermatids in a bouquet arrangement. The histological analysis of the ovaries showed the existence of three different stages of maturation of the ovarian follicles. These stages can be identified by: 1) location of the follicle in the ovary wall; 2) oocyte morphology and staining characteristics; 3) development of the zona pellucida, and 4) organization of the follicular layer. Atretic follicles and corpora lutea also were found

Estructura del ovario de \u3cem\u3eChthonerpeton indistinctum\u3c/em\u3e (Reinhardt y Lutken, 1862) (Amphibia: Gymnophiona) durante la gestación

La morfología e histología del ovario para varias especies del orden Gymnophiona ha sido reportada por Wake (1968, J. Morphol. 126, 291) y para C. indistinctum por los autores (1984, XXIV Reunión de Comunicaciones, Soc. Zool. Uruguay). Continuando con los estudios sobre el aparato genital de esta especie vivípara, se presenta ahora la estructura del ovario durante la gestación. Se procesaron con fines histológicos, ovarios de dos hembras grávidas colectadas en las costas de los Dep. Montevideo y San José en abril, 1983. El número de ejemplares trabajados es muy reducido dado lo difícil que resulta su colecta por los hábitos de la especie. Por esta razón el estudio encarado se refiere al estado del ovario en un período avanzado de la gestación, que era el que presentaban las hembras capturadas

Annual killifish adaptations to ephemeral environments: diapause I in two Austrolebias species

Background: Many organisms are able to survive in extreme environments by entering a state of dormancy. In dormancy, vital activities are reduced until environmental conditions are compatible with active life. Annual killifishes show a special developmental pattern characterized by a phase of dispersion-reaggregation of the blastomeres that separates epiboly from organogenesis, and the capability to enter dormancy in diapause. High tolerance to environmental stress confers annual killifish embryos the condition of extremophiles. At present, the questions of our research group are focused on the understanding of the mechanisms involved in diapause regulation through an interdisciplinary approach. As a first step, it is necessary to characterize diapauses at orphological and physiological levels and to evaluate induction cues under laboratory conditions. In this context, we characterized diapause I in two Austrolebias species. Results: Our experimental approach to induce apause I was successful and revealed the co-existence of two diapause I phenotypes named A and B instead of one. These phenotypes showed a tendency for lower total extractable RNA content compared with active developmental stages (80–100% epiboly and early reaggregate). Conclusions: These phenotypes are alternative diapause I stages and may have ecological relevance because both were found in embryos in natural ponds. Developmental Dynamics 246:848–857, 2017. VC 2017 Wiley Periodicals, Inc.CSIC: 147_C61034

Interacciones gaméticas en la corvina blanca, Miropogonias furnieri. Características celulares, ultraestructurales y funcionales de los gametos. Gametogénesis y fecundación

Orientador: Claudio Barro

Morfología y funciones del conducto de Müller de \u3cem\u3eChthonerpeton indistinctum\u3c/em\u3e (Reinhardt y Lutken, 1862) (Amphibia: Gymnophiona) en relación con los mecanismos reproductivos de la especie

El orden Gymnophiona comprende anfibios ápodos, ciegos, de hábitos cavícolas y acuáticos. Como consecuencia de estos hábitos resulta muy difícil su colecta, lo cual redunda en un escaso conocimiento de la biología del orden y sobre las relaciones filogenéticas del mismo. Una de las características más particulares del grupo se refiere a la modalidad reproductora, ya que aproximadamente el 50% de las especies presentan viviparidad y la totalidad de ellas tienen fecundación interna. Es por esta razón que el estudio del aparato reproductor ha sido encarado por diversos autores, en especial por Wake (1968, J. Morphol. 126: 291) con una perspectiva evolutiva. En la República Oriental del Uruguay el orden está representado por una única especie, Chthonerpeton indistinctum, perteneciente a la familia Typhlonectidae, especie vivípara. El presente trabajo forma parte de una serie de estudios sobre el aparato genital de C. indistinctum habiendo presentado anteriormente dos comunicaciones (de Sá, R. y N. Berois, 1984, XXIV Reunión de Comunicaciones, Sociedad Zoológica del Uruguay) sobre histología gonadal y gametogénesis. Proseguimos la labor iniciada presentando ahora la estructura del conducto de Müller en ambos sexos. Se procesaron para estudios histológicos conductos de Müller de ejemplares colectados en las costas de los departamentos de Montevideo y San José en abril y mayo de 1983, llegados allí como consecuencia de los desbordes de los ríos Paraná y Uruguay