Elena Juana Galíndez

The ovary of the bignose fanskate Sympterygia acuta Garman, 1877 (Chondrichthyes, Rajidae) in the Bahía Blanca estuary, Argentina: morphology and reproductive features.

Chondrichthyes have become an important economic resource in recent years. In spite of this importance, there is little knowledge about their reproductive biology, especially of species from the south-western Atlantic. In this work, we study the morphology and histology of the ovary of Sympterygia acuta. The results show that oogonia were present only in the immature females (stage I of maturity scale), whereas specimens in stages II and III of maturity displayed oocytes in all developmental steps. The most important histological features that vary throughout oocyte development are the presence or absence of yolk, the number of types and layers of follicular cells and the degree of development of the thecae. Follicular cells are, at least, of two different types. Finally, a new point of view for the determination of maturity stages in the field based on the size of follicles is discussed.

Spleen of Dasypus hybridus (Mammalia, dasypodidae): a light and electron microscopic study.

Armadillos are relictual mammals important as models for biomedical studies. They contain adaptative and primitive characteristics in both anatomical and physiological aspects. In this study we describe the splenic histology and cytology of the “mulita,” Dasypus hybridus. Organ samples were processed for light and electron microscopy study. The microanatomy of the organ samples as well as their different cell types are described. The spleen is non‐sinusoidal, with the typical arrangement for storage functions. White pulp is lightly diffuse. Red pulp is a meshwork of circulating, immunocompetent and hemopoietic cells. Differences with other studied members of the group are discussed. The general structure of the organ agrees with the semi‐fossorial habit of the species. Persistence of myeloid activity in the adult suggests the existence of specific inductive functions of the stroma. Better knowledge of this fact may give further insight on the phylogeny of hemopoiesis. Anat Rec 258:286–291, 2000.

The spleen of Zaedyus pichiy, (Mammalia, Dasypodidae): a light and electron microscopic study.

Armadillos are ancient mammals important as models for biomedical, evolutive and ecological studies, because they have adaptive and primitive morpho‐physiological characteristics. In this work we study the splenic microarchitecture of the ‘Patagonian Piche’, Zaedyus pichiy, as an attempt to understand the relationship between the organizational plan of the organ and the particular features of this species.

Ovarian Folliculogenesis in the Smallnose Fanskate Sympterygia bonapartii (Müller & Henle, 1841) (Chondrichthyes, Rajidae)

Los Condrictios se han convertido en un recurso economico importante en las ultimas decadas, siendo Argentina uno de los paises que mas explota tiburones y rayas, incluso a niveles que exceden los limites de varias especies. A pesar de esto, es poco lo que se conoce sobre la biologia reproductiva de este grupo, particularmente en especies del Hemisferio Sur. En este trabajo se estudian los estadios mas relevantes de la foliculogenesis en Sympterygia bonapartii. Los resultados muestran que las ovogonias estan presentes tanto en ejemplares inmaduros como subadultos. Las caracteristicas mas importantes que varian a lo largo del desarrollo folicular son el numero de capas y tipos celulares que constituyen el epitelio folicular, el desarrollo de proyecciones de las celulas de la granulosa y el grado de desarrollo de las tecas. Las celulas foliculares son, al menos, de dos tipos y ambos emiten proyecciones que atraviesan la zona pelucida. La teca externa presenta caracteristicas compatibles con la actividad sintetica. Foliculos atresicos de distintos tamanos estan presentes en ejemplares de todos los estadios de madurez sexual. Estos resultados se discuten en un marco fisiologico y adaptativo.

The Female Reproductive System of Zearaja chilensis (Guichenot, 1848) (Chondrichthyes, Rajidae): Gametogenesis and Microscopic Validation of Maturity Criteria

Fil: Wehitt, Anahi. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Bahia Blanca. Instituto de Ciencias Biologicas y Biomedicas del Sur. Universidad Nacional del Sur. Departamento de Biologia, Bioquimica y Farmacia. Instituto de Ciencias Biologicas y Biomedicas del Sur; Argentina

Morphological indicators of initial reproductive commitment in Mustelus schmitti (Springer 1939) (Chondrichthyes, Triakidae): folliculogenesis and ovarian structure over the life cycle

This work provides information about the sexual commitment and the folliculogenesis of the gatuzo, Mustelus schmitti. A total of 112 females of all maturity stages were fished in the Bahía Blanca estuary, between 2009 and 2010. The oogonia were present throughout the life cycle of the animals. The folliculogenesis follows a pattern similar to other elasmobranchs. The granulosa layer keeps monolayered throughout the folliculogenesis, but with two cell types in the vitellogenic follicle. The zona pellucida forms in the primordial follicles. The thecal system shows a connective inner layer and a glandular outer sheath. The microscopic beginning of the sexual commitment, indicated by the vitello hoarding, takes place in follicles from 500 micrometres, while the macroscopic evidence appears in follicles of 2500-3000 micrometres. The results presented in this study suggest that the fishery pressure may affect a susceptible range of sizes of the species, not previously considered and provides a biological framework for the development of fisheries policy.

The spleen of Mustelus schmitti (Chondrichthyes, Triakidae): A light and electron microscopic study

The spleen ofMustelus schmitti is described, being an elongated organ running dorsally along the stomach and surrounded by a thin capsule without muscular tissue. The classical division between red and white pulps was evident, with a marginal sinus surrounding the latter. Numerous ellipsoids were located in the red pulp, inside nodular-like structures, or in the marginal sinus. Two types of reticular cells were apparent as well as macrophages and melanomacrophages. Hemopoiesis was present through immature and mature cells of the erythroid and thrombocytoid lineages, but no evidence of granulopoiesis was found. Comparison amongMustelus species and between chondrichthyan and mammalian spleens are made.

Ultrastructure and morphometry of ovarian follicles in the armadillo Chaetophractus villosus (Mammalia, Dasypodidae)

Ultrastructural and morphometric changes in oocyte and surrounding granulosa cells during armadillo follicular growth are described. Primordial, intermediary, early and late primary, secondary, tertiary and preovulatory Graafian follicles were found. From primordial to Graafian follicle, granulosa cells increase in height, become multilayered while fluid-filled spaces arise among them in the tertiary follicle stage. As the follicle expands the oocyte is located eccentrically and grows in size. From primordial to secondary stage organelles develop in number and complexity and many vesicles start arising in the cytoplasm at the secondary stage. From tertiary follicle stage the number of mitochondria decreases. In follicular cells, secreting-related organelles expand, but mitochondrial number decreases according to the follicle expansion. Intercellular junctions between both cell types increase. The morphometrical study shows a biphasic pattern of oocyte and follicle growth. The morphological baseline here provided will be essential for further comprehension of the reproductive biology in armadillos.

Morphology and dynamics of male gametogenesis in Sympterygia bonapartii (Chondrichthyes, Rajidae) from Northern Patagonia

The smallnose fanskate, Sympterygia bonapartii Muller & Henle, 1841 is one of the most disembarked items in commercial harbors in Argentina. In this work, the microscopic architecture of mature male gonads and the dynamics of cysts development are analyzed as a contribution to awareness of the reproductive biology of the species. Some biological data related to reproduction are given as well. Two seasons were sampled (fall and spring) and length classess frequency distribution and maturity stages frequency distribution are given. Size at first sexual maturation for males was estimated at 57 cm of total length. Testes are symmetric, peer, lobed, with several germinal zones. Inside the gonads, there are many spermatocysts, containing reproductive cells at the same developmental stage. On the basis of their cytological and microanatomical features, several maturative degrees of the spermatogenic series were differentiated. Few Leydig cells were recognized at the interstitial tissue among cysts. The microscopic and semiquantitative analysis performed in this work provides morphological information about male gametogenesis and some biological data for the North Patagonian population of this economically and ecologically important species.

Histological Remarks of the Uterus of Sympterygia acuta (Garman, 1877) and Sympterygia bonapartii (Müller & Henle, 1841) (Chondrichthyes; Rajidae)

Los condrictios constituyen un clado sumamente conservado y vulnerable a la explotacion, que ha cobrado una importancia creciente en los ultimos anos. Sin embargo, existe poca informacion sobre los aspectos morfologicos relacionados con la reproduccion; tanto asi, que la estructura del utero en hembras gravidas solo ha sido estudiada en profundidad en una especie ovipara. El presente trabajo describe las caracteristicas morfologicas, histologicas e histoquimicas del utero de dos especies de Rajidos del genero Sympterygia a lo largo del ciclo de vida. Ambas especies presentan uteros pares que desembocan independientemente en un seno urogenital comun. El utero de las hembras inmaduras es filiforme, translucido y poco especializado. Cuando se inicia el desarrollo sexual, todo el sistema genital exhibe un cambio direccional y progresivo. En todas las hembras estudiadas, independientemente del grado de madurez, se encontraron las mismas cuatro tunicas a lo largo del utero: una mucosa, compuesta por un epitelio de revestimiento y un corion, una submucosa, una muscular y una serosa. Los cambios mayores en la estructura del utero a lo largo del ciclo de vida ocurren a nivel de la mucosa. En el utero de hembras maduras, gravidas o no gravidas, se pueden reconocer tres regiones claramente diferenciables, craneal, media y caudal, que varian tanto en la estructura como en la afinidad histoquimica de la mucosa, asi como en el grosor de la tunica muscular. Los resultados del presente trabajo se discuten en un contexto fisiologico, filogenetico y adaptativo.