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Reproduction estrategies
No full textElasmobranchs are an evolutionarily conserved group that has success- fully survived for over 400 million years. The permanence of elasmobranch populations has largely depended on the reproductive strategies of the population, as the primary requirement for successful propagation of any species and their individuals is the ability to reproduce. In vertebrates, reproductive strategies are regulated by the brain-gonadal axis, which controls the synthesis of reproductive hormones triggering all aspects related to reproduction. This chapter details the different reproductive strategies employed by elasmobranchs, from the wider range of reproductive modes including oviparity (egg-laying) and different forms of viviparity (live- bearing); followed by a description of the different reproductive cycles, from seasonal to continuous, displayed by both sexes. Finally, the role of reproductive hormones in both females and males regulating gametogenesis and the different reproductive cycles are discussed. The endocrine control of the elasmobranch reproductive strategies are preserved throughout vertebrate evolution, however they are distinct within this group.Fil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
A review on the morphology of ovarian follicles in elasmobranchs: A case study in Rhizoprionodon taylori
Get PDFThe identification of the elasmobranch secondary ovarian follicles and their function can be challenging and the inconsistent use of terminology derived from other taxa is a matter of ongoing debate. In this study, the available information on the histology of the elasmobranch secondary ovarian follicles derived from atresia (preovulatory follicles) or ovulation (postovulatory follicles) is reviewed highlighting their morphology and steroidogenic capacity. Based on this literature review, the ovarian follicles of the Australian sharpnose shark Rhizoprionodon taylori were classified according to their preovulatory or postovulatory origin. Two types of secondary follicles originating from atresia of developing follicles (atretic previtellogenic follicles) and ripe follicles (atretic vitellogenic follicles), and one type of postovulatory follicle were identified throughout the reproductive year of this species. Morphological similarities of the elasmobranch secondary ovarian follicles and their variations in different species denote the difficulty to classify them. Given the multiple origins of ovarian follicles, their poorly understood functions and capacity to supply steroids, visual identification of these structures and the use of terminology derived from mammalian and other vertebrate studies (with the exception of the corpora lutea as a temporary endocrine gland) is not advisable. J. Morphol. 278:486–499, 2017.Fil: Waltrick, Daniela S.. James Cook University; Australia. Western Australian Fisheries and Marine Research Laboratories; AustraliaFil: Simpfendorfer, Colin A.. James Cook University; AustraliaFil: Awruch, Cynthia Andrea. James Cook University; Australia. University of Tasmania; Australia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentin
Variables reproductivas e inmunológicas de peces marinos
No full textLos datos refieren a variables inmunológicas y reproductivas obtenidas de muestras de sangre de peces marinos. Los datos fueron obtenidos en el marco del proyecto de investigación Estado de salud reproductiva e inmunológica en peces marinos expuestos a contaminación antrópica (PICT-2013-3006)Fil: Sueiro, Maria Cruz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Palacios, María Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Somoza, Gustavo Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentin
Unique aspects of reproductive energetics and endocrinology among Chondrichthyes
No full textChondrichthyan fishes (sharks, rays, skates, and chimaeras) boast an array of at least ten reproductive strategies ranging from oviparity (egg-laying) to viviparity (live-bearing). Although reproduction in this taxon has been a topic of interest since the early 1900s, ongoing research continues to uncover nuances in the way these fishes reproduce. Indeed, over time, the focus on classifying reproductive strategies has shifted toward an interest in female maternal energetic strategies rather than discrete categories. This article presents an updated array of reproductive strategies, focusing on a spectrum of maternal energetic inputs. It underscores that the classification of reproductive strategies is becoming increasingly complex as more species are studied. This article also highlights gaps in chondrichthyan reproductive endocrinology, noting that most basic research has been limited to three sex steroid hormones and a few model species. Further work is needed to deepen the understanding of reproductive endocrine mechanisms, which can then be applied to reproduction in wild populations for improved management and conservation. Finally, the article outlines new avenues to address the long-standing gaps in the reproductive literature of chondrichthyan fishes.Fil: Wheeler, Carolyn. James Cook University; AustraliaFil: Brooke, Anderson N.. Arizona State University; Estados UnidosFil: Beckah, Campbell. Arizona State University; Estados UnidosFil: Sulikowski, James A.. State University of Oregon; Estados UnidosFil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentin
Conserving the Next Generation: Perspectives in Elasmobranch Reproductive Research
No full textThe inherent vulnerability of elasmobranchs (i.e., sharks, skates, rays) to extinction stems from their conservative life history traits, particularly those related to reproduction. Traditional studies on elasmobranch reproductive biology relied on lethal sampling techniques, which do not align with current conservation objectives. This chapter provides an overview of current and emerging non-lethal methodologies for studying elasmobranch reproduction. These include hormone analyses, advanced imaging technologies, and the development of intrauterine satellite-linked transmitters. These non-lethal techniques can and should be combined with other research domains, such as movement ecology and climate change impacts, to provide a more comprehensive understanding of elasmobranch ecology—a subject that has remained elusive for many decades.Fil: Brooke, N. Anderson. Arizona State University; Estados UnidosFil: Awruch, Cynthia Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Beckah, Campbell. Arizona State University; Estados UnidosFil: Sulikowski, James A.. State University of Oregon; Estados UnidosFil: Wheeler, Carolyn. James Cook University; Australi
Chondrichthyan research in South America: Endocrinology overview and research trends over 50 years (1967–2016) compared to the rest of the world
No full textThe endocrine system plays a crucial role in regulating the activity of cells and organs among vertebrates, including the class Chondrichthyes. Accordingly, Chondrichthyan endocrinology publications have been steadily increasing in the global literature. However, while interest in South American Chondrichthyan research has been growing over the last 50 years, the field of endocrinology related to Chondrichthyans has been limited. Understanding the trajectory of a scientific discipline assists researchers and stakeholders in making decisions regarding which research areas require further attention. Further, visualisation techniques based on bibliometric analysis of scientific publications assist in understanding fluctuations in the trends of specific research fields over time. In this study, Chondrichthyan research publications over time were analysed by creating visualisation maps using VOSviewer bibliometric software. Trends in South America Chondrichthyan research with an emphasis on endocrinology were explored over a 50-year period (1967–2016). These trends were compared with Chondrichthyans research worldwide for the more recent 15-year period (2002–2016). The number of South America Chondrichthyan scientific publications increased from six during the 1967–1981 period to 112 in 2016. However, only eight papers were found published in the area of Chondrichthyan endocrinology research. Fisheries, reproduction and taxonomy were the dominate research areas in South America over the 50 years. For the more recent 15 years, South American publications comprised 11% of the total literature published globally. While South America research outputs fluctuated closely with global research trends, differences appeared when comparing areas of growth. This study describes the trends in Chondrichthyan research literature globally and more specifically in South America. Although South American countries may never contribute to the same scale as the wider international scientific community, the future of Chondrichthyans would strongly benefit from the contributions of the many diverse research groups around the world.Fil: Awruch, Cynthia Andrea. University of Tasmania; Australia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Somoza, Gustavo Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Baldock, Clive. University of Tasmania; Australi
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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