1,720,962 research outputs found
Morphological and chemical description of the stylets of the red octopus, Enteroctopus megalocyathus (Mollusca: Cephalopoda)
Full text linkThis paper provides the first morphological and chemical description of the stylets (vestigial shell) of Enteroctopus megalocyathus, a large, commercially and ecologically important benthic species that is fished along the southern coasts of Argentina and Chile. The stylets are thin, semi-transparent curved structures embedded in the muscular tissue of the dorso-lateral regions of the mantle, and placed inside an epithelial sac. Rostral and post-rostral parts and a bend could be distinguished. Differences in the curvature of the post-rostral parts allow the discrimination of left and right stylets. In recent years these structures have received attention because of their potential use as a tool for age determination, based on interior growth rings. The elemental composition inside stylets can also assist in reconstructing environmental histories, and in determining dispersal and population structure. The length of the different parts and the maximum diameter at the bend were measured and compared between sexes and between left and right stylets. Transverse cuts were used to describe histological structures, the nucleus and the white core that surrounds it, and growth increments. Constituent chemical elements were analysed with a scanning electron microscope equipped with an X-ray energy-scattering microanalyzer. No significant differences between sexes were detected in the relative length of the post-rostral and rostral parts of the stylets. These relative lengths could, however, be of taxonomic value at the generic level. Two types of concentric increments were observed; the embryonic nucleus of the stylets was amorphous and did not present growth increments. The distribution of chemical elements in the stylets is also described.Fil: Marquez, Federico. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin
Morphometry of the northern Patagonian sympatric populations of Loligo sanpaulensis and Loligo gahi
No full textLoligo gahi and Loligo sanpaulensis (Mollusca: Cephalopoda), two squid species presently under exploitation in the south-west Atlantic, are sympatric in coastal waters of northern Patagonia. In the present study, the morphometry of both species' northern Patagonian populations was analysed and compared. Relationships between the morphometric variables and mantle length, the standard measure of size for squids, are allometric in most cases. Weight and fin length show different rates of growth relative to mantle length in males and females of both species. Fin length, fin width and mantle length are the best morphometric variables to discriminate the mantle/fin complexes. Free rachis length, gladius length and gladius width are the most useful to separate both species' pens. The best discrimination of the tentacles is provided by the diameter of the central and marginal suckers and the number of teeth on the three largest sucker rings. Discriminant functions are provided to allow the classification of individuals from both species and the identification of pens and tentacle clubs found in predators digestive contents.Fil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
Reproductive cycle and population structure of Loligo sanpaulensis of the northeastern coast of Patagonia
Full text linkThe squid Loligo sanpaulensis is distributed from southern Brazil to northern Patagonia. Previous studies have been conducted on the reproduction of this species in northern and central areas of its distribution. In northern Patagonia, lower and more variable temperatures were expected to cause sharper patterns in the temperature-regulated aspects of the reproduction. Periodic sampling was conducted from December 1996 to July 1999, and main biological characters and maturity stages were registered. Average mantle length (ML) was 55.1 mm (n = 1455). Large specimens were most abundant in November–March and small specimens were found in April–July. Sex ratio was significantly different from 1:1 (10 females:7 males). Mean ML at maturity was 65.3 mm in males and 77.6 mm in females. Mature specimens and recruits were found in summer. During fall, the largest size classes disappeared and juveniles were abundant. Throughout winter, juveniles progressively disappeared, and recruits were present. In late spring mature specimens entered the sampling area. A single spawning season from late spring to summer was observed. The disappearance of the largest size classes occurred three to four months latter than that reported for Mar del Plata (38°S).Fil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
The eggs and hatchlings of the octopus Robsonella fontaniana (Cephalopoda: Octopodidae)
Full text linkVery little is known about the life history of Robsonella fontaniana. In particular, there are no descriptions of the early life stages that enable correct identification of samples taken from the wild. In this work, eggs and hatchlings are described from egg clutches obtained in the field with brooding females and incubated until hatching. Individual eggs exhibited marked differences in stages of embryonic development within egg clutches or even within a single egg string. For one clutch collected at early stages of embryonic development, embryogenesis took 91 days at 11.5 °C and for a second clutch at intermediate developmental stages it took 68 days at 11 °C and 39 days at 14 °C. For the later clutch the hatching period lasts 25 days at 14 °C. The eggs and paralarvae were small, with an egg length of 3.9-5.2 mm, a dorsal mantle length of 2-3 mm and a total paralarvae length of 3.4-6.0 mm. Chromatophore shape and distribution presented a very distinctive pattern. Characteristics of the eggs, egg strings and paralarvae make it possible to distinguish the early stages of R. fontaniana from those of other octopodid species found off the Atlantic coast of Patagonia.Fil: Ortiz, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin
First report of pseudohermaphroditism in cephalopods
Full text linkSeveral malformations have been reported for cephalopods, involving a variety of internal and external structures. However, so far there are no published records of pseudohermaphroditism for the class. During a study of the reproductive biology of the red octopus, Enteroctopus megalocyathus (Gould 1852) in Golfo Nuevo, Patagonia, Argentina, we caught a specimen with a complete female reproductive system, with a normal terminal organ and an incomplete male spermatophoric complex. Histological comparisons with normal males and females did not reveal any testicular tissue in the ovary, so we suggest that this individual may represent the first case of pseudohermaphroditism in a cephalopods. When considering the potential causes of this abnormality, the influence of endocrine disruptors with an exogen origin should not be discarded. For instance, tributyltin contamination, as recorded previously in the gulf, and its relation to imposex in gasteropods should not be underestimated. Aditionally, this animal confirm that in immature octopus normal development of male ducts and glands is possible in the absence of testicular tissue.Fil: Ortiz, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentin
Ommastrephes bartramii (Le Sueur, 1821) and Todarodes filippovae Adam, 1975 (Cephalopoda, Ommastrephidae): Coastal records in Argentina
Full text linkOmmastrephes bartramii and Todarodes filippovae are ommastrephid squids characterized as ‘truly oceanic’ and ‘nerito-oceanic’ species respectively. O. bartramii has a cosmopolitan, discontinuous distribution in subtropical and temperate waters, from surface to 1500 m depth (Dunning, 1998a; Nesis, 1987; Roper et al., 1984). In the South Atlantic it occurs at 14°–27°S in the East (Roeleveld, 1989) and at 27°–45/48°S in the West (Brunetti et al., 1999). Recent reviews on its systematics, distribution and biology (Dunning, 1998a) and its fisheries biology and potential in the southern hemisphere (Dunning, 1998b) and in the Argentine Sea (Brunetti et al., 1999) have been presented. T. filippovae extends from surface to 1200 m depth (Nigmatullin, 1989). It shows a circumpolar distribution in the Southern Ocean, being present in the Antarctic Convergence Zone (Roper et al., 1984 ), in sub-Antarctic waters (mainly 35°–50ºS, up to 17°S in the Peru Current), in Antarctic intermediate waters (up to 33°S in the southeastern Atlantic) (Roeleveld, 1989), in the Subtropical and Subantarctic Fronts (Dunning and Wormuth, 1998; Xavier et al., 1999), and only occasionally in the Argentine Sea (Brunetti et al., 1999). A recent overview on its systematics and biology is given by Dunning and Wormuth (1998). This paper reports the studies on the first specimens of O. bartramii and T. filippovae found alive in Argentine coastal waters.Fil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Baron, Pedro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Kuba, Luisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Un panorama sobre los cefalópodos en la franja costera Argentina
No full textEn el Mar Argentino y la región oceánica adyacente se han listado más de 50 especies de cefalópodos. Se reconocen especies de distribución oceánica, nerítica y especies típicamente costeras. En este trabajo se revisan los conocimientos y las líneas de investigación recientes sobre los principales cefalópodos hallados en la franja costera de Argentina, entre los cuales se destacan los estudios realizados en los pulpos Octopus tehuelchus d ́Orbigny, 1834 y Enteroctopus megalocyathus (Gould,1852), y en los calamares Illex argentinus (Castellanos 1960) y Doryteuthis sanpaulensis (Brakoniecki, 1984) referidos a la estructura y dinámica poblacional, ecología trófica, embriología, reproducción, morfología, rol ecológico en la estructuración de las comunidades y estudios pesqueros y acuícolas.Fil: Ortiz, Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina. Universidad Tecnológica Nacional. Facultad Regional Chubut; ArgentinaFil: Crespi Abril, Augusto Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Storero, Lorena Pia. Universidad Nacional del Comahue. Instituto de Biología Marina y Pesquera Almirante Storni; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Re, Maria Edith. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; ArgentinaSegundo Congreso Argentino de MalacologíaMendozaArgentinaAsociación Argentina de Malacologí
Variations on the Author
Full text link“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
- …
