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‣ State of the art in taxonomy of Chilean freshwater bivalves: Advances and difficulties

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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An update of the Chilean freshwater bivalve taxonomy is presented. The bivalves described at present are adscribed to two families: Hyriidae represented only by the genus Diplodon with two species (D. chilensis and D. solidulus) and Sphaeriidae represented by three genera: Pisidium with seven species (P. chilense, P. magellanicum, P. lebruni, P. observationis, P. meierbrooki, P. huillichum and P. llanquihuense), Sphaerium with two species (S. lauricochae and S. forbesi), and Musculium with two species (M. argentinum and M. patagonicum). Sub-generic and sub-specific taxa are recognized for Hyriidae only. The present study includes the synonymy, type locality and geographic distribution where the species have been recorded. The most reliable diagnostic features for Hyriidae species identification are the hinge morphology in adult specimens, the presence or absence of the valve teeth, and their position and shape in larvae. At the generic level within Sphaeriidae, the most reliable taxonomic characters are the morphology and number of the siphons, and the size of both demibranchs. At the species level these characters are valve morphometry and morphology, which includes beak position, hinge features, shape and size of cardinal teeth, valve sculpture and pore density of the inner surface of valves. Results are discussed regarding advances and conflicts related to the taxonomic and systematic arrangement in both families...

‣ Estado de conocimiento de los bivalvos dulceacuicolas de Chile

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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The current knowledge about the Chilean freshwater bivalves is presented. The bivalves described at present are adscribed to two families: Hyriidae represented only by the genus Diplodon with two species (D. chilensis and D. solidulus) and Sphaeriidae represented by three genera: Pisidium with seven species (P. chilense, P. magellanicum, P. lebruni, P. observationis, P. meierbrooki, P. huillichum and P. llanquihuense), Sphaerium with two species (S. lauricochae and S. forbesi), and Musculium with two species (M. argentinum and M. patagonicum). Subgeneric and subspecific taxa are recognized for Hyriidae only. Pisidium chilense, P. huillichum, P. llanquihuense P. lebruni and D. solidulus are proposed as endemic species for Chile. It is allocated the geographic distribution of the species, the taxonomic implications of the phenotypic variations exhibited by hyrids, the causes of the declination of the populations and the lack of knowledge in both families are analyzed. Specialists on the field and the available collections are listed.; Se presenta el estado actual del conocimiento de los bivalvos dulceacuícolas chilenos. Las especies descritas a la fecha, pertenecen a las familias Hyriidae, representada sólo por el género Diplodon con dos especies (D. chilensis y D. solidulus) y Sphaeriidae con tres géneros: Pisidium con siete especies (P. chilense...

‣ Registro de poliploidia en la almeja dulceacuícola Musculium Argentinum (D'ORBIGNY 1835) (SPHAERIIDAE, VENEROIDA)

Fonte: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas. Publicador: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas.
Tipo: Artículo de Revista
Português
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La poliploidía es un carácter inusual en moluscos bivalvos. Sin embargo, datos citogenéticos documentados para especies de la subfamilia Sphaeriinae (familia Sphaeriidae) del hemisferio norte muestran números cromosómicos que varían desde 36 hasta ca. 247. La almeja dulceacuícola Musculium argentinum (D'Orbigny 1835) presenta un número cromosómico 2n = ca. 130, lo cual muestra que la poliploidía también estaría presente en esféridos sudamericanos. Estos antecedentes citogenéticos sugieren que Sphaeriinae podría constituir un complejo poliploide maduro.; The polyploidy is an unusual character in bivalve mollusks. However, cytogenetic data documented for north-hemispheric species of the subfamily Sphaeriinae (family Sphaeriidae), showed chromosome numbers ranging from 36 to ca. 247. The freshwater clam Musculium argentinum (D'Orbigny 1835) has a polyploid chromosome number 2n = ca. 130, which shows that polyploidy likewise may be present in South American sphaeriids. These cytogenetic data suggest that the subfamily Sphaeriinae could constitute a mature polyploid complex.

‣ Primer registro de Musculium Argentinum (D'ORBIGNY 1835) (BIVALVIA: SPHAERIIDAE) en aguas continentales chilenas

Fonte: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas. Publicador: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas.
Tipo: Artículo de Revista
Português
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Se comunica el primer registro de Musculium argentinum (d'Orbigny 1835) Bivalvia: Sphaeriidae) sobre la base de especímenes recolectados del fondo fangoso de piletas de engorda de la piscicultura de Lautaro (38° 32' S; 72° 27' W). La descripción y análisis morfométrico de los ejemplares coinciden con los entregados por Ituarte (1996). Con ello se extiende el rango de distribución longitudinal oeste de esta especie, aumentando la diversidad de esféridos para Chile.; The first record of Musculium argentinum (d'Orbigny 1835) (Bivalvia:Sphaeriidae) on the basis of specimens collected buried in the muddy bottom of raceways of Lautaro Fishfarming (38° 32' S; 72° 27' W ) is communicated. The description and morphometric analysis of the specimens are coincident with those described by Ituarte (1996) for this species. The finding adds a new species to Chilean continental malacofauna and extends the west longitudinal distribution range of this species, so increasing spheriid diversity in Chile.

‣ Gonadal organization and gametogenesis in musculium argentinum (Veneroida: Sphaeriidae) from a population in Southern Chile

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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The gonadal organization and cytological characteristics of gametogenesis in a population of the freshwater clam Musculium argentinum (d'Orbigny, 1835) are described. Sections of the rather small gonad demonstrate the existence of hermaphroditic specimens, and is composed of hermaphrodite follicles among the intestine coils in the posterior dorsal region of the body. Follicles contain male and female germ cells at different stages of maturation, which can be recognized by their shape, size, and nuclear features. Male germ cells are organized in cysts, and spermatocytes do carry out meiosis. Within follicles, male and female germ cells occupy different regions. Gonad activity throughout the year is coincident with the life cycle pattern of the M. argentinum population studied previously.

‣ Some aspects of the reproductive biology of two populations of Musculium argentinum (d'Orbigny, 1835) (bivalvia: sphaeriidae) from Southern Chile

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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Sphaerids have adopted a variety of life strategies that have allowed them to show a cosmopolitan distribution. Among these strategies, those related to reproduction, such as sexuality (hermaphroditism), offspring incubation, fertility, number of generations per year, times an individual reproduces during its lifespan, among others, have been decisive with regard to its permanence in time and space, and to colonize and maintain populations in permanent or temporary freshwater bodies. The aim of the current study is to compare reproductive traits of 2 Musculium argentinum populations inhabiting different environments (stream and lake) to determine the potential influence of the environment on reproduction of these populations. During 1 y (October 2006 to 2007) monthly samples were taken at 2 study sites: Lautaro stream (38032' S, 72[degrees]27' W) and La Poza, Villarrica Lake (39[degrees]16'27" S, 71[degrees]58'54" W). Sixty specimens were collected monthly from each population. Valve length of each specimen of the sample was registered to determine the size structure of each population. Fifty animals of known valve length were dissected to determine presence and number of brooding sacs in the inner hemibranches, number of embryos in each sac...

‣ Population dynamics and reproduction of a Musculium argentinum (Bivalvia: Sphaeriidae) population in Southern Chile, South America

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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The aim of the present study was to provide data about the population dynamics and reproductive traits of a Musculium argentinum (d'Orbigny, 1835) population inhabiting a channel next to the city of Lautaro in southern Chile. Results showed that M. argentinum size population structure varied during the study period, with brooding adults present throughout the year, with the highest frequencies in December 2002, and March, August and September 2003, producing offspring throughout the year. The smallest specimen brooding was 2.6 mm collected in May 2003 and the size of population first brooding corresponded to the 3.0-3.9 mm class size, collected in March 2003. M. argentinum at the study site is an ovoviviparous, iteroparous, sequential brooder, producing offspring throughout the year. These characteristics are attributed to the stable habitat.

‣ Present record of species of Musculium Link, 1807 (Bivalvia: Sphaeriidae) in Chile with notes on its morphology and biometry of its populations

Fonte: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas. Publicador: Universidad de Concepción, Facultad de Ciencias Naturales y Oceanográficas.
Tipo: Artículo de Revista
Português
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This study reports the present distribution range of Musculium argentinum (D'Orbigny, 1835) and Musculium patagonicum Pilsbry, 1911 in Chile, from sampling data carried out from 2002 to 2006. Morphological and biometric characteristies of the studied populations show that M. argentinum is discontinually distributed between 38°S-41°S and 71°W-72°W, inhabiting fluvial and lacustrine waters. M. patagonicum was reported in a lentic environment. (51°42'S; 72°25'W). Both species are morphologically very similar. M. argentinum differs from M. patagonicum because de first has their valves more markedly cuadrangular or trapezoidal with the posterior end slightly truncated, upper dorsal extremes markedly cuadrangular, hinge plate less solid, nearly straight or weakly curved. Constant hinge length-shell length ratio. The shell outline of M. patagonicum is not as markedly trapezoidal as in M. argentinum. In the first, the posterior margin is less abrutptly truncated, and the shell outline not sharp-cornered as is typical for M. argentinum. The hinge plate in M. patagonicum is always weakly curved never straight or broken as in M. argentinum. The collected material is deposited at the Zoological Collection of the Catholic University of Temuco and in the Malacological Section of the Nacional Museum of Natural History...

‣ Life histories and dynamics of stream and lacustrine populations of musculium argentinum (D'Orbigny, 1842) (Bivalvia: Sphaeriidae) from Southern Chile

Fonte: Universidade Católica de Temuco Publicador: Universidade Católica de Temuco
Tipo: Artículo de Revista
Português
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Life histories and population dynamics of two populations of Musculium argentinum, one inhabiting a fluvial environment and the other a lacustrine one, are compared. Musculium argentinum is oviparous, iteroparous, and sequential incubator, reproducing throughout the year. The life cycle pattern of the fluvial population, unlike the lacustrine one, is characterized by seasonal reproductive variations, more marked in spring and summer, higher fertility and population reproductive productivity (potential recruitment), higher number of marsupial sacs per hemibranch, and smaller size of first reproduction. The content of organic matter and water flow would be the main factors determining the higher population density observed in the fluvial population.