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Laboratory experiments were carried out to evaluate juvenile and adult mortality in Musculium argentinum over a given period of time. Specimens of M. argentinum were collected in May 2009 from the evacuation channel of the Lautaro fish farm, Araucania Region, Chile (38°32′ S, 72°27′ W), and a laboratory experiment was carried out consisting of 2 treatments (T1 and T2), with 3 replications of each. In each treatment and replication, a plastic container (15×10×5 cm) was filled with water and dead leaf litter from the channel inhabited by the study species. During T1, the population density of the container was 100 individuals (D100); during T2, the population density was 60 individuals (D60). The individuals were allowed 2 days to adapt to their new environment. Every 7 days during the following 2 mo, the anteroposterior valve length of each specimen in each treatment was measured to an accuracy of 0.1 mm. Adults were measured using digital calipers, and juveniles were measured using a stereomicros...

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 (38°32′ S, 72°27′ W) and La Poza, Villarrica Lake (39°16′27″ S, 71°58′54″ W). Sixty specimens were collected monthly from each population. Valve length of each specimen of the sampl...

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.

The pill clams Pisidium chilense (d'Orbigny, 1846) and Pisidium huillichum (Ituarte, 1999) showed a 2C DNA content of 4.04 ± 0.4 pg and 2.35 ± 0.24 pg, respectively. The somatic DNA content of these 2 Chilean Pisidium Pfeiffer 1821 species is within the range described previously for diploid Heterodonta, despite the fact that both showed a high chromosome number (> 100–120 chromosomes) equivalent to the polyploid level described for other species of the genus. The nuclear DNA content is shown here for the first time for species of the family Sphaeriidae. The Pisidium, like other species, are not economically important as edible species, but they play a significant role in the dynamics of nutrient and energy cycles in freshwater bodies similar to that described for other Sphaeriidae species.

To evaluate the capacity for movement of freshwater mussels in sandy and sand-gravel substrates and to test their ability to differentiate among types and qualities of substrates, experiments were carried out in the laboratory and in the field, using Diplodon chilensis from Lake Panguipulli, Chile. The movement of mussels was greater in sandy than in sand-gravel substrates. In the absence of food, there was a significant preference for sandy substrate, and when mussels were offered sandy or sandgravel substrates with and without food they chose the substrate with food with no preference to substrate type. Under natural conditions mussel presence and abundance along time is regulated by variables with a synergistic effect, niche of which substratum is not always the major one.

Based on literature review and malacological collections, 168 native freshwater bivalve and five invasive species have been recorded for 52 hydrographic regions in South America. The higher species richness has been detected in the South Atlantic, Uruguay, Paraguay, and Amazon Brazilian hydrographic regions. Presence or absence data were analysed by Principal Coordinate for Phylogeny-Weighted. The lineage Veneroida was more representative in hydrographic regions that are poorer in species and located West of South America. The Mycetopodidae and Hyriidae lineages were predominant in regions that are richest in species toward the East of the continent. The distribution of invasive species Limnoperna fortunei is not related to species richness in different hydrographic regions there. The species richness and its distribution patterns are closely associated with the geological history of the continent. The hydrographic regions present distinct phylogenetic and species composition regardless of the level of richness. Therefore, not only should the richness be considered to be a criterion for prioritizing areas for conservation, but also the phylogenetic diversity of communities engaged in services and functional aspects relevant to ecosystem maintenance. A plan to the management of this fauna according to particular ecological characteristics and human uses of hydrographic regions is needed., Facultad de Ciencias Naturales y Museo

Se reporta el rango de distribucion actual de Musculium argentinum (D'Orbigny, 1835) y Musculium patagonicum Pilsbry 1911 en Chile sobre la base de colectas realizadas entre losanos 2002 al 2006. La caracterizacion morfologica y biometrica de las poblaciones estudiadas indican que M. argentinum se distribuye discontinuamente entre los paralelos 38°Sy41°Sy entre los meridianos 71 °0 y 72°0 habitando ambientes lacustres y fluviales. M. patagonicum fue registrado en un ambiente lacustre localizado en los 51°42'S; 72°25'0. Ambas especies son morfologicamente muy similares. M. argentinum difiere de M. patagonicum en que en el primero el contorno de sus valvas son marcadamente cuadrangulares o trapezoidales, con el extremo posterior suavemente truncado; con extremos superiores dorsales marcadamente cuadrangulares, charnela poco consistente, recta o levemente curvada, presentando una relacion longitud de charnela vs longitud valvar constante. M. patagonicum es mas globoso en su contextura general, el contorno de sus valvas es mas redondeado, menos trapezoidal y con margen posterior no abrupto y el bosquejo general de las valvas no presenta esquinas marcadas en la region dorsal, caracteristica tipica de M. argentinum. La charnela de M. patagonicum es curvada nunca derecha o quebrada como en M. argentinum. El material colectado se encuentra depositado en la Coleccion Zoologica de la Universidad Catolica de Temuco y en la Seccion de Malacologia del Museo Nacional de Historia Natural, Chile.

The aim of the present study was to experimentaly evaluate the capability of the freshwater mussel Diplodon chilensis as a potential depurator of residual waters in fish farming. With this purpose, the present study was carried out at the fish farm of the School of Aquaculture of the Catholic University- Temuco, Chile (38º46'S; 72º38'W). The experimental design consisted of 12 poly vinyl chloride trays of 50x20x20cm corresponding to 3 treatments with 3 replicates each treatment and their respective controls. Each tray contained sterilized sand substratum and running water from a trout feeding tank. The treatments 1, 2, 3 contained 15, 30 and 60 mussels respectively, while the control trays contained no mussels. The growth tank contained 5,2k/m³ of Oncorhynchus mykiss. The trouts were fed daily with 37g of fish food during the time of the experiment duration. At time 0 the wet weight and length of each mussel was measured to determine the physiological state of the specimens through the Condition index. At the onset of the experiment it was determined the mortality and the Condition index of each individual. Also water samples from each tray corresponding to the 3 treatments, their respective replicates and controls were taken at time 0, 30 and 60 days to determine: total suspended solids, total dissolved solids, dissolved oxygen, total phosphorous, ammonium, nitrite, nitrate, conductivity, temperature, pH and chemical oxygen demand (COD). In a parallel way the percentage of organic matter and COD in the substratum of each of the treatment trays and their respective controls were determined. D. chilensis showed more efficiency in diminishing the concentrations of total suspended solids, total phosphorous, nitrite and the chemical oxygen demand. Values of the mentioned parameters decreased in direct relation to mussel density and time elapsed. Water COD data showed a high system efficiency percentage, corroborated by the substrate organic matter and substrate CDO data. These results, valid for an experimental scale show that D. chilensis is efficient in water depurator used on fish farming activities, suitable for rural fish farming

El propósito del presente estudio fue comprobar si han ocurrido cambios, después de 16 años, en los patrones de abundancia, distribución espacial y estructura de talla de la almeja de agua dulce Diplodon chilensis en sustratos arenosos y areno-pedregosos del sector Chauquén del Lago Panguipulli. Los resultados indican que las almejas en 1987 y 2003 presentan una distribución espacial agregada en ambos sustratos y con una mayor fuerza de la agregación en los sustratos areno-pedregosos que arenosos. La densidad fue significativamente mayor en sustrato areno-pedregoso, tanto en 1987 (P < 0,001) como en el 2003 (0,001< P < 0,01). No se presentaron diferencias significativas (P > 0,05) en densidad entre los distintos años dentro de un mismo tipo de sustrato. La estructura de talla en ambos sustratos y periodos estudiados no varió mayormente, registrándose sin embargo en 2003 juveniles en ambos sustratos, lo que indicaría que ha ocurrido reclutamiento. Se discuten estos resultados en relación al rol que desempeñan estos bivalvos en el ecosistema y en su potencial uso en la evaluación ecológica de ambientes lacustres.

Se entregan antecedentes que establecen que Diplodon patagonicus (D'Orbigny 1835) señalado como especie presente en la región Neo tropica-Patagonia por Graf & Cummins (2007) corresponde aDiplodon chilensis patagonicus (D'Orbigny 1846) (sensu Haas 1969).

The extent of the northern distribution range of Diplodon chilensis is reported herein from specimens collected in the Rio Grande, an affluent of the Rio Limari located to the south of the village of Carachilla (30o28'S;71o05'W)

Se presenta el estado actual del conocimiento de los bivalvos dulceacuicolas chilenos. Las especies descritas a la fecha, pertenecen a las familias Hyriidae, representada solo por el genero Diplodon con dos especies (D. chilensis y D. solidulus) y Sphaeriidae con tres generos: Pisidium con siete especies (P. chilense, P. magellanicum, P. lebruni, P. observationis, P. meierbrooki, P. huillichum y P. llanquihuense), Sphaerium con dos especies (S. lauricochae y S. forbesi) y Musculium con dos especies (M. argentinum y M. patagonicum). Entidades subgenericas y subespecificas son reconocidas solo para Hyriidae. Se propone a Pisidium chilense, P. huillichum, P. llanquihuense, P. lebruni y D. solidulus como especies endemicas de Chile. Se senala la distribucion geografica de las especies, se analizan las implicancias que generan para la taxonomia, las variaciones fenotipicas experimentadas por los hiridos, las causas de la declinacion de las poblaciones y los vacios de conocimiento en ambas familias. Se reportan los especialistas en el tema y las colecciones existentes.

La poliploidia es un caracter inusual en moluscos bivalvos. Sin embargo, datos citogeneticos documentados para especies de la subfamilia Sphaeriinae (familia Sphaeriidae) del hemisferio norte muestran numeros cromosomicos que varian desde 36 hasta ca. 247. La almeja dulceacuicola Musculium argentinum (D'Orbigny 1835) presenta un numero cromosomico 2n = ca. 130, lo cual muestra que la poliploidia tambien estaria presente en esferidos sudamericanos. Estos antecedentes citogeneticos sugieren que Sphaeriinae podria constituir un complejo poliploide maduro

Entregamos las lecciones aprendidas de un proyecto de relocalizacion de largo plazo llevado a cabo con el hirido Diplodon chilensis. El documento analiza las causas de la declinacion de las poblaciones en Chile y el uso de la relocalizacion como una herramienta de conservacion y manejo de la biodiversidad acuatica. Las lecciones aprendidas analizan las consideraciones que deben cautelarse antes, durante y despues de llevado a cabo el proceso de relocalizacion y las implicancias ecologicas, sanitarias y evolutivas de los programas de relocalizacion. Concluimos que la relocalizacion es una herramienta adecuada para la conservacion y manejo de las poblaciones de almejas de agua dulce y que se puede llevar a cabo exitosamente tomando las consideraciones antes senaladas

RESUMEN 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 ABSTRACT 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

Con el propósito de conocer cualitativamente la alimentación y la conducta alimentaria de la almeja de agua dulce Diplodon chilensis, se analizó mediante estudios de laboratorio y de campo el comportamiento alimentario y el contenido digestivo de especímenes procedentes de sustratos areno-pedregosos y arenosos del Lago Panguipulli y se relacionó con la oferta ambiental existente en el sustrato (fitobentos) y en el agua (fito-plancton). El análisis del contenido digestivo de los especímenes y los resultados experimentales, indican que Diplodon chilensis tiene una alimentación mixta en base a fitoplancton, fitobentos y materia orgánica existente en el plancton y en el bentos To determine qualitatively, feeding and alimentary behavior of the freshwater mussel, Diplodon chilensis, it was studied by means of field and laboratory studies the alimentary behavior and the digestive content of specimens inhabiting sand-gravel and sandy substrates of Lake Panguipulli; the digestive content of D. chilensis specimens was correlated to the environmental food offer existing in the substrate (phytobenthos) and in the water (phytoplankton). The digestive content analysis of the specimens and the experimental results show that D. chilensis has a mixed feeding based on phytoplankton, phytobenthos and organic matter existent in the plankton and benthos

The karyotype of a freshwater population of Diplodon chilensis located in La Poza area of the Villarrica Lake (39º18'S; 72º05'W), Southern Chile, was studied. The chromosomes were obtained by squash of cleaving embryos, previously treated with colchicine and fixed in ethanol-acetic acid 3:1 at 4ºC and stained using the Feulgen reaction. Diplodon chilensis showed a diploid karyotype of 2n = 34, with metacentric and submetacentric chromosomes. This work is the first approach to cytogenetic characterization of Chilean populations of this species.