Guía para el estudio de macroinvertebrados. I.- Métodos de colecta y técnicas de fijación.

El motivador de este trabajo ha sido generar estrategias de enseñanza tendientes a comprender a la diversidad biológica que nos rodea (haciendo hincapié en los macroinvertebrados), desde los distintos niveles de la enseñanza de las ciencias biológicas. Asimismo, sobre la base de nuestra experiencia en investigación en biología y en los distintos niveles de educación, podemos señalar que no son frecuentes de las actividades prácticas de campo y laboratorio en las clases de ciencia. Las mismas, constutyen recursos útiles para la enseñanza y aprendizaje de diferentes técnicas de muestreo específicas para cada grupo de organismos y para cada tipo de ecosistema: también para diseñar la forma de analizar los diferentes tipos de datos obtenidos e identificar las diferentes relaciones entre los grupos de macroinvertebrados con el ambiente en que viven. En esta contribución y a modo de una primera etapa, se plantea la forma de colecta y fijación (conservación) de macroinvertebrados, en relación con el ambiente en que se hallan. Los invertebrados, especialmente los artrópodos se pueden encontrar en cualquier época del año y en casi todos los ambientes. No es necesario ir muy lejos para encontrar la fauna buscada, de forma que con tan sólo un poco de capacidad de observación se pueden descubrir en los jardines, en los solares, en las quintas, en las hierbas de los caminos, en la playa, e incluso en el interior de nuestras viviendas. Por estas razones no debería presentar gran dificultad llevar a cabo un trabajo práctico de campo, incluso en los sitios que presentan marcados problemas de conservación. Los mismos deben realizarse teniendo en cuenta las directrices destinadas hacia la no depredación del ambiente y respetando la fauna de lugares protegidos (e.g. reservas y parques naturales), donde las capturas sin la debida autorización están prohibidas. El propósito de esta contribución es ofrecer la información indispensable para la captura y conservación de la fauna de invertebrados, y al mismo tiempo despertar la curiosidad del lector hacia estos grupos de animales. Sobre esta base, y teniendo en cuenta que hay que aclarar los por qué, para qué y el cómo diseñar estrategias y escenarios de intervención educativa para promover el aprendizaje, los objetivos de esta contribución son: 1) Proponer distintos métodos de captura adecuados para los diversos hábitats y formas de vida de los macroinvertebrados. 2) Describir diferentes técnicas de conservación del material colectado. Posteriormente, el objetivo de estudiar las relaciones existentes entre las distintas especies y con el ambiente donde viven, se realiza una contribución (Darrigran, et al., ms.), en la cual se describen los modelos básicos de muestreos necesarios para lograr esos objetivos. A partir de la adquisición de estos conocimientos, el docente estará en condiciones de elaborar recomendaciones didácticas tendientes a la sistematización y optimización del uso de estas herramientas como recurso didáctico para la enseñanza y aprendizaje de la biodiversidad que lo rodea. (Texto en Español. PDF tiene ochenta y seis paginas

Evaluation of sampling and analysis techniques for early detection of Limnoperna fortunei (Mytilidae) in limit areas of its distribution

The golden mussel Limnoperna fortunei (Dunker, 1857) (Mytilidae) is an invading species in continental waters in the Neotropical Region. L. fortunei is transported by human activities. Differing from fresh water bivalves native to the region, this mytilid has external fertility and a planktonic larval development similar to marine mytilids (Monteiros-Ribas et al.. 2006). The impact produced by L. fortunei on numerous South American rivers includes, among others, alteration of benthonic communities, alteration of fish diet, as well as severe macrofouling problems at industrial water intakes (Darrigran. 2002). Thus, it is fundamental to know the dynamic distribution of this invading species to explain its invading process and to have access to basic information to predict its distribution/ dispersion pattern.Facultad de Ciencias Naturales y Muse

Atomic time-of-arrival measurements with a laser of finite beam width

A natural approach to measure the time of arrival of an atom at a spatial region is to illuminate this region with a laser and detect the first fluorescence photons produced by the excitation of the atom and subsequent decay. We investigate the actual physical content of such a measurement in terms of atomic dynamical variables, taking into account the finite width of the laser beam. Different operation regimes are identified, in particular the ones in which the quantum current density may be obtained.Comment: 7 figure

Optimal atomic detection by control of detuning and spatial dependence of laser intensity

Atomic detection by fluorescence may fail because of reflection from the laser or transmission without excitation. The detection probability for a given velocity range may be improved by controlling the detuning and the spatial dependence of the laser intensity. A simple optimization method is discussed and exemplified

Quantum optical time-of-arrival model in three dimensions

We investigate the three-dimensional formulation of a recently proposed operational arrival-time model. It is shown that within typical conditions for optical transitions the results of the simple one-dimensional version are generally valid. Differences that may occur are consequences of Doppler and momentum-transfer effects. Ways to minimize these are discussed.Comment: 14 pages, 5 figure

Improvement by laser quenching of an "atom diode": a one-way barrier for ultra-cold atoms

Different laser devices working as ``atom diodes'' or ``one-way barriers'' for ultra-cold atoms have been proposed recently. They transmit ground state level atoms coming from one side, say from the left, but reflect them when they come from the other side. We combine a previous model, consisting of the stimulated Raman adiabatic passage (STIRAP) from the ground to an excited state and a state-selective mirror potential, with a localized quenching laser which produces spontaneous decay back to the ground state. This avoids backwards motion, provides more control of the decay process and therefore a more compact and useful device.Comment: 6 page

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay river and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Paraná Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.Facultad de Ciencias Naturales y Muse

Invasion process of Limnoperna fortunei (Bivalvia: Mytilidae): the case of Uruguay river and emissaries of the Esteros del Iberá Wetland, Argentina

Limnoperna fortunei (Dunker, 1857), during its invasion process in South America, has caused severe impacts both on natural environments altering native biodiversity, ecosystem structure and function-, and on man-made structures causing economic looses. Twenty-one samples were taken from the right bank of the Uruguay River, from tributaries of the Uruguay and Paraná Rivers, the drainage of the Esteros del Ibera Wetland. Based on this fieldwork, the presence of larvae and adults of L. fortunei was determined. Also, through the comparison of environmental characteristic with the known tolerance limits for the species, the possibility of its establishment in environments not yet invaded was determined. Most of the sampling stations have features that allow the development of stable populations L. fortunei, including the rivers that drain the Esteros del Ibera, allowing access of this invasive species to this important wetland.Facultad de Ciencias Naturales y Muse

Symbionts and diseases associated with invasive apple snails

This contribution summarizes knowledge of organisms associated with apple snails, mainly Pomacea spp., either in a facultative or obligate manner, paying special attention to diseases transmitted via these snails to humans. A wide spectrum of epibionts on the shell and operculum of snails are discussed. Among them algae, ciliates, rotifers, nematodes, flatworms, oligochaetes, dipterans, bryozoans and leeches are facultative, benefitting from the provision of substrate, transport, access to food and protection. Among obligate symbionts, five turbellarian species of the genus Temnocephala are known from the branchial cavity, with T. iheringi the most common and abundant. The leech Helobdella ampullariae also spends its entire life cycle inside the branchial cavity; two copepod species and one mite are found in different sites inside the snails. Details of the nature of the relationships of these specific obligate symbionts are poorly known. Also, extensive studies of an intracellular endosymbiosis are summarized. Apple snails are the first or second hosts of several digenean species, including some bird parasites. A number of human diseases are transmitted by apple snails, angiostrongyliasis being the most important because of the potential seriousness of the disease.Facultad de Ciencias Naturales y Muse