Morphological types and seasonal variation in eggs of zooplankton species from bottom sediments in Bahia Blanca Estuary, Argentina

Resting egg production is a survival mechanism in zooplankton species against adverse environmental conditions. Egg accumulation in the upper layer of the bottom sediments is fundamental to the resurgence of the populations of these species when conditions become more favourable. Rotifers, such as Synchaeta sp. and planktonic copepods such as Acartia tonsa and Eurytemora americana are commonly found in Bahía Blanca Estuary and they produce resting eggs. We studied eggs isolated from samples of bottom sediments obtained from two sites located within the inner part of Bahía Blanca Estuary (Cuatreros Port and Ing. White Port). The aims of our work were to describe the morphological types of eggs found in bottom sediments; to try to identify to which species they belong; to corroborate the identity of some of them by means of incubations; and to determine either the spatial or seasonal presence of morphological types according to the sampling site. Sediment samples were collected from Cuatreros Port on a monthly basis from January to December 2003 and samples from Ing. White Port were collected from the area close to the industrial zone only in April 2004. All samples were treated following the sugar flotation method of Onbé. The eggs were observed under stereomicroscope and light microscope. Besides, incubation experiments with eggs were sometimes carried out. Five morphological types of eggs (type A, B, C, D and E) were found in the sediments from Cuatreros Port whereas three types of eggs were found at Ing. White Port (F, G and H). Of the 8 morphological types of eggs found in this study, only those of the rotifer Synchaeta sp. in Cuatreros Port and the copepod A. tonsa in the two sampling sites were confirmed to be respectively diapausal and “delayed -hatching”. As regards the seasonal variation of the eggs found in the sediments from Cuatreros Port and the active forms of the populations of Synchaeta sp. and A. tonsa, our study confirms the presence of eggs in the sediment either in periods of time during which no active forms have been previously reported in the plankton or in periods of time during which only some active forms have been reported at very low densities. Concerning the spatial variation at Ing.White Port, the differences in the presence of eggs across the sampling areas may be due to sediment modifications produced by anthropic impact, where industrial effluents are discharged.Fil: Diodato, Soledad Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Berasategui, Anabela Anhi. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Hoffmeyer, Monica Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina. Universidad Tecnológica Nacional; Argentin

Self-Quasi-Regularity in Certain Rings

Let R be an associative ring, not necessarily commutative and not necessarily having unity. Recall an element x in R is called quasi-regular if and only if solutions y and z exist for the equations x+ y - x*y = 0 and x + z - z*x = 0. In this case y=z, and the unique element y is called the quasi-inverse for x. It is well known that J(R), the Jacobson radical of R, is the unique largest ideal in R consisting entirely of quasi-regular elements. In this paper, we explore the implications of the case x is its own quasi-inverse. We call such elements self-quasi-regular. We determine some properties of sq(R), the set of all self-quasi-regular elements, for a general ring, and also compare this set to J(R). Then, we completely characterize the set sq(R) for all homomorphic images of Z, the integers, including the cardinality and membership of the set sq(Zn) for each choice of n

The evolutionary origin of postsynaptic signalling machineries – Insights from the single-celled sister group to the animals.

Choanoflagellates are a diverse monophyletic group of aquatic heterotrophic flagellates that form the sister group to the animals (Leadbeater, 2015). Genome surveys in two closely related choanoflagellate species – Salpingoeca rosetta and Monosiga brevicollis – showed that choanoflagellates and animals share many genes that are crucial for animal biology, including genes encoding proteins with functions at animal synapses (King et al., 2008; Alié and Manuel, 2010; Fairclough et al., 2013; Burkhardt et al., 2014). I surveyed 19 choanoflagellate transcriptomes (Richter et al., 2018) for the presence of putative homologs to a key set of synaptic proteins in order to extend our knowledge of the putative ancestral prerequisites for postsynaptic signalling machineries. Postsynaptic signalling machineries are crucial for signal reception and transduction as well as the regulation of signal transduction strength (Kennedy, 2000). Importantly, I could identify putative homologs to Shaker-like potassium channels, nitric oxide synthases and ionotropic glutamate receptors in several choanoflagellate species. The survey further showed that putative homologs of postsynaptic scaffolding proteins (Homer, Shank, and membrane associated guanylate kinases – MAGUKs including Dlg and MAGUK p55) occur in choanoflagellates that branch throughout the phylogenetic radiation of this group. The high degree of structural conservation in S. rosetta Dlg, and Homer homologs suggests that these proteins are of functional importance in choanoflagellates. Furthermore, my data indicate that the scaffolding function of both of these proteins is conserved in choanoflagellates. Combining ancestral protein reconstruction with in vitro binding assays, allowed me to establish that the capacity of Homer to bind its synaptic binding partner Shank presumably preceded the evolution of animals and choanoflagellates. Moreover, in an experiment using co-immunoprecipitation in combination with mass spectrometry analysis, I investigated in vivo S. rosetta Dlg interaction partners. I found evidence that the interaction between Dlg and MAGUK p55 might be conserved in choanoflagellates. This type of interaction was observed at animal postsynapses and tight junctions (Stucke et al., 2007; Rademacher et al., 2016). My data suggest that synaptic scaffolding complexes might have preceded the evolution of animals. Synaptic signalling machineries therefore presumably were built upon pre-existing structural scaffolds

Return Policy in Germany in the Context of EU Rules and Standards: Focussed Study by the German National Contact Point for the European Migration Network (EMN)

Die Studie beleuchtet Rückkehr aus Deutschland aus der rechtlichen Perspektive - von der Rückkehrentscheidung über die Möglichkeiten zur freiwilligen Rückkehr bis hin zur Abschiebung. Dabei steht im Vordergrund, wie das EU-Recht die jeweiligen Schritte beeinflusst. Rückkehr steht immer wieder im Zentrum der migrati­onspolitischen Debatte. In Folge der hohen Zuzugszahlen von Schutzsuchenden in den Jahren 2015 und 2016 ist auch die Zahl der abgelehnten Asylanträge gestiegen. Dadurch ist die Rückkehr von Personen ohne Aufenthaltsrecht zur politi­schen Priorität und zu einem kontrovers diskutierten Thema geworden.The study looks at return from Germany from a legal perspective – starting with the return decision, the study then presents the possibilities and conditions to return voluntarily as well as the enforcement of returns through a removal. Time and again, migration policy discussions have focused on return. As the number of asylum seekers jumped in 2015 and 2016, the number of rejected asylum applications rose as well – and as a result, returning those who are not entitled to stay in Germany to their countries of origin has become a political priority and a controversially discussed issue

Developments in Germany in the context of visa liberalisation: Study by the German National Contact Point for the European Migration Netwrk (EMN)

Das Working Paper 83 untersucht Entwicklungen in Deutschland im Zusammenhang mit der Visaliberalisierung für fünf Westbalkanstaaten sowie für Georgien, die Republik Moldau und die Ukraine im Zeitraum von 2007 bis 2017.Working Paper 83 examines developments in Germany in the context of visa liberalisation for five Western Balkans countries and for Georgia, Moldova and Ukraine between 2007 and 2017