312 research outputs found
Medaka as a model for seasonal plasticity: Photoperiod-mediated changes in behaviour, cognition, and hormones
No full textTeleosts display the highest level of brain plasticity of all vertebrates. Yet we still know little about how sea-sonality affects fish behaviour and the underlying cognitive mechanisms since the common neurobehavioral fish models are native to tropical environments where seasonal variation is absent or reduced. The medaka, Oryzias latipes, which inhabits temperate zone habitats, represents a promising model in this context given its large phenotypic changes associated with seasonality and the possibility to induce seasonal plasticity by only manipulating photoperiod. Here, we report the first extended investigation of seasonal plasticity in medaka behaviour and cognition, as well as the potential underlying molecular mechanisms. We compared medaka exposed to summer photoperiod (16 h light:8 h dark) with medaka exposed to winter photoperiod (8 h light:16 h dark), and detected substantial differences. Medaka were more active and less social in summer photoperiod conditions, two effects that emerged in the second half of an open-field and a sociability test, respectively, and might be at least in part related to habituation to the testing apparatus. Moreover, the cognitive phenotype was significantly affected: in the early response to a social stimulus, brain functional lateralisation shifted between the two hemispheres under the two photoperiod conditions, and inhibitory and discrimination learning per-formance were reduced in summer conditions. Finally, the expression of genes encoding key pituitary hormones, tshss and gh, and of the tshss regulatory transcription factor tef in the brain was increased in summer photoperiod conditions. This work reveals remarkable behavioural and cognitive phenotypic plasticity in response to photoperiod in medaka, and suggests a potential regulatory role for the same hormones involved in seasonal plasticity of other vertebrates
Development of open-field behaviour in the Medaka, Oryzias latipes
No full textThe use of juvenile and larval fish models has been growing in importance for several fields. Accordingly, the evaluation of behavioural tests that can be applied to larvae and juveniles is becoming increasingly important. We tested medaka at four different ages (1, 10, 30, and 120 dph) in the open field test, one of the most commonly used behavioural assays, to investigate its suitability for larvae and juveniles of this species. We also explored ontogenetic variation in behaviour during this test. On average, adult 120-day-old medaka showed higher locomotor activity in terms of distance moved compared with younger fish. Our analysis suggests that this effect was derived from both quantitative changes in locomotion related to the ontogenetic increase in fish size as well as qualitative changes in two aspects of locomotor behaviour. Specifically, time spent moving was similar between 1-and 10-day-old medaka, but progressively increased with development. In addition, we revealed that adult medaka showed constant levels of activity, whereas younger medaka progressively reduced their activity over the course of the entire experiment. The thigmotaxis behaviour typically used to assess anxiety in the open field test emerged at 120 days post-hatching, even though a difference in the temporal pattern of spatial preference emerged earlier, between 10 and 30 days post-hatching. In conclusion, some measures of the open field test such as total distance moved allow behavioural phenotyping in the medaka of all ages, although with some degree of quantitative and qualitative developmental variation. In contrast, immature medaka appear not to exhibit thigmotactic behaviour
Palaeogroundwater of glacial origin in the Cambrian-Vendian aquifer of northern Estonia
No full textA strongly depleted stable isotope composition, absence of 3H and a low radiocarbon concentration are the main indicators of glacial origin of groundwater in the Cambrian-Vendian aquifer in northern Estonia. It is concluded from noble gas analyses that palaeorecharge occurred at temperatures c. 0°C. In some wells unexpectedly high gas concentrations have been found. Excess air, up to c. 50 %, is common but two-five times oversaturation is very unusual, requiring special processes and explanations, e.g. oversaturation may indicate recharge under highpressure conditions, perhaps by subglacial meltwater recharge through the aquifers. Analyses of the gas composition in some groundwater samples also showed a rather high concentration of CH4, indicating the influence of biogenic reactions in the subsurface that could cause the rather negative δ13C values. Results of δ13C analyses in two CH4 samples also show that the CH4 is most likely of a biogenic origin. Based on the isotope data, the results of noble gas analyses, and considering the palaeoclimatic and palaeoenvironmental situation in Estonia during the late Weichselian time, it is concluded that palaeorecharge of Cambrian-Vendian aquifer most probably occurred during the last glaciation, probably by subglacial drainage through the tunnel valleys
Carl Spitteler, Jonas Fränkel und Carl Albert Loosli - Freundschaft und Arbeitsgemeinschaft : zum aktuellen Stand der Affäre um Werk und Nachlass des Nobelpreisträgers Carl Spitteler
No full textCet article s'intéresse à la collaboration entre le poète Carl Spitteler, l'ancien détenu C. A. Loosli - surnommé le "Philosophe de Bümpliz" - et Jonas Fränkel, brillant spécialiste de la littérature originaire de Pologne. À travers leurs attitudes et leurs ambitions artistiques, ces individualistes et libres penseurs intellectuellement indépendants se sont opposés aux principales forces culturelles et politiques de la Suisse (allemande). Celles-ci ont toutefois réussi à écarter le professeur Fränkel, chargé par Spitteler de l'édition de ses oeuvres, et à le déposséder littérairement. Le conseiller fédéral conservateur Philipp Etter a joué un rôle déterminant dans ce processus. L'injustice commise à l'encontre de Spitteler et de Fränkel est toujours d'actualité. Aujourd'hui, un travail de réparation devrait être pris en charge par la germanistique et la politique
Palaeowater in coastal aquifers of Spain
No full textIn the framework of the PALAEAUX project, three coastal aquifers have been studied in Spain, looking at the possible existence of Pleistocene or Early Holocene fresh groundwater, in addition to the formerly studied Llobregat Delta. They constitute representative situations of the most common coastal aquifers. The main characteristics of these four areas are:
- The Llobregat Delta system, studied since 1965, is placed to the southwest of Barcelona (NE Mediterranean coast of the Iberian Peninsula). It is a sedimentary fluvial formation of Pleistocene to recent age, which is representative of small size coastal alluvial formations with the deep confined aquifer open to the sea offshore. Marine sea water penetrated the deep Pleistocene layer during the Flandrian sea-level rise but afterwards relatively high freshwater heads upstream allowed its progressive flushing to the sea through the submarine outlet since 6000–8000 a ago. Freshwater turnover time is shorter than the Holocene duration and it has been renovated due to natural discharge of the aquifer to the sea. The renovation process has recently been accelerated due to intensive groundwater exploitation during the past century. Nowadays, only freshwater a few centuries old remains in low permeability areas of the confined Pleistocene aquifer.
- The Doñana sedimentary aquifer system corresponds to the ancient estuary of the Guadalquivir River (SW Spain). It contains old saline groundwater that has not been flushed away due to the low freshwater head. In this aquifer 39At, 85Kr, 3H, 14C and 13C measurements have been used to ascertain the age structure of several mixed groundwater samples. After correction, the oldest fresh groundwater 14C age is c. 12–15 ka but 39Ar ages point to somewhat younger water. Neither the stable isotope contents nor the recharge temperature calculated from noble gases show a climatic signature for these waters.
- The Inca-Sa Pobla carbonate system is the northeast sector of the island of Mallorca. Brackish and salt groundwater in the coastal area has been found along the coastal strip of S’Albufera, displaying what seems a convective-like flow pattern inside the up to 200 m thick aquifer. The most consistent estimated average 14C ages of the mixed water vary between 9 and 13 ka, i.e. Early Holocene-Late Pleistocene. Water 18O and 2H contents do not show a clear climatic signature.
- The Amurga volcanic Massif is on the southeast of the island of Gran Canaria. Brackish groundwater is found in the thick phonolite rock sequence. The unsaturated zone can be up to 200 m thick. Groundwater salinity is due to recharge under arid conditions and the influence of marine airborne salts. Groundwater 14C age is possibly c. 11 ka, indicating a Late Pleistocene age water mixture. The small recharge due to aridity and the thick unsaturated zone explains this. Stable-water isotopes show no clear climatic signatur
Palaeowaters from the Glatt Valley, Switzerland
No full textIsotopic and noble gas data from a confined gravel aquifer in the Swiss Plateau has been investigated. From glaciomorphological studies it is well known that the Glatt Valley was repeatedly ice covered during the last glacial period. Corrected radiocarbon ages range from 0 to >28 ka bp and reveal a gap of between 25 and 17 ka bp, indicating an interruption of groundwater recharge during the last glacial maximum. Based on 39Ar measurements, a contribution of younger water components with residence times of a few hundred years have been identified in some waters. Recharge temperatures, estimated by analysis of noble gas contents, suggest a temperature difference of c. 5°C at the Holocene-Pleistocene transition at 12 ka bp. The long-term temporal δ18O-recharge temperature relation over the last 30 ka has a slope of c. 0.49‰ °C−1, consistent with the modern seasonal relation
Long photoperiod impairs learning in male but not female medaka
No full textDay length in conjunction with seasonal cycles affects many aspects of animal biology. We have studied photoperiod-dependent alterations of complex behavior in the teleost, medaka (Oryzias latipes), a photoperiodic breeder, in a learning paradigm whereby fish have to activate a sensor to obtain a food reward. Medaka were tested under a long (14:10 LD) and short (10:14 LD) photoperiod in three different groups: mixed-sex, all-males, and all-females. Under long photoperiod, medaka mixed-sex groups learned rapidly with a stable response. Unexpectedly, males-only groups showed a strong learning deficit, whereas females-only groups performed efficiently. In mixed-sex groups, female individuals drove group learning, whereas males apparently prioritized mating over feeding behavior resulting in strongly reduced learning performance. Under short photoperiod, where medaka do not mate, male performance improved to a level similar to that of females. Thus, photoperiod has sex-specific effects on the learning performance of a seasonal vertebrate
Protein supplements in the hog fattening ration under eastern Colorado conditions
No full textJune 2, 1932.Includes bibliographical references (pages 102-103)
- …
