Induction of male production in clones of Daphnia pulex by the juvenoid hormone methyl farnesoate under short photoperiod

The juvenile hormone, methyl farnesoate (MF), and its analog insecticides have been used successfully to induce the production of males in cladocerans under long-day conditions in the laboratory. However, without hormone addition Daphnia do not usually produce male offspring under long photoperiods, while short photoperiods are a stimulus for the induction of males. We used 21 clones of Daphnia pulex differing in their propensity to produce males under short-day conditions to test whether the treatment with MF would result in an additive effect of shifting the sex ratio towards males. Contrary to our expectations, clones with a high tendency of male production showed a reduced sex ratio in response to MF treatment under short-day conditions, but clones that produced normally few males or did not produce males were stimulated by 700 nM MF to produce up to 40% males. We suggest that the endocrine disruptive effect of MF or juvenile hormone analogs in the field may depend on the clonal composition of the cladoceran population and on the natural photoperiod. This may affect the seasonal occurrence of sexual reproduction and eventually cause a mismatch between the presence of males and ephippial females

Finding the optimal vertical distribution: behavioural responses of Daphnia pulicaria to gradients of environmental factors and the presence of fish

1. The vertical distribution of zooplankton results from active habitat choice aiming to optimise fitness gain in a system of trade-offs. 2. Using large, controlled indoor mesocosms (Plo¨n Plankton Towers), we monitored the behavioural response of Daphnia pulicaria to vertical gradients of temperature, food, oxygen and light, in the presence and absence of fish predation. 3. In the absence of fish, Daphnia distributed as predicted by an ideal ‘free distribution with costs’. If the food was distributed homogeneously, they stayed in the warm epilimnion, while they balanced their time dwelling in epi- and hypolimnion if the food was concentrated in a deep-water maximum. 4. However, oxygen depletion in the hypolimnion, representing an additional cost, prevented Daphnia from completely exploiting the hypolimnetic food maximum. Consequently, the proportion dwelling in the hypolimnion was larger if oxygen was not limiting. 5. Fish predation had an overwhelming effect, driving Daphnia into the hypolimnion under all experimental conditions. If permitted by oxygen availability, Daphnia used the whole hypolimnion, but oxygen depletion reduced their possible habitat to the upper hypolimnion with oxygen concentrations above c. 0.7 mg L)1. As fish were less tolerant of low oxygen, the layer below the thermocline formed a predation refuge for Daphni

A little bit is better than nothing: the incomplete parthenogenesis of salamanders, frogs and fish

A re-examination of the mitochondrial genomes of unisexual salamander lineages, published in BMC Evolutionary Biology, shows them to be the oldest unisexual vertebrates known, having been around for 5 million years. This presents a challenge to the prediction that lack of genetic recombination is a fast track to extinction

Pleistocene occupation of the arid zone in Southeast Australia: Research prospects for the Cooper Creek-Strzelecki Desert Region

Archaeological evidence for the presence of people in southeastern Australia as early as 40,000 years ago in environments substantially different from the Southeast Asian homeland of the initial colonists of Greater Australia has generated much discussion on when and how this remarkable feat of colonisation took place, and what was the nature and pace of adjustment of the early colonists to this new continent (see for example Bowdler 1976; Jones 1979; White and O'Connell 1979). Tied in with this discussion are questions of whether there was one group of colonists or several (see Thorne 1971, 1977), and to what extent they transformed the landscape through their impact on the fauna, flora and landforming processes

Pleistocene Archaeology in the Flinders Range: Research Prospects

This research in the Flinders Range is aimed at extending northward the earlier work by Lampert (1977, 1979, forthcoming), that was directed mainly towards the prehistory of Kangaroo Island and adjacent parts of the South Australian mainland. In that region the early stone industry is known as the Kartan. Presumably Pleistocene in origin, it is characterized by a predominance of heavy core tools, while steep-edged scrapers made on flakes constitute a relatively minor element compared with early industries found elsewhere in Australia. Because of this difference, the Kartan is seen by Lampert as a regional variant of the Australian core tool and scraper tradition. Claims by Cooper (1943) for the presence of the Kartan industry at widespread sites in the Flinders Range prompted our investigation of the region

Combining Appearance and Motion for Human Action Classification in Videos

We study the question of activity classification in videos and present a novel approach for recognizing human action categories in videos by combining information from appearance and motion of human body parts. Our approach uses a tracking step which involves Particle Filtering and a local non - parametric clustering step. The motion information is provided by the trajectory of the cluster modes of a local set of particles. The statistical information about the particles of that cluster over a number of frames provides the appearance information. Later we use a “Bag ofWords” model to build one histogram per video sequence from the set of these robust appearance and motion descriptors. These histograms provide us characteristic information which helps us to discriminate among various human actions and thus classify them correctly. We tested our approach on the standard KTH and Weizmann human action datasets and the results were comparable to the state of the art. Additionally our approach is able to distinguish between activities that involve the motion of complete body from those in which only certain body parts move. In other words, our method discriminates well between activities with “gross motion” like running, jogging etc. and “local motion” like waving, boxing etc

Effect of excited states and applied magnetic fields on the measured hole mobility in an organic semiconductor

Copyright 2010 by the American Physical Society. Article is available at

Bipolar-Driven Large Magnetoresistance in Silicon

Large linear magnetoresistance (MR) in electron-injected p-type silicon at very low magnetic field is observed experimentally at room temperature. The large linear MR is induced in electron-dominated space-charge transport regime, where the magnetic field modulation of electron-to-hole density ratio controls the MR, as indicated by the magnetic field dependence of Hall coefficient in the silicon device. Contrary to the space-charge-induced MR effect in unipolar silicon device, where the large linear MR is inhomogeneity-induced, our results provide a different insight into the mechanism of large linear MR in non-magnetic semiconductors that is not based on the inhomogeneity model. This approach enables homogeneous semiconductors to exhibit large linear MR at low magnetic fields that until now has only been appearing in semiconductors with strong inhomogeneities.Comment: 23 pages, 4 figures (main text), 6 figures (supplemental material

Intravascular coagulation resulting from intravenous injection of C. parvum in mice.

In mice, i.v. C. parvum induces intravascular coagulation. This is a prolonged reaction lasting up to 7 days. It results in thrombosis in hepatic vessels with consequent hepatic necrosis, and thrombosis in pulmonary and splenic vessels. This may be important in the assessment of the tumour-inhibitory activity of C. parvum