A note on the dispersion pattern of marked bream Abramis brama released into Tjeukemeer, The Netherlands

Following the release of 4619 opercular tagged bream in Tjeukemeer, 101 fish were subsequently recaptured outside the lake (1969–72). The maximum distance travelled was 60 km. Although the initial dispersal of fish out of the lake appeared to be random there was some evidence of homing once fish had gained access to the IJsselmeer.     

A note on the integral-equation description of metabolizing systems

The assumptions latent in the derivation of the integral equation of Branson are rendered explicit and discussed. It is shown that the equation is valid only for systems in which the substance disappears according to a linear rate law.     

A note on Acrophylla wülfingi Redtenbacher (Insecta: Phasmida) with a description of the male

Cultures of Acrophylla wülfingi Redtenbacher in Britain were for many years mistaken for the allied Acrophylla titan Macleay. The male is described for the first time.     

Conflict between Dolphins and a Data-Scarce Fishery of the European Union

Fisheries depredation by marine mammals is an economic concern worldwide. We combined questionnaires, acoustic monitoring, and participatory experiments to investigate the occurrence of bottlenose dolphins in the fisheries of Northern Cyprus, and the extent of their conflict with set-nets, an economically important metier of Mediterranean fisheries. Dolphins were present in fishing grounds throughout the year and were detected at 28% of sets. Net damage was on average six times greater where dolphins were present, was correlated with dolphin presence, and the associated costs were considerable. An acoustic deterrent pinger was tested, but had no significant effect although more powerful pingers could have greater impact. However, our findings indicate that effective management of fish stocks is urgently required to address the overexploitation that is likely driving depredation behaviour in dolphins, that in turn leads to net damage and the associated costs to the fisheries.     

A Mathematical Model of a Fishery with Variable Market Price: Sustainable Fishery/Over-exploitation

We present a mathematical bioeconomic model of a fishery with a variable price. The model describes the time evolution of the resource, the fishing effort and the price which is assumed to vary with respect to supply and demand. The supply is the instantaneous catch while the demand function is assumed to be a monotone decreasing function of price. We show that a generic market price equation (MPE) can be derived and has to be solved to calculate non trivial equilibria of the model. This MPE can have 1, 2 or 3 equilibria. We perform the analysis of local and global stability of equilibria. The MPE is extended to two cases: an age-structured fish population and a fishery with storage of the resource.     

Factors affecting the distribution of benthic and littoral rotifers in a large marine lagoon,together with the description of a new species

Diffusion plays an important role in the exchange processes between lake sediments and the overlying water. Compounds entering the sediments usually have to penetrate through a certain mud thickness, where a reaction may then occur, while compounds being released have to diffuse through the interstitial water before escaping into the lake water.In this article mathematical functions are given which describe certain cases. They are all based on the differential diffusion equation of Fick, but for different boundary conditions different mathematical solutions of partial differential equations are needed. Four of these are presented in this paper, covering the cases of a compound diffusing into the sediments, with or without a chemical reaction occurring in the sediments, combined with either a constant or a non-constant concentration in the water.Furthermore a numerical approach is proposed in which the calculations are made by an iteration process over time and space. The results are presented as a series of concentrations as a function of time and depth in the sediment layer. It is shown in the first place that the time and the space steps must be sufficient small in agreement with the dimensions and time scale of the processes studied in order to obtain a satisfactory precision. The results can be fitted to a simplified exponential equation of the form (A · e^{–·t b} – B), which can be used for a quick assessment of special cases, depends on porosity, ratio between water and mud height; b 0.667. Furthermore this equation can be used to extrapolate from laboratory experiments with the sediments of a specific lake to results valid for the lake itself.The numerical model has also been used to describe the backward diffusion of an eventual product of a chemical reaction, which will diffuse further downward, but also upward. This is e.g. the case for the N₂O production during denitrification experiments when acetylene is applied as an inhibitor.Finally, the application of so called peepers and benthic chambers is discussed, while many of their disadvantages are explained.     

Testing association between species abundance and a continuous variable with Kolmogorov-Smirnov statistics

Association of species abundance with a continuous environmental variable is frequently tested with regression or correlation analyses. However, because these methods ignore the range and frequency distribution of levels of the variable occurring in the study area, they may generate misleading results. We give examples to illustrate the argument. A better approach to test the association between species abundance and a continuous variable should compare levels of the variable in the study area to levels of the variable occurring in sites occupied by the species. If a particular species abundance is not associated with a given continuous variable, then the frequency distribution of levels of this variable measured where individuals of the species occur should mirror the frequency distribution of levels of the variable measured over the study area. We explain how to use the one- and two-sample Kolmogorov-Smirnov statistics to compare the cumulative relative frequencies of levels of the variable where individuals are present with points in the study area. We discuss the statistics, assumptions, limitations, and advantages of these tests.     

A note on the correlation between heterozygosity and recombination rate

Mechanisms responsible for the correlation between heterozygosity and recombination rate have been thought to be background selection and selective sweep. In addition to these two, diversity enhancing selection and/or gene conversion is suggested to be contributing to the correlation, by surveying some examples of highly polymorphic loci that tend to locate in high-recombination regions.     

A note on the significance of larger bivalve molluscs (Anodonta spp. and Dreissena sp.) in the food of the eel (Anguilla anguilla) in Tjeukemeer

The stomach contents of 517 eels were analysed during 1979. In that particular year the diet consisted predominantly of chironomids, but large bivalve molluscs were of secondary importance. The meaning of this observation is discussed in relation to food conditions and the food preference of the eel.     

WRN helicase and FEN-1 form a complex upon replication arrest and together process branchmigrating DNA structures associated with the replication fork

Werner Syndrome is a premature aging disorder characterized by genomic instability, elevated recombination, and replication defects. It has been hypothesized that defective processing of certain replication fork structures by WRN may contribute to genomic instability. Fluorescence resonance energy transfer (FRET) analyses show that WRN and Flap Endonuclease-1 (FEN-1) form a complex in vivo that colocalizes in foci associated with arrested replication forks. WRN effectively stimulates FEN-1 cleavage of branch-migrating double-flap structures that are the physiological substrates of FEN-1 during replication. Biochemical analyses demonstrate that WRN helicase unwinds the chicken-foot HJ intermediate associated with a regressed replication fork and stimulates FEN-1 to cleave the unwound product in a structure-dependent manner. These results provide evidence for an interaction between WRN and FEN-1 in vivo and suggest that these proteins function together to process DNA structures associated with the replication fork.     

A re-evaluation of the Bruchiaceae with the description of a new genus

It is proposed that the Bruchiaceae be restored as a family distinct from the Dicranaceae on the basis of the longnecked, stomatose capsules. The peristome teeth, when present, are vertically barred (or papillose when reduced) rather than vertically pitted. The family is considered to consist ofBruchia, Pringleella,Eobruchia gen. nov., andTrematodon. The Bruchiaceae seem transitional between the Dicranaceae and the Ditrichaceae.Wilsoniella is transferred to the Ditrichaceae andCampylostelium venezuelanum toDicranella.     

A brief note on the study of yieldin,a wall-bound protein that regulates the yield threshold of the cell wall

Yielding of plant-cell walls is defined by the mechanical properties of walls such as their extensibility (Φ for in vivo, φ for in vitro cell wall) and yield threshold (Y for in vivo, y for in vitro cell wall). A protein named yieldin, isolated from the cell wall of growing hypocotyls of Vigna unguiculata L. (cowpea), has been demonstrated to regulate the pH dependency of y in the cell wall of the glycerinated hollow cylinder of the cowpea hypocotyl. This mini-review outlines the process of the discovery of yieldin, and also refers to the progress of studies on yieldin: the molecular cloning of yieldin and its immunolocalization in the etiolated cowpea hypocotyl. Electronic Publication     

A note upon the striatal distribution of cytochrome oxidase activity in the rat and in the cat.

The distribution of cytochrome oxidase (CO) activity was explored in the striatum of two mammalian species, the rat and the cat. Regional differences in the striatal distribution of CO were detected in both species. Thus, in most of our experimental material for rodents, an extensive band richer in CO was present in peripheral regions of the rostral and outer part of the corpus striatum. This striatal band was running in coronal sections, from medial and dorsal to lateral and ventral. In the cat's striatum, rostral and, above all, dorsal territories of the caudate nucleus were prominently stained for CO. In addition, in both species, although more sharply shown in the cat, it was possible to delineate a heterogeneous distribution of this mitochondrial enzyme following the local compartmental design of acetylcholinesterase (AChE) within the mammalian striatum. Zones with low concentration of AChE were in register with areas in which CO was low as well. This regional and local striatal heterogeneity might be a consequence of differences in the mitochondrial activity of cells located in diverse histochemical striatal parcels and, therefore, with different functional targets outside the striatum.