Are landscape complexity and farm specialisation related to land-use intensity of annual crop fields?

Little is known about the predictive value of landscape complexity and farm specialisation for land-use intensity, although this is critical for regional agri–environmental schemes and conservation of biodiversity. Here, we analysed land-use intensity of annual crop fields of 30 farms in northern Germany that were located in 15 landscapes differing in structural complexity ranging from <15% to >65% non-crop habitats. The proportion of arable land per landscape was used as simple predictor of landscape complexity due to its close correlation with habitat-type diversity, and the proportion of arable land per farm acted as an indicator for farm specialisation due to its negative correlation with stock farming. Land-use intensity was quantified using questionnaires. Landscape complexity and farm specialisation were related to several but not all indicators of land-use intensity. Structurally simple landscapes were related to more nitrogen input and higher crop yields, and farms specialised on annual crops had reduced crop-species diversity, larger fields, higher crop yields and more pathogen species. In contrast to general expectations, pesticide use in annual crop fields was exceptionally high and not a function of landscape complexity or farm specialisation. Our results show that generalisations such as “farms specialised on annual crops and structurally simple landscapes show increased land-use intensity” may be misleading.     

Salinity discrimination in harbour seals: a sensory basis for spatial orientation in the marine environment?

 Salinity variations can be considered as a potential source of information for orientation in the marine environment. To use this kind of environmental information marine animals must be able to detect these salinity differences. Therefore we determined salinity-difference thresholds of two harbour seals for the discrimination of seawater solutions as a function of the salinity level (15–35‰) and compared them with the thresholds of human subjects. Whereas in humans thresholds increased with increasing salinity level, thresholds of seals decreased with increasing salinity level. Both seals achieved best sensitivity at 30‰ salinity, where they detected a salinity difference ≤4%. These data indicate that the ability of seals to detect salinity differences of seawater is well tuned to the natural occurrence of this environmental information. Their high gustatory resolving power for differences in seawater salinity is suggested to meet the basic requirements for chemosensory orientation of seals in the marine habitat. Received: 10 February 2000 / Accepted in revised form: 19 September 2000     

Prenatal diagnosis of a true mosaic trisomy 20 substantiated by demonstration of a gene dosage effect for adenosine deaminase (ADA)

Fibroblasts from a fetus with the prenatal diagnosis of mosaic trisomy 20 were cloned by dilution plating. Adenosine deaminase (ADA), a biochemical marker for chromosome 20, was assayed in trisomic clones and normal clones as control. The cytogenetic diagnosis was substantiated by demonstration of a triplex gene dosage effect for ADA in the trisomic cells.     

Introduction of early amniocentesis to routine prenatal diagnosis

With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria ‘number of colonies’ and ‘culture duration until harvest’, early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis.     

Optical Imaging of Odor-Evoked Glomerular Activity Patterns in the Antennal Lobes of the Ant Camponotus rufipes

 Ants have a well developed olfactory sense, which they need both for the perception of environmental chemicals, and for a highly sophisticated intraspecific communication system based on pheromones. The question arises therefore as to how different odors are coded in the antennal lobe, the first central neuropil to process olfactory information. We measured odor-evoked activity patterns using in vivo neuropil calcium recording in the antennal lobe of the ant Camponotus rufipes. We found that (a) odors elicit focal activity spots (diameter ca. 20 μm) which most probably represent the olfactory glomeruli; (b) different odors are coded in odor specific patterns of such activated spots, and a particular spot can participate in the pattern for different odors; (c) calcium increased in the activated spots within the 2-s stimulation period and slowly declined thereafter. Received: 10 March 1999 / Accepted in revised form: 5 July 1999     

Pattern Formation in Hydrozoa

Hydra   is famous for its ability to regenerate missing structures. Even aggregates of single cells transform eventually into normally shaped animals. This indicates a communication within the tissue and within the aggregates which determines the spatial pattern of gene expression. Such pattern-forming systems are thought to play a decisive role in the control of self-organization during embryogenesis. Marine and fresh water hydrozoa appear to allow an access to such a system. Although the molecular components are still mostly unknown, the regulatory properties of the pattern-forming system are increasingly well understood, and this may help eventually to identify the components involved.     

The evolutionary position of turtles revised

Consensus on the evolutionary position of turtles within the amniote phylogeny has eluded evolutionary biologists for more than a century. This phylogenetic problem has remained unsolved partly because turtles have such a unique morphology that only few characters can be used to link them with any other group of amniotes. Among the many alternative hypotheses that have been postulated to explain the origin and phylogenetic relationships of turtles, a general agreement among paleontologists emerged in favoring the placement of turtles as the only living survivors of the anapsid reptiles (those that lack temporal fenestrae in the skull). However, recent morphological and molecular studies have radically changed our view of amniote phylogenetic relationships, and evidence is accumulating that supports the diapsid affinities of turtles. Molecular studies favor archosaurs (crocodiles and birds) as the living sister group of turtles, whereas morphological studies support lepidosaurs (tuatara, lizards, and snakes) as the closest living relatives of turtles. Accepting these hypotheses implies that turtles cannot be viewed any longer as primitive reptiles, and that they might have lost the temporal holes in the skull secondarily rather than never having had them.