Entamoeba histolytica: Collagenolytic Activity and Virulence1

Several axenic strains of pathogenic and nonpathogenic Entamoeba histolytica were tested for their capacity to digest native radioactive type I collagen gels and to produce liver abscesses when injected into the liver of newborn hamsters. The results demonstrate that the pathogenic strains of amebas (HM1:IMSS, HM3:IMSS, HM38:IMSS, and HK9) have a collagenolytic activity that closely correlates with their in vivo capacity to produce liver lesions. The nonpathogenic isolate (Laredo) did not show collagenolytic activity and failed to produce lesions in the liver of newborn hamsters. The results also demonstrate that type I collagen obtained from rodents and cats is degraded less by amebic collagenase than is bovine collagen, which is similar to human collagen. These findings suggest that species susceptibility to invasive infection may depend, among other factors, on the characteristics of the extracellular components of host tissues.     

The K+/H+ antiporter LeNHX2 increases salt tolerance by improving K+ homeostasis in transgenic tomato

The endosomal LeNHX2 ion transporter exchanges H⁺ with K⁺ and, to lesser extent, Na⁺. Here, we investigated the response to NaCl supply and K⁺ deprivation in transgenic tomato (Solanum lycopersicum L.) overexpressing LeNHX2 and show that transformed tomato plants grew better in saline conditions than untransformed controls, whereas in the absence of K⁺ the opposite was found. Analysis of mineral composition showed a higher K⁺ content in roots, shoots and xylem sap of transgenic plants and no differences in Na⁺ content between transgenic and untransformed plants grown either in the presence or the absence of 120 mm NaCl. Transgenic plants showed higher Na⁺/H⁺ and, above all, K⁺/H⁺ transport activity in root intracellular membrane vesicles. Under K⁺ limiting conditions, transgenic plants enhanced root expression of the high‐affinity K⁺ uptake system HAK5 compared to untransformed controls. Furthermore, tomato overexpressing LeNHX2 showed twofold higher K⁺ depletion rates and half cytosolic K⁺ activity than untransformed controls. Under NaCl stress, transgenic plants showed higher uptake velocity for K⁺ and lower cytosolic K⁺ activity than untransformed plants. These results indicate the fundamental role of K⁺ homeostasis in the better performance of LeNHX2 overexpressing tomato under NaCl stress.     

Cross‐amplification of 10 new isolated polymorphic microsatellite loci for red mullet (Mullus barbatus) in striped red mullet (Mullus surmuletus)

Ten polymorphic dinucleotide microsatellite loci were isolated and characterized for the red mullet (Mullus barbatus). Allele variability was tested on both the red mullet and its congener the striped red mullet (Mullus surmuletus). Characterization of 30 individuals of both species from the western Mediterranean showed moderate to high allelic diversity ranging from two to 26 alleles per locus (mean 10.9). Three loci showed departures from Hardy–Weinberg proportions. No evidence of significant association between genotypes at pairs of loci was observed. These polymorphic loci could be suitable for population genetic assessments of both species.     

Assortative mating among rock-dwelling cichlid fishes supports high estimates of species richness from Lake Malawi

It has been estimated that Lake Malawi, Africa, contains 500–650 endemic species of cichlid fishes, the largest number of vertebrate species endemic to any comparable sized area on the planet. As many of these putative species cannot be distinguished anatomically, these estimates of species richness depend to a great extent on the assumption that sympatrically occurring male colour morphs represent biological species. We have tested this assumption using a combination of behavioural observations of courtship and microsatellite DNA analysis for six putative species of the Pseudotropheus ( Tropheops ) complex and three of the Pseudotropheus ( Maylandia ) complex occurring sympatrically at Nkhata Bay. We were unable to demonstrate assortative courtship for the species pairs Pseudotropheus ( Maylandia ) zebra / P . 'gold zebra' or P. ( Tropheops ) 'band'/ P. ( T .) 'rust' because we were unable to distinguish between the females of these taxa. All other taxa showed clear assortative courtship, except for P. ( T .) 'deep', a deep-water species which was rarely observed. Fixation indices (θ_ST for the infinite allele model, and R _ST for the stepwise mutation model) calculated from six microsatellite DNA loci demonstrated significant deviations from panmixia in all pairwise comparisons of putative species, indicating little or no gene flow between populations. All taxa showed high levels of allelic diversity providing evidence that genetic bottlenecking may have been of limited importance in the speciation process. Assortative mating among taxa differing only in male colouration is supportive of theories that speciation in these fishes has been driven by sexual selection by female choice.     

Burrowing Owl Mortality in the Altamont Pass Wind Resource Area

Abstract: We estimated wind turbines in the Altamont Pass Wind Resource Area (APWRA), California, USA, kill >100 burrowing owls (Athene cunicularia hypugaea) annually, or about the same number likely nesting in the APWRA. Turbine-caused mortality was up to 12 times greater in areas of rodent control, where flights close to the rotor plane were disproportionately more common and fatalities twice as frequent as expected. Mortality was highest during January through March. Burrowing owls flew within 50 m of turbines about 10 times longer than expected, and they flew close to wind turbines disproportionately longer within the sparsest turbine fields, by turbines on tubular towers, at the edges of gaps in the turbine row, in canyons, and at lower elevations. They perched, flew close to operating turbine blades, and collided disproportionately more often at turbines with the most cattle dung within 20 m, with the highest densities of ground squirrel (Spermophilus beecheyi) burrow systems within 15 m, and with burrowing owl burrows located within 90 m of turbines. A model of relative collision threat predicted 29% of the 4,074 turbines in our sample to be more dangerous, and these killed 71% of the burrowing owls in our sample. This model can help select the most dangerous turbines for shutdown or relocation. All turbines in the APWRA could be shut down and blades locked during winter, when 35% of the burrowing owls were killed but only 14% of the annual electricity was generated. Terminating rodent control and installing flight diverters at the ends of turbine rows might also reduce burrowing owl mortality, as might replacing turbines with new-generation turbines mounted on taller towers.     

Reassessing the Odontites purpureus group (Orobanchaceae) from south‐east Spain and north‐west Africa

We describe a species of Odontites, O. bolligeri E.Rico, L.Delgado & Herrero, endemic to the south‐eastern Iberian Peninsula and north Africa, from Morocco to Tunisia. This species belongs to the O. purpureus group and corresponds to the taxon that the monographer Markus Bolliger called O. squarrosus subsp. squarrosus. However, according to the International Code of Botanical Nomenclature (ICBN), this is an invalid name, and hence we propose a new name for these plants here. Drawings of the new species are also supplied. In addition, we compare and discuss the other species of the O. purpureus group, propose a key for them and include a karyological study of the two Iberian species of the group. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 701–708.     

Effects of starvation and sucrose feeding on corpora allata of last instar larvae of Manduca sexta: in vitro activity, size, and cell number

Abstract Larvae of the tobacco hornworm moth Manduca sexta starved for the first 3 days of the last (fifth) stadium undergo a supernumerary moult. If they are provided with sucrose during the starvation period, they develop into normal pupae although pupation is delayed. The activities of the corpora allata (CA) from normal, starved, and sucrose fed larvae were followed through the fifth stadium with a radiochemical assay for Juvenile Hormone (JH) biosynthesis. An attempt was made to correlate CA-activity with CA cell number, size, and protein content.
In CA of normally fed larvae the rate of JH synthesis declined to undetectable levels by day 4 which was also the time of exposure of the dorsal vessel. In CA of starved larvae, the rate of JH synthesis at first decreased but began to increase on day 3 and reached a peak value by day 7 , at which time head capsule slippage occurred. In CA of sucrose fed larvae, the rate of biosynthesis declined as in normal larvae but the decline was extended over a longer period. Exposure of the dorsal vessel was delayed in the same manner and occurred on days 7–9. The major JH in all cases was JH-II.
The CA comprise c. 150 cells in the early fifth stadium, and this number remained constant during the fifth stadium in all three feeding regimens. In normal larvae, CA size and protein content increased several-fold during the stadium whereas in starved and sucrose-fed larvae they increased slowly and in agreement with the altered timing of developmental events. In none of the groups was the CA activity pattern correlated with morphometric changes of the CA. The rates of JH biosynthesis were not closely correlated with published JH titre curves. The in vivo mechanisms for regulation of JH production remain to be elucidated.     

Karyosystematic study of Potentilla L. subgen. Potentilla (Rosaceae) in the Iberian Peninsula

Chromosome numbers in 80 populations belonging to 18 species of Potentilla L. subgen. Potentilla from the Iberian Peninsula and two of P. maura, a North African endemic taxon, have been counted. The basic number of chromosomes is always x = 7 and these chromosomes are small (between 1 and 2 μm). For three species, the number of chromosomes is reported for the first time and, for another six, this number has been established in Iberian representatives. Moreover, new ploidy levels have been obtained for P. hispanica and P. crantzii with regard to their entire distribution area, and in P. cinerea and P. neumanniana for the Iberian Peninsula. Some taxonomic, phylogenetic and phytogeographic comments are made for several species or groups of species from the West Mediterranean region. In 13 species only one ploidy level has been found, but six species have several ploidy levels. Seven ploidy levels occur in the investigated taxa. The frequency of each ploidy level represented within Iberian Potentilla is analysed and the data are compared with those available for taxa from the rest of the distribution area of the genus.     

The male postabdomen and reproductive system of Bibio marci Linnaeus, 1758 (Hexapoda: Diptera: Bibionidae)

The male postabdomen and the internal parts of the male genital system of Bibio marci (Bibionomorpha) were examined and reconstructed 3‐dimensionally. Several features differ from the presumptive dipteran groundplan. The bases of the gonopods are fused with each other and with tergite IX. The penis is not tube‐shaped and only sclerotized on the ventral side. The vasa deferentia are S‐shaped, and two pairs of accessory glands are present. In contrast to these characteristics, the arrangement of the internal parts is probably close to the ancestral condition. With its specific shape, the penis is well suited for the transfer of a spermatophore. The dorsal sclerite of the copulatory organ probably represents the medially fused parameres. A cladistic analysis of 27 characters of the postabdomen yielded two most parsimonious trees, with the strict consensus as follows: Nannochoristidae (outgroup) + (Culicidae [Culicomorpha] + ((Nymphomyiidae + (Tipulidae + Trichoceridae)) + (Tabanidae [Brachycera] + (Bibionidae, Anisopodidae, Axymyiidae [Bibionomorpha])))). Potential synapomorphies of Bibionomorpha (including Axymyiidae) and Brachycera are the fusion of sternum IX with the gonocoxites, the fusion of the parameres forming the dorsal sclerite and the presence of an entire series of postabdominal muscles (M4, M20, M23, M26, M27, M31, M35 and M37). The results of the analysis are preliminary as it is based on a single‐character system with a limited taxon sampling. However, the main result – a clade Bibionomorpha + Brachycera – is fully compatible with current hypotheses on dipteran phylogeny.