Occurrence of Halococcus spp. in the nostrils salt glands of the seabird Calonectris diomedea

The nostrils of the seabird Calonectris diomedea are endowed with a salt-excreting gland that could produce a suitable environment for the colonization of extreme halophilic prokaryotes. We have studied in this organ the presence of extreme halophiles by means of culturing techniques. We could easily cultivate members of haloarchaea, and all cultures studied were identified as members of one of the two species Halococcus morrhuae and Hcc. dombrowskii. In order to reveal the diversity of these colonizers, we undertook a taxonomic study. Altogether, the results indicated that members of the genus Halococcus may constitute a part of the natural epizootic microbiota of C. diomedea, and that they exhibit such an important degree of taxonomic variability that appeals for a pragmatic species definition. This seabird nests in the west Mediterranean coasts, but its migratory habits, reaching locations as distant from the Mediterranean as the South Atlantic, may help in the dispersal mechanisms of haloarchaea through the Earth’s surface.     

Factors affecting <Emphasis Type="Italic">Sarcocystis</Emphasis> infection of rats on small tropical islands

The purpose of our research was to explore the limits of rat-python-Sarcocystis distribution among rats on the offshore tropical islands of Singapore, and to examine the effect of island size, insular isolation, landscape peculiarities and anthropogenic disturbance. Commensal rats (Rattus rattus) inhabited all of these islands, regardless of the islands size, proximity to the mainland, biogeographic features, and/or degree of anthropogenic interference. Rats caught on Sakijang Pelepah Island had well deliminated white bellies that are similar to those of sylvatic or feral rats. The prevalence of Sarcocystis spp. on individual islands ranged from 57 to 100%. This is consistent with the range found in forested habitats on Singapore Island. It also exhibited a similar diversity to Sarcocystis spp. and the predominance of Sarcocystis singaporensis. On Sakijang Pelepah Island, one rat (white bellied) was exceptionally heavily infected with both Sarcocystis villivilosi and Sarcocystis sulawesiensis. The muscles of the rats from nearly all of the islands contained immature sarcocysts, which implies that active transmission is taking place on these islands. This suggests that reticulated pythons (Python reticulatus), which are the definitive hosts of rat Sarcocystis, might have been established or frequented in all the islands of Singapore. Our study shows that the Sarcocystis infection load of the rats was negatively correlated with human disturbance, hinting that human disturbance restricts the pythons mobility and thus, reduces infection of Sarcocytis in the islands rats.     

Denning behaviour of ship rats (Rattus rattus) on Taukihepa,a seabird breeding island

Abstract

Den sites of 14 ship rats (Rattus rattus) were located daily during the rat breeding season on Taukihepa (Big South Cape), a seabird island southwest of Rakiura (Stewart Island). In contrast to other New Zealand studies, no arboreal dens were found. Den sites on Taukihepa were in ferns, under logs, in woodpiles, or underground in sooty shearwater (Puffinusgriseus) breeding burrows. The number of times known den sites used was positively related to the amount of leaf litter and woodpiles near the den sites. Overall, 24% of radio‐tagged rats were sharing den sites on any given day. While there was considerable individual variation in the number of times den sites were used, female rats tended to reuse den sites more than males. Many rats were found in dens alone, but frequently males and females shared. Occasionally two females and one male denned together, as did two females, whereas males never denned with another male.     

Local factors associated with on‐host flea distributions on prairie dog colonies

Outbreaks of plague, a flea‐vectored bacterial disease, occur periodically in prairie dog populations in the western United States. In order to understand the conditions that are conducive to plague outbreaks and potentially predict spatial and temporal variations in risk, it is important to understand the factors associated with flea abundance and distribution that may lead to plague outbreaks. We collected and identified 20,041 fleas from 6,542 individual prairie dogs of four different species over a 4‐year period along a latitudinal gradient from Texas to Montana. We assessed local climate and other factors associated with flea prevalence and abundance, as well as the incidence of plague outbreaks. Oropsylla hirsuta, a prairie dog specialist flea, and Pulex simulans, a generalist flea species, were the most common fleas found on our pairs. High elevation pairs in Wyoming and Utah had distinct flea communities compared with the rest of the study pairs. The incidence of prairie dogs with Yersinia pestis detections in fleas was low (n = 64 prairie dogs with positive fleas out of 5,024 samples from 4,218 individual prairie dogs). The results of our regression models indicate that many factors are associated with the presence of fleas. In general, flea abundance (number of fleas on hosts) is higher during plague outbreaks, lower when prairie dogs are more abundant, and reaches peak levels when climate and weather variables are at intermediate levels. Changing climate conditions will likely affect aspects of both flea and host communities, including population densities and species composition, which may lead to changes in plague dynamics. Our results support the hypothesis that local conditions, including host, vector, and environmental factors, influence the likelihood of plague outbreaks, and that predicting changes to plague dynamics under climate change scenarios will have to consider both host and vector responses to local factors.     

Impacts of the invasive exotic <Emphasis Type="Italic">Prosopis juliflora</Emphasis> (Sw.) D.C. on the native flora and soils of the UAE

The effects of the invasive exotic Prosopis juliflora shrubs on the natural plant communities and soil chemical characters were assessed in two regions of the United Arab Emirates (UAE). Five sites were selected subjectively: three in Sharja with 73 stands and two in Ras Al-Khima with 37 stands. Stands were located randomly within each site to cover density variation in Sharja and size variation in Ras Al-Khima. Density, frequency, richness and evenness of the associated annual and perennial species were studied in nine quadrats distributed under, at the margin and outside the canopy of a P. juliflora shrub located in the center of each stand. The results indicated that the effect of P. juliflora on the associated flora depends significantly on the density and size of the canopy. Larger individuals and greater densities have significantly greater negative impacts on the associated plants. All the studied community attributes were significantly lower under P. juliflora canopies than outside. Annuals were inhibited more than perennials. The number of annuals with significant reductions in density and/or frequency under P. juliflora canopies was significantly greater than the number of perennials. Density of more than 50% of the associated annuals was significantly inhibited under P. juliflora canopies. Density of P. juliflora seedlings was greater underneath the canopy of the same species than away from them, indicating little or no self allelopathic effect (auto-inhibition) under field conditions. P. juliflora ameliorated some soil characters, through significant pH reduction and increase in K, N and P and organic matters. Hence, plant diversity might be enhanced following eradication of P. juliflora.     

Feeding strategy of the sacoglossan opisthobranch <Emphasis Type=Italic>Oxynoe olivacea</Emphasis> on the tropical green alga <Emphasis Type=Italic>Caulerpa taxifolia</Emphasis>

The feeding behaviour of the shelled sacoglossan Oxynoe olivacea was investigated to better understand the role and importance of this species in influencing encroachments of the alien alga Caulerpa taxifolia in the Mediterranean sea. We tested whether this slug preferred, as preliminary field observations suggested, an aggregative feeding behaviour and which part of the algal thallus, phylloid vs rhizoid, it preferred. Results showed that O. olivacea fed in groups and actively selected phylloid. This outcome poses important questions regarding the possibility that this species, fragmenting the alga thallus, could enhance dispersion and regeneration of C. taxifolia.     

Plant‐derived differences in the composition of aphid honeydew and their effects on colonies of aphid‐tending ants

In plant–ant–hemipteran interactions, ants visit plants to consume the honeydew produced by phloem‐feeding hemipterans. If genetically based differences in plant phloem chemistry change the chemical composition of hemipteran honeydew, then the plant's genetic constitution could have indirect effects on ants via the hemipterans. If such effects change ant behavior, they could feed back to affect the plant itself. We compared the chemical composition of honeydews produced by Aphis nerii aphid clones on two milkweed congeners, Asclepias curassavica and Asclepias incarnata, and we measured the responses of experimental Linepithema humile ant colonies to these honeydews. The compositions of secondary metabolites, sugars, and amino acids differed significantly in the honeydews from the two plant species. Ant colonies feeding on honeydew derived from A. incarnata recruited in higher numbers to artificial diet, maintained higher queen and worker dry weight, and sustained marginally more workers than ants feeding on honeydew derived from A. curassavica. Ants feeding on honeydew from A. incarnata were also more exploratory in behavioral assays than ants feeding from A. curassavica. Despite performing better when feeding on the A. incarnata honeydew, ant workers marginally preferred honeydew from A. curassavica to honeydew from A. incarnata when given a choice. Our results demonstrate that plant congeners can exert strong indirect effects on ant colonies by means of plant‐species‐specific differences in aphid honeydew chemistry. Moreover, these effects changed ant behavior and thus could feed back to affect plant performance in the field.     

Cattle ticks of the genera <Emphasis Type="Italic">Rhipicephalus</Emphasis> and <Emphasis Type="Italic">Amblyomma</Emphasis> of economic importance in Tanzania: distribution assessed with GIS based on an extensive field survey

In order to implement a robust integrated tick and tick-borne disease control programme in Tanzania, based on ecological and epidemiological knowledge of ticks and their associated diseases, a national tick and sero-surveillance study was carried out in all 21 regions of the mainland, as well as on Mafia Island, between 1998 and 2001. The current distributions of Rhipicephalus appendiculatus, R. pravus, Amblyomma variegatum, A. gemma, and A. lepidum are illustrated and discussed. Tick distribution maps were assessed using the Weights-of-Evidence method (WofE), and employing temperature, humidity, NDVI, rainfall, and land-cover predictive data. Ground-truthing was done to check correspondence both of the data employed in prediction with land-cover characteristics discerned in the field as well as of the surveyed and predicted tick distributions. Statistical methods were used to analyse associations of the tick species with their environment, cattle density, and other ticks. Except for R. appendiculatus, no appreciable changes were demonstrated in the predicted and observed tick distributions compared to the existing maps that originated in the 1950–1960s. Cattle density influenced the distribution of A. variegatum and, to a certain extent, of A. lepidum, but had no appreciable influence on the distribution of any of the other ticks discussed in this paper, neither did livestock movement. Distinct differences for environmental requirements where observed between different tick species within the same genus. The predictive maps of R. appendiculatus and R. pravus suggest their mutually exclusive distribution in Tanzania, and simultaneous statistical analysis showed R. pravus as a greater specialist. Of the three Amblyomma species, A. variegatum is the most catholic tick species in Tanzania, while both A. gemma and A. lepidum belong to the more specialized species. Despite dissimilar habitat preferences, all three Amblyomma spp. co-exist in central Tanzania, where very heterogeneous habitats may simultaneously satisfy the environmental requirements of all three species. The current study, conducted about 4 decades after the last major survey activities, has shown that changing livestock policies, unrestricted livestock movement and a continuous change in climatic/environmental conditions in Tanzania have brought about only limited changes in the distribution patterns of R. appendiculatus, R. pravus and the three Amblyomma species investigated. Whether this observation indicates a relative indifference of these ticks to environmental and/or climate changes allows room for speculation.     

Diversity of the <Emphasis Type="Italic">Fusarium</Emphasis> species associated with head and seedling blight on wheat in Slovakia

Species associated with Fusarium head blight are depending on the production and edaphic conditions. The differences are found in the representation of various Fusarium spp. in the diseases, which sporadically occur all over the territory of Slovakia, in all agricultural production types. We identified fifteen Fusarium species during ten years of investigation. Most of the mentioned species F. culmorum (W.G. Smith) Sacc., F. graminearum Schwabe, recently F. cerealis (Cooke) Sacc. (crookwellense Burgess, Nelson & Tousson) and F. sambucinum Fuckel in diseased caryopsis are seed transmitted. The significant differences among species and intra species in cultural and pathogenicity assays in vitro and in vivo were correlated. Some of them are able to produce toxic metabolites — deoxynivalenone, which probably play a role in the aggressiveness of the pathogen and promote disease development and pathogen colonization.