Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Territorial damselflies do not show immunological priming in the wild

Adaptive immunity allows vertebrates to gain protection against repeated pathogenic infections. Analogous responses (priming) have been recently uncovered in invertebrates. However, whether such responses are widespread is not known. The present study investigated the presence of immunological priming in males of a species whose phylogenetic position places it in one of the less derived insect orders. It is hypothesized that the efficiency of such a response could be related to animal condition, as assessed by the expression of a sexually selected ornament. Hetaerina americana Fabricius (Odonata: Calopterygidae) males bear a conspicuous ornament (a red wing spot), which is evolutionarily maintained via male territorial competition. Using field‐collected animals, a group of males is challenged with bacteria before exposure to a higher dose of the same or a different bacteria, and survival is compared with that of infected males not previously challenged, as well as control groups. Gram‐positive and Gram‐negative bacteria are used. To explore how long priming may take to work, the second exposure is carried out either after 1 or 5 days. Red spot and body size are entered in the analysis as predictors of survival within and between groups. There is no difference in survival among groups, which suggests no priming effect. Overall, red spot and body size are not consistent in explaining survival.     

Assessing effects of flow alteration on macroinvertebrate assemblages in Australian dryland rivers

1. Possible impacts of water‐resource development on assemblages of freshwater macroinvertebrates were investigated in the upper Darling River and some of its tributaries in north‐western New South Wales (Australia), an arid and semi‐arid region of low relief where alteration of river flows has intensified through expansion of irrigated agriculture. 2. Study sites were grouped into four hydrological regimes resulting from impoundment, flow regulation, water abstraction and natural variation, namely (i) intermittent flow with relatively little hydrological alteration from water‐resource development, (ii) intermittent flow with substantial alteration, (iii) near‐perennial flow with substantial alteration but unimpounded and (iv) near‐perennial flow with substantial alteration plus impoundment by weirs that stabilise water levels. 3. Macroinvertebrates were sampled with three methods (a quantitative cylinder sampler, handnet sampling and baited traps) in three periods with differing hydrology (recessional low flow in June 2003, high flow in March 2004 and increasing flow after drought in December 2004). 4. Taxonomic richness, assemblage composition and catch per unit effort of the crayfish Cherax destructor differed significantly among the site groups, but total macroinvertebrate density and the AUSRIVAS O/E (Australian River Assessment System observed‐over‐expected) index did not. The principal spatial differences were between the intermittent and near‐perennial rivers, and apparent effects of water‐resource development and impoundment were more subtle. Temporal differences in richness, abundance and composition were substantial and appeared to be related mainly to variations in discharge and temperature. 5. Current macroinvertebrate‐based methods for assessing the ‘condition’ or ‘health’ of Australian dryland rivers are inadequate. Such assessments might be improved with (i) reference data that take adequate account of antecedent hydrological conditions, (ii) consideration of long‐term taxonomic richness as well as richness on individual sampling occasions, (iii) evaluation of invertebrate population sizes, (iv) analysis of assemblage data by trait composition and (v) adoption of the genus as the default level of taxonomic resolution.     

Potential causes and life-history consequences of sexual size dimorphism in mammals

1. Male-biased sexual size dimorphism (SSD) in mammals has been explained by sexual selection favouring large, competitive males. However, new research has identified other potential factors leading to SSD. The aim of this review is to evaluate current research on the causes of SSD in mammals and to investigate some consequences of SSD, including costs to the larger sex and sexual segregation. 2. While larger males appear to gain reproductive benefits from their size, studies have also identified alternative mating strategies, unexpected variance in mating success and found no clear relationship between degree of polygyny and dimorphism. This implies that sexual selection is unlikely to be the single selective force directing SSD. 3. Latitude seems to influence SSD primarily through variation in overall body size and seasonal food availability, which affect potential for polygyny. Likewise, population density influences resource availability and evidence suggests that food scarcity differentially constrains the growth of the sexes. Diverging growth patterns between the sexes appear to be the primary physiological mechanism leading to SSD. 4. Female-biased dimorphism is most adequately explained by reduced male–male competition resulting in a decrease in male size. Female–female competition for dominance and resources, including mates, may also select for increased female size. 5. Most studies found that sexual segregation arises through asynchrony of activity budgets between the sexes. The larger sex can suffer sex-biased mortality through increased parasite load, selective predation and the difficulty associated with sustaining a larger body size under conditions of resource scarcity. 6. None of the variables considered here appears to contribute a disproportionate amount to SSD in mammals. Several promising avenues of research are currently overlooked and long-term studies, which have previously been biased toward ungulates, should be carried out on a variety of taxa.     

THE SPREAD OF DISEASES CAUSED BY SPECIES OF VERTICILLIUM

An investigation has been made of the spread of Verticillium disease of tomato and antirrhinum by root contact between diseased and healthy plants, and by the growth of the fungi through the soil. V. alboatrum and V. Dahliae spread rapidly by root contact, while V. tricorpus, V. nigrescens and V. nubilum showed no appreciable spread. Where the tomato and antirrhinum hosts wilted and died the causal organism was invariably isolated from the soil near the roots of the dead plants, but where the inoculated host harboured species without showing disease symptoms, as in the case of V. tricorpus and V. nubilum in antirrhinum, the parasite was never obtained from the soil. Moreover, these species in antirrhinum, and V. nigrescens and V. nubilum in tomato would appear to be mild pathogens since when they were already well established V. alboatrum was later actually found to enter and parasitize the respective hosts and bring about its own typical disease symptoms.
Spread through the soil in the absence of hosts was tested by the insertion into it of infected wheat grains followed by later attempts to isolate the fungi at varying distances from the point of infection. V. alboatrum, V. Dahliae and V. tricorpus showed little or no growth through the soil, whereas V. nigrescens and V. nubilum spread saprophytically to some extent, though never attaining sufficient concentration to cause appreciable infection of later planted tomatoes.
The conclusion is reached that spread of disease caused by species of Verticillium takes place mainly by root contact, with a rapidity relatively proportional to that of the death of the host. This finding, together with the lack of spread from antirrhinum plants infected with the non-lethal V. tricorpus and V. nubilum , suggests that the parasites remain in the vascular tracts until the death of the hosts.