Functional role of phenylacetic acid from metapleural gland secretions in controlling fungal pathogens in evolutionarily derived leaf-cutting ants

Fungus-farming ant colonies vary four to five orders of magnitude in size. They employ compounds from actinomycete bacteria and exocrine glands as antimicrobial agents. Atta colonies have millions of ants and are particularly relevant for understanding hygienic strategies as they have abandoned their ancestors'' prime dependence on antibiotic-based biological control in favour of using metapleural gland (MG) chemical secretions. Atta MGs are unique in synthesizing large quantities of phenylacetic acid (PAA), a known but little investigated antimicrobial agent. We show that particularly the smallest workers greatly reduce germination rates of Escovopsis and Metarhizium spores after actively applying PAA to experimental infection targets in garden fragments and transferring the spores to the ants'' infrabuccal cavities. In vitro assays further indicated that Escovopsis strains isolated from evolutionarily derived leaf-cutting ants are less sensitive to PAA than strains from phylogenetically more basal fungus-farming ants, consistent with the dynamics of an evolutionary arms race between virulence and control for Escovopsis, but not Metarhizium. Atta ants form larger colonies with more extreme caste differentiation relative to other attines, in societies characterized by an almost complete absence of reproductive conflicts. We hypothesize that these changes are associated with unique evolutionary innovations in chemical pest management that appear robust against selection pressure for resistance by specialized mycopathogens.     

Nutritional estimate of populations of some wild free-ranging African ungulates in grassland (Nechisar national park, Ethiopia) in dry season

The amount and nutritive value of forage plants, diet composition, digestibility of dry matter and nutrients were recorded for zebra. Grant's gazelle, Swayne's hartebeest and hippopotamus in November-December 1991 Besides, daily egest of feces, the level of food and nutrient consumption, energy and protein requirements were recorded for zebra and Grant's gazelle The digestibility of pasture forage was determined as a ratio of lignin concentration in food to the concentration m feces (lignin tracer technique), a daily intake was calculated on the basis of the daily feces egest Protein percentage m the diet of zebra and hartebeest consuming dry parts of grasses did not exceed 5% Gazelle diet consists of green parts of plants and included 18% of protein The digestibility of dry matter in nonruminants (zebra, hippopotamus) was 40-45%, in hartebeest - 50%, in gazelle - 60% Due to the abundance of dry grasses (3 7 ton ha^-1) the daily food consumption of zebra was high - 7 2 kg ind^-1 (dry weight), the metabolizable energy intake (ME) being 51 MJ Adult gazelles consumed 15-25 kg ind^-1 of food and 14-24 MJ of ME The energy requirements of adult males and non-lactating females of zebras and gazelles (48 and 13 MJ respectively) were met, the energy balance berig negative for lactating animals The daily protein requirement was not met in zebra (392-704 g md^-1 vs 134 g ind^-1 of intake) and in lactating gazelles (250 g ind^-1 vs 197 g md^-1) Non-lactating gazelles consume sufficient amount of both energy and protein due to the high feeding selectivity of the species and thanks to the abundance of burnt areas with young green after-grass m the dry period     

Weight management in obese pets: the tailoring concept and how it can improve results

Obesity is now recognised as the most important medical disease in pets worldwide. All current strategies for weight management involve dietary energy restriction with a purpose-formulated diet. Whilst current weight management regimes can be successful, outcomes are often disappointing with the rate of weight loss progressively slowing down as time goes on. Success is most challenging for the most obese dogs and cats that are more likely to discontinue the programme before reaching target weight. To improve outcomes, clinicians must focus carefully on better tailoring programmes, paying particular to setting an appropriate target weight so as to maximise the benefits for the individual. In this opinionated review, the author will discuss findings from recent clinical research studies examining weight management in obese dogs and cats. A strategy for tailoring weight management targets will then be discussed, illustrated with case examples.

     

Demographic population structure of black howler monkeys in fragmented and continuous forest in Chiapas,Mexico: Implications for conservation

For wild primates, demography studies are increasingly recognized as necessary for assessing the viability of vulnerable populations experiencing rapid environmental change. In particular, anthropogenic changes such as habitat loss and fragmentation can cause ecological and behavioral changes in small, isolated populations, which may, over time, alter population density and demographic structure (age/sex classes and group composition) in fragment populations relative to continuous forest populations. We compared our study population of Endangered black howler monkeys (Alouatta pigra) in 34 forest fragments around Palenque National Park (PNP), Mexico (62 groups, 407 individuals), to the adjacent population in PNP, protected primary forest (21 groups, 134 individuals), and to previous research on black howlers in fragments in our study area (18 groups, 115 individuals). We used χ² and Mann–Whitney U tests to address the questions: (a) what is the current black howler demographic population structure in unprotected forest fragments around PNP? (b) How does it compare to PNP's stable, continuous population? (c) How has it changed over time? Compared to the PNP population, the fragment populations showed higher density, a significantly lower proportion of multimale groups, and significantly fewer adult males per group. The population's age/sex structure in the fragmented landscape has been stable over the last 17 years, but differed in a higher proportion of multifemale groups, higher density, and higher patch occupancy in the present. In the context of conservation, some of our results may be positive as they indicate possible population growth over time. However, long-term scarcity of adult males in fragments and associated effects on population demographic structure might be cause for concern, in that it may affect gene flow and genetic diversity. The scarcity of adult males might stem from males experiencing increased mortality while dispersing in the fragmented landscape, whereas females might be becoming more philopatric in fragments.     

Increased amounts of hybrid (heavy/heavy) DNA in Bloom's syndrome fibroblasts

The nuclear DNA of fibroblasts from patients suffering with Bloom's syndrome, density labeled for less than one round of DNA replication to give heavy/light molecules, was examined for spontaneous amounts of heavy/heavy DNA (hybrid DNA). When compared to normal fibroblasts the Bloom's syndrome cells exhibited a sixfold increase in such DNA.     

Studien zur speziellen Systematik derPirolaceae

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