Excretion patterns of coccidian oocysts and nematode eggs during the reproductive season in Northern Bald Ibis (Geronticus eremita)

Individual reproductive success largely depends on the ability to optimize behaviour, immune function and the physiological stress response. We have investigated correlations between behaviour, faecal steroid metabolites, immune parameters, parasite excretion patterns and reproductive output in a critically endangered avian species, the Northern Bald Ibis (Geronticus eremita). In particular, we related haematocrit, heterophil/lymphocyte ratio, excreted immune-reactive corticosterone metabolites and social behaviour with parasite excretion and two individual fitness parameters, namely, number of eggs laid and number of fledglings. We found that the frequency of excretion of parasites’ oocysts and eggs tended to increase with ambient temperature. Paired individuals excreted significantly more samples containing nematode eggs than unpaired ones. The excretion of nematode eggs was also significantly more frequent in females than in males. Individuals with a high proportion of droppings containing coccidian oocysts were more often preened by their partners than individuals with lower excretion rates. We observed that the more eggs an individual incubated and the fewer offspring fledged, the higher the rates of excreted samples containing coccidian oocysts. Our results confirm that social behaviour, physiology and parasite burden are linked in a complex and context-dependent manner. They also contribute background information supporting future conservation programmes dealing with this critically endangered species

Oxidative Stress Mediates Physiological Costs of Begging in Magpie (Pica pica) Nestlings

[Background] Theoretical models predict that a cost is necessary to guarantee honesty in begging displays given by offspring to solicit food from their parents. There is evidence for begging costs in the form of a reduced growth rate and immunocompetence. Moreover, begging implies vigorous physical activity and attentiveness, which should increase metabolism and thus the releasing of pro-oxidant substances. Consequently, we predict that soliciting offspring incur a cost in terms of oxidative stress, and growth rate and immune response (processes that generate pro-oxidants substances) are reduced in order to maintain oxidative balance. [Methodology/Principal Findings] We test whether magpie (Pica pica) nestlings incur a cost in terms of oxidative stress when experimentally forced to beg intensively, and whether oxidative balance is maintained by reducing growth rate and immune response. Our results show that begging provokes oxidative stress, and that nestlings begging for longer bouts reduce growth and immune response, thereby maintaining their oxidative status. [Conclusions/Significance] These findings help explaining the physiological link between begging and its associated growth and immunocompetence costs, which seems to be mediated by oxidative stress. Our study is a unique example of the complex relationships between the intensity of a communicative display (begging), oxidative stress, and life-history traits directly linked to viability.GM-R was supported by the Spanish Government (Ministerio de Ciencia y Tecnología, “Juan de la Cierva” program), and TR was supported by the Consejo Superior de Investigaciones Científicas (CSIC; Proyectos Intramurales Especiales)

Evolution of the mafic Villa Senni caldera-forming eruption at Colli Albani volcano, Italy, indicated by textural analysis of juvenile fragments

The Villa Senni Formation (355 ka) represents the youngest mafic caldera-forming eruption of the Colli Albani Volcano (Central Italy), and one of the best exposed large mafic ignimbrite successions on Earth. The unusual Si-undersaturated and high-K composition of the magma, and corresponding low magma viscosity, raise important questions about the conditions of magma ascent, eruption, and fragmentation that led to such a large explosive eruption. We examined the juvenile clast textures – that is, the abundance, shape, size and number density of both vesicles and leucite microlites – to reconstruct the fragmentation conditions and to trace major changes in the ascent rate and vesiculation history of the magma associated with caldera collapse. The juvenile textures record two major changes in the eruption dynamics through the stratigraphy. First, the sudden depressurization of the magma chamber and the onset of the first ignimbrite-forming phase are marked by a dramatic increase in the magma ascent velocity inferred by a decrease in vesicle and leucite microlite sizes and increase in their number densities. Second, the progressive restoration of pressure within the magma reservoir as a consequence of caldera collapse is recorded by an inversion of vesicle and leucite microlite textures, which suggest a strong decrease in magma ascent rate. Complex vent conditions in this later phase of the caldera collapse are recorded by the diversity of textural features, variation in magma chemistry and the abrupt changes in the stratigraphic record (including the presence of co-ignimbrite breccias, spatter clasts and lithics)