Relationships among oxidative status,breeding conditions and life‐history traits in free‐living Great Tits Parus major and Common Starlings Sturnus vulgaris

The interest shown by ecologists in antioxidants and oxidative stress as potential modulators of life‐history trade‐offs has expanded greatly in recent years. However, we still know very little about natural variation in oxidative damage and antioxidant capacity in free‐living animals. In this study, we describe the natural variation in three components of oxidative balance in nestlings and breeding females in free‐living Great Tits Parus major and Common Starlings Sturnus vulgaris in central Italy, and relate these to breeding conditions and life‐history traits. Our results suggest that there are associations among oxidative physiology, reproductive activity, growth pattern and season in wild birds, but that the nature of these associations might be species‐specific rather than general across species.     

The age of the grasses and clusters of origins of C4 photosynthesis

At high temperatures and relatively low CO₂ concentrations, plants can most efficiently fix carbon to form carbohydrates through C₄ photosynthesis rather than through the ancestral and more widespread C₃ pathway. Because most C₄ plants are grasses, studies of the origin of C₄ are intimately tied to studies of the origin of the grasses. We present here a phylogeny of the grass family, based on nuclear and chloroplast genes, and calibrated with six fossils. We find that the earliest origins of C₄ likely occurred about 32 million years ago (Ma) in the Oligocene, coinciding with a reduction in global CO₂ levels. After the initial appearance of C₄ species, photosynthetic pathway changed at least 15 more times; we estimate nine total origins of C₄ from C₃ ancestors, at least two changes of C₄ subtype, and five reversals to C₃. We find a cluster of C₄ to C₃ reversals in the Early Miocene correlating with a drop in global temperatures, and a subsequent cluster of C₄ origins in the Mid‐Miocene, correlating with the rise in temperature at the Mid‐Miocene climatic optimum. In the process of dating the origins of C₄, we were also able to provide estimated times for other major events in grass evolution. We find that the common ancestor of the grasses (the crown node) originated in the upper Cretaceous. The common ancestor of maize and rice lived at 52 ± 8 Ma.     

Seed growth suppression constrains the growth of seed parasites: premature acorn abscission reduces Curculio elephas larval size

Abstract.  1. The abscission of seeds infested by insects is common in many plants and has been proposed as a defensive mechanism, although its negative consequences for insects have rarely been assessed.
2. We assessed the consequences of seed abscission studying the interactions between the holm oak Quercus ilex and the chestnut weevil Curculio elephas , its main pre-dispersal seed predator. Female weevils oviposit into the acorns and the larvae must complete their development inside a single acorn feeding on the cotyledons. The growth of the infested acorns is suppressed because they are prematurely abscised.
3. Female weevils oviposit along the acorn growing period; hence, the size of the infested acorns increased with date. The growth of the larvae inside the smaller, early infested, acorns was constrained because food (i.e. cotyledons) was frequently depleted. Larval size increased with the date along with the size of the infested acorns, but it declined slightly in the latest dates as a result of the higher conspecific competition provoked by the larger number of larvae per acorn.
4. The present results demonstrate that premature seed abscission by Q. ilex had negative consequences for C. elephas , as a smaller acorn size reduced food availability and constrained larval size, a key insect life history trait. At the same time, it is suggested that the growth suppression of infested acorns may condition the oviposition phenology of these insects according to their body size. These results need to be considered in further research in the context of the evolutionary significance of premature seed abscission as a defensive mechanism.     

Effect on Inhibition of Micromere Segregation on the Mitotic Pattern in the Sea Urchin Embryo

Detergent treatment of sea urchin eggs at the mid 4-cell stage results in prevention of micromere segregation at the fourth cleavage. In these embryos not only the formation of the primary mesenchyme is suppressed, but synchrony of cell division, which is the rule during the first four cleavage cycles, continues for several cycles after the 16-cell stage while the typical mitotic phase wave that sets in after micromere segregation is abolished.
These results support the hypothesis that micromeres act as coordinators of the mitotic activity of the embryo.     

Spring migratory routes of eight trans-Saharan passerines through the central and western Mediterranean; results from a network of insular and coastal ringing sites

Detailed information on spring migration routes of songbirds across the Mediterranean is still scanty. Results are presented here from a study on the occurrence of eight Palaearctic-African migrants across the western and central Mediterranean based on ringing data collected during the Progetto Piccole Isole, a co-ordinated project based on standardized mist netting at 21 islands and coastal stations. The species were Melodious Warbler Hippolais polyglotta , Icterine Warbler Hippolais icterina, Bonelli's Warbler Phylloscopus bonelli , Wood Warbler Phylloscopus sibilatrix , Pied Flycatcher Ficedula hypoleuca , Collared Flycatcher Ficedula albicollis , Red-backed Shrike Lanius collurio and Woodchat Shrike Lanius senator . Their capture frequencies were expressed as the frequency of each species relative to the total number of migrants ringed at each station in order to correct for differences in capture effort between stations. For most species, the detailed, quantitative results confirmed the scanty information available so far, whereas in the case of Melodious Warbler and Bonelli's Warbler, evidence of undescribed and unexpected migration routes was found. These results suggest that standardized mist netting provides an important method for studying the migratory routes of small birds, in particular for those species which are not frequently ringed in their breeding and wintering grounds.     

Activation of Satellite Cells Induced by Chronic Neostigmine Administration in the Rat

Muscle fibrillation has been suggested as a possible trigger for activation of satellite cells, a well known phenomenon associated with denervation. In order to test such a hypothesis fibrillation has been induced in normally innervated muscles by chronic administration of neostigmine and the response of satellite cells has been observed with a scanning electron microscope. The results show that satellite cells protrude from the profile of the muscle fiber, become partially separated from the latter, and align in rows. Elongated structures and presumable new muscle fibers are observed after 14 days of treatment. It is concluded that the overactivity of muscle fibers which is induced during fibrillation causes activation and differentiation of satellite cells. This result is consistent with that of a previous experiment showing that satellite cells are activated during acute increase in work-load.     

Co‐occurring increases of calcium and organellar reactive oxygen species determine differential activation of antioxidant and defense enzymes in Ulva compressa (Chlorophyta) exposed to copper excess

In order to analyse copper‐induced calcium release and (reactive oxygen species) ROS accumulation and their role in antioxidant and defense enzymes activation, the marine alga Ulva compressa was exposed to 10 µM copper for 7 d. The level of calcium, extracellular hydrogen peroxide (eHP), intracellular hydrogen peroxide (iHP) and superoxide anions (SA) as well as the activities of ascorbate peroxidase (AP), glutathione reductase (GR), glutathione‐S‐transferase (GST), phenylalanine ammonia lyase (PAL) and lipoxygenase (LOX) were determined. Calcium release showed a triphasic pattern with peaks at 2, 3 and 12 h. The second peak was coincident with increases in eHP and iHP and the third peak with the second increase of iHP. A delayed wave of SA occurred after day 3 and was not accompanied by calcium release. The accumulation of iHP and SA was mainly inhibited by organellar electron transport chains inhibitors (OETCI), whereas calcium release was inhibited by ryanodine. AP activation ceased almost completely after the use of OETCI. On the other hand, GR and GST activities were partially inhibited, whereas defense enzymes were not inhibited. In contrast, PAL and LOX were inhibited by ryanodine, whereas AP was not inhibited. Thus, copper stress induces calcium release and organellar ROS accumulation that determine the differential activation of antioxidant and defense enzymes.     

Population differences in density and resource allocation of ornamental tail feathers in the barn swallow

Many organisms show well‐defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost tail feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of tail feathers in relation to body size and wing size. Tail feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer tails. The extra enlargement of the tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying feather structure to produce longer feathers of lower density. These two separate processes accounting for the production of longer and more costly tail feathers and less dense feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 925–936.     

Hydrogen cyanide release during feeding of generalist and specialist lepidopteran larvae on a cyanogenic plant, Passiflora capsularis

Abstract.  The hydrogen cyanide-based interaction of a strongly cyanogenic plant, Passiflora capsularis , and larvae of two insect herbivores, a generalist ( Spodoptera frugiperda ) and a specialist ( Heliconius erato ), is examined in terms of the combined kinetics of the feeding process and the simultaneous hydrogen cyanide (HCN) liberation, as compared with the natural kinetics of hydrogen cyanide evolution by plant-leaf tissue. There are marked differences in acceptance of P. capsularis by third-instar larvae of specialist and generalist species. The former, H. erato , display a parsimonious ingestion rate of 0.74 ± 0.15 mg (fresh weight) min⁻¹ comprising 18% active feeding time, whereas S. frugiperda larvae show a more erratic and restrained feeding involving 4% of the time at 0.45 ± 0.14 mg min⁻¹. These S. frugiperda larvae ingest 124.4 ± 8.3 mg (fw) of the non-cyanogeneic Spinacia oleracea leaves in 24 h compared with only 74.7 ± 20.1 mg of P. capsularis in the same period. The total hydrogen cyanide released naturally from wild specimens of P. capsularis plants is in the range 326–3901 μg g⁻¹. Hydrogen cyanide evolution from macerated P. capsularis leaves takes place along a hyperbolic function with time and initial velocities of cyanide evolution are a linear function of total hydrogen cyanide. When feeding on P. capsularis leaves, H. erato releases only a minor fraction relative to total hydrogen cyanide (0.09%) and to the anticipated cyanide from the initial velocity (7%). By contrast, S. frugiperda evokes 5.8-fold more than the anticipated hydrogen cyanide release from the plant. The findings are interpreted as diverging strategies by generalist and specialist insects in the utilization of hydrogen cyanide in cyanogenic plants.