Heterodonty and double occlusion in <Emphasis Type="Italic">Manidens condorensis</Emphasis>: a unique adaptation in an Early Jurassic ornithischian improving masticatory efficiency

New materials of the ornithischian dinosaur Manidens condorensis highlight a strong heterodonty between the upper and lower dentitions and reveal a novel occlusion type previously unreported in herbivorous dinosaurs. The diamond-shaped maxillary teeth have prominent cingular entolophs in a V- to Z-shaped configuration that are absent in dentary teeth. These cingular entolophs bear denticles and serrations with vertical wear that is coplanar with the apical wear facets, supporting their involvement in chewing. The separated apical and basal wear in dentary teeth is consistent with the apical and cingular wear in maxillary teeth, indicating an alternate occlusion, an orthal jaw motion, and shearing interactions between marginal and cingular edges in a double occlusion. Measurements of the length and wear area along the marginal and cingular edges indicate that the latter are functionally equivalent to adding eight teeth to a maxillary toothrow of ten, almost doubling the lengths of cutting edges and the degree of intraoral processing, while maintaining a plesiomorphic skull anatomy, an adaptation to herbivory unique in Ornithischia.     

New contributions to the study of common double mutants in the human <Emphasis Type="Italic">LDL</Emphasis> receptor gene

Variations in the gene encoding the low-density lipoprotein receptor (LDLR) can cause familial hypercholesterolemia (FH), one of the most common inherited metabolic disorders in humans. The functional effects of the p.Gln92Glu and p.Asn564His alterations are predicted as benign, but the c.313 + 1G>C and p.Lys799_Phe801del changes are believed to cause disease. Although p.Gln92Glu and c.313 + 1G>C have been observed only in Spain, p.Asn564His and p.Lys799_Phe801del are widespread in Western Europe. In order to estimate the ages (t generations) of these four variants of the gene, to determine their possible origin and to consider the influence of age and selective pressure on their spread, we analyzed 86 healthy individuals and 126 FH patients in Spain. Most of the FH patients investigated carried two of these four LDLR variants simultaneously, while only one patient carried three of them simultaneously. Haplotype analyses were based on five LDLR SNPs: c.81T>C, c.1413G>A, c.1725C>T, c.1959T>C and c.2232G>A. The results suggest that p.Gln92Glu and c.313 + 1G>C arose at about the same time (99 and 103 generations ago, respectively) in the CACTG haplotype and that p.Asn564His and p.Lys799_Phe801del appeared in the CGCCG haplotype and might be slightly more recent variations (92 and 95 generations ago, respectively). Low selective pressures could explain the maintenance of these variants in spite of their ages. The origin of p.Gln92Glu and c.313 + 1G>C appears to be in Spain whereas p.Asn564His and p.Lys799_Phe801del could have been introduced in Spain by Celtic migrations in the seventh to fifth centuries BC.     

The evolution of agrarian practices and its effects on the structure of enclosure landscapes in the Alt Empordà (Catalonia,Spain), 1957–2001

During the last 50 years, mechanisation of the rural environment, and, more recently, the Common Agricultural Policy have led to profound changes in agrarian landscapes throughout Europe, and in particular in the rich and diverse Mediterranean landscapes (Meeus et al., 1990). In the north-east of the Iberian Peninsula, a small area of hedgerow landscape persists as a remnant of what was once an important centre for livestock production. This paper presents the results of a study carried out in this area with the aim of clarifying the relationship between the structural change of this hedgerow landscape and the evolution of farming practices developed by its owners and workers. It also considers these farmers’ perceptions of their pastures, of their farms and of the region. Up to 61 statistically significant relationships were found between the physical landscape characteristic variables and the socio-economical variables. Results depict a hedgerow landscape determined by the combination of two management models. Here, and contrary to conclusions reported in similar literature, traditional pasture activity leads to a weaker hedgerow network than a farming model based on crop cultivation. Management guidance required to move from the current situation towards a hedgerow landscape supporting both biodiversity and agrarian activity is discussed.     

The strength of plant-pollinator interactions

Recent studies of plant-animal mutualistic networks have assumed that interaction frequency between mutualists predicts species impacts (population-level effects), and that field estimates of interaction strength (per-interaction effects) are unnecessary. Although existing evidence supports this assumption for the effect of animals on plants, no studies have evaluated it for the reciprocal effect of plants on animals. We evaluate this assumption using data on the reproductive effects of pollinators on plants and the reciprocal reproductive effects of plants on pollinators. The magnitude of species impacts of plants on pollinators, the reciprocal impacts of pollinators on plants, and their asymmetry were well predicted by interaction frequency. However, interaction strength was a key determinant of the sign of species impacts. These results underscore the importance of quantifying interaction strength in studies of mutualistic networks. We also show that the distributions of interaction strengths and species impacts are highly skewed, with few strong and many weak interactions. This skewed distribution matches the pattern observed in food webs, suggesting that the community-wide organization of species interactions is fundamentally similar between mutualistic and antagonistic interactions. Our results have profound ecological implications, given the key role of interaction strength for community stability.     

Within-clutch egg size asymmetry covaries with embryo sex in the yellow-legged gull Larus michahellis

Non-random sex allocation may occur whenever the expected reproductive value of sons and daughters differs, as is the case when the sexes differ in susceptibility to environmental conditions or maternal effects (e.g. egg size and hatch order). Under such circumstances, covariation between egg and clutch characteristics and egg sex may be expected, and this covariation should vary with maternal state or ecological conditions. In this 2-year study (2007–2008), we examined sex allocation in relation to egg and clutch traits in the yellow-legged gull Larus michahellis, a species where male chicks are larger and more susceptible to harsh rearing conditions than female ones. In 2008, eggs were more likely male early in the season in two- but not three-egg clutches, and large eggs were more likely males late in the season. No egg/clutch traits predicted egg sex in 2007. Within-clutch egg mass asymmetry (the difference in egg mass between the first- and last-laid eggs) predicted sex in both years. In 2007, clutches with smaller egg mass variation were more likely to contain males, while in 2008 this relationship held for the last-laid egg and was reversed for the preceding egg(s). Laying order and sex of the previous egg did not predict egg sex, providing no evidence of sex-specific oocyte clustering. Thus, the relationships between egg sex and egg/clutch traits differed among years, suggesting a phenotypically plastic response of females to extrinsic conditions, and involved within-clutch egg mass asymmetry, a trait likely reflecting variation in maternal quality and/or reproductive tactics, which has been largely neglected in previous studies of sex allocation.     

A homogeneous and low-cost biosorbent for Cd,Pb and Cu removal from aqueous effluents

Heavy metal pollution of aqueous effluents is a matter of widespread concern. The use of low-cost materials for the adsorption of heavy metals seems to be a suitable choice for waste water treatment. Polyporus tenuiculus, easily cultivated on lignocellulosic waste, was assayed for Cu, Pb and Cd removal from aqueous solutions. Pb was removed more efficiently. Kinetics studies suggested a pseudo-second-order reaction and equilibrium was reached in ～ 30 min in all cases. The metal-sorption data were analysed according to several two-parameter isotherms. Data better fitted the Langmuir model for the three metals. A great dependence of metal adsorption with pH was observed. Characterisation of both the biomass and the complex metal-biomass was performed by FT-IR and SEM-EDX. Results suggest an ion exchange mechanism.     

Parent-absent signalling of need and its consequences for sibling competition in the barn swallow

In species with parental care, competition among siblings for access to limited parental resources is common. Sibling competition can be mediated by begging behaviour, a suite of different visual and acoustic displays by which offspring solicit parental care. These are mostly addressed to the parents upon food provisioning, but can also be performed in the absence of the attending parents. This so-called parent-absent begging (PAB) may function as an intrabrood communication signal and potentially affect intrabrood competition dynamics for access to food. We investigated the role of PAB in moulding sibling interactions and its effect on food intake among altricial barn swallow (Hirundo rustica) nestlings, both under normal and experimentally reduced food intake. Frequency of PAB increased after food deprivation. Nestlings that had performed PAB increased their begging intensity upon the subsequent parental feeding visit, while siblings reduced their own begging level, but only when they had not been food-deprived. As a consequence, nestlings which had performed PAB before parental arrival had larger chances of receiving food. However, nestlings did not benefit from displaying PAB when competing with food-deprived siblings. Our findings show that PAB reliably reflects need of food, indicating that a nestling will vigorously compete for the subsequent food item. By eavesdropping siblings' PAB displays, nestlings may optimally balance the costs of scrambling competition, the direct fitness gains of being fed and the indirect fitness costs of subtracting food to needy kin. However, large asymmetries in satiation between competitors may lead individual offspring to monopolize parental resources, irrespective of PAB displays.     

Great spotted cuckoo fledglings are disadvantaged by magpie host parents when reared together with magpie nestlings

The post-fledging period is a critical phase for juvenile survival, and parental care provided during this period is a key component of avian reproductive performance. Very little is known about the relationships between foster parents and fledglings of brood parasites. Here, we present the results of a 5-year study about the relationships between fledglings of the non-evictor brood parasitic great spotted cuckoo (Clamator glandarius) and its magpie (Pica pica) foster parents. Sometimes, great spotted cuckoo and magpie nestlings from the same nest can fledge successfully, but most often parasitic nestlings outcompete host nestlings and only cuckoos leave the nest. We have studied several aspects of cuckoo post-fledging performance (i.e. feeding behaviour, parental defence and fledgling survival) in experimental nests in which only cuckoos or both magpie and cuckoo nestlings survived until leaving the nest. The results indicate that great spotted cuckoo fledglings reared in mixed broods together with magpie nestlings were disadvantaged by magpie adults with respect to feeding patterns. Fledgling cuckoos reared in mixed broods were fed less frequently than those reared in only cuckoo broods, and magpie adults approached less frequently to feed cuckoos from mixed broods than cuckoos from only cuckoo broods. These results imply that the presence of host's own nestlings for comparison may be a crucial clue favouring the evolution of fledgling discrimination; and furthermore, that the risk of discrimination at the fledgling stage probably is an important selection pressure driving the evolution of the arms race between brood parasites and their hosts.     

Veterinary drugs in groundwater in a dairy region of central Argentina and risk assessment for human health

Veterinary drugs used in dairy production are potential contaminants of surface or groundwater sources, being able to affect human and environmental health. It is known that chronic exposure to antibiotics in low concentrations present in water can generate microbial resistance. This study aimed to evaluate the presence of veterinary drugs in 53 groundwater samples used for animal and human consumption, collected in dairy milking parlors, in an important milk-producing area of central Argentina, and to assess the risk to human health when they are used as drinking water. In 75% of the total samples analyzed, at least one veterinary drug was detected. The most frequently found drugs in water samples were the antibiotics tetracycline in 58.5% and oxytetracycline in 56.6%, and an anti-inflammatory, flunixin in 39.6%. In the water samples, the tetracycline and oxytetracycline concentrations were between 0.1 and 5.3 μg/L and flunixin concentrations were between 0.01 and 2.1 μg/L. The frequency of appearance and the concentration levels of the substances found in the water samples were evaluated according to the productivity, size, and production system (confined or pasture) of the dairy farms. Higher concentrations and proportions of water samples containing antibiotics were observed when the number of animals per dairy farm was >182 and when the productivity was high (>25 liters per animal per day). In the case of flunixin, the percentage of detection was similar in all evaluated categories. The risk assessment for children and adults, considering the intake of drinking water containing residues of these drugs, did not indicate a significant health risk. It would be advisable to evaluate other sources of drinking water, both surface and underground, in other regions of the country, to provide data to assess the impact of these substances and the other contaminants on environmental and human health.