Activity and Compartmentation of Photosynthetic Carboxylases in Normal and Chloroplast-mutant Maize Leaves

The activity of ribulose-l,5-diphosphate carboxylase (RudiP-carboxylase) and phosphoenolpyruvate carboxylase (PEP-carboxylase) measured in vitro was independent from the chlorophyll content of the leaves. The relatively high activity of PEP-carboxylase as compared to the RudiP-carboxylase activity was particularly pronounced in the mutants. Realization of the potential (in vitro measured) carboxylating activities in fixation of CO₂in vivo was practically complete in normal leaves. In the mutants, however, CO₂ fixation was lower than the level permitted by the carboxylase activity. This could be explained only in part by the impaired rate of photophosphorylation. Compartmentation of PEP-carboxylase was different in normal and mutant leaves: in contrast to the normal ones, parenchyma-sheath cells of the mutants exhibited high PEP-carboxylase activity. Competition of PEP-carboxylase with RudiP-carboxylase for CO₂ in the mutants led to accumulation of organic acids, and can account for their low photosynthetic activity.     

Feeding and Resting Postures of Wild Northern Muriquis (Brachyteles hypoxanthus)

Increased body size in Brachyteles has been regarded as an important evolutionary adaptation that allowed a greater reliance on leaves compared to other more frugivorous Atelidae, but its association with muriqui positional behavior and substrate use is still unknown. Here, we present original data on the feeding and resting postures of the northern muriqui (Brachyteles hypoxanthus) and evaluate predictions about the relationships between body size, postural behavior, and substrate use derived from previously published data for other atelids (e.g. Alouatta, Ateles, and Lagothrix). The study was undertaken from August 2002 to July 2003 on a large group of well‐habituated muriquis inhabiting the Reserva Particular do Patrimônio Natural – Felíciano Miguel Abdala in Minas Gerais, Brazil. Consistent with our predictions, we found that B. hypoxanthus was highly suspensory during postural feeding (60.9%) and commonly used tail–hind limb suspension/horizontal tripod (38.0%) or tail–forelimb/hind limb suspension (21.4%). However, although tail‐suspensory postures permitted the muriquis to use the terminal canopy and small‐sized substrates, these areas were also accessed via tail‐assisted above‐branch postural behaviors involving multiple substrates. Unexpectedly, tail‐suspensory postures were found to be frequently associated with large substrates, tree trunks, and the understory. We suggest that Brachyteles’ ability to access food resources from all areas of a feeding tree and from tree crowns at different canopy levels may account for their ability to efficiently exploit food resources in seasonal disturbed forest fragments of the Brazilian Atlantic Forest today. Am. J. Primatol. 75:74‐87, 2013. © 2012 Wiley Periodicals, Inc.     

Callus Initiation and Organized Development from Zamia pumila Embryo Explants

Explants derived from Zamia pumila embryos were cultured ona Murashige and Skoog basal medium supplemented with naphthaleneaceticacid (NAA), N⁴-benzylaminopurine (BAP), or combinations of thetwo at 27 °C in darkness. NAA was invariably required forcallus initiation, and its minimal effective concentration was0.1 mg l^–1. BAP was not always required, and dependingon the explant type and NAA concentration, BAP either enhanced,suppressed, or had little effect on the frequency of callusinitiation. High frequency of callus initiation occurred with1.0 mg l^–1 NAA combined with 0.01 or 1.0 mg l^–1BAP. When the concentration of NAA was high relative to thatof BAP, friable callus was produced. As the relative BAP concentrationwas increased, a more compact callus formed. Compact-nodularcallus developed at equal concentrations of NAA and BAP overa wide range of absolute concentrations. Friable callus formedroots only. Compact-nodular callus formed roots, shoots andembryo-like structures. Root and shoot formation predominatedand were of nearly equal frequency. Formation of embryo-likestructures was infrequent. Zamia pumila, callus differentiation, callus formation, embryo culture, naphthaleneacetic acid, N⁴-benzylaminopurine     

Nucleolus size varies with sex,ploidy and gene dosage in insects

The nucleolus constitutes a cytologically visible phenotype for ribosomal DNA (rDNA). Nucleolar size, as determined by silver staining, is a good indicator of cell proliferation rate and biosynthetic activity. Nevertheless, the relationship between rDNA content and sexual dimorphism for nucleolar size is not well documented. In the present study, the impact of sex and ploidy level on nucleolar size is investigated in three haplo/diploid and three diplo/diploid species of insect. Nucleolar sizes are found to be proportional to ploidy level in the haplo/diploid hymenopterans Trypoxylon albitarse and Nasonia vitripennis. Conversely, in the ant Messor barbarus, nucleolar sizes are larger in haploid males (winged) than diploid females (apterous). Among the diplo/diploid species, evidence for gene dosage compensation on nucleolar activity is suggested by the absence of sex differences in Drosophila simulans, a species in which rDNA is limited to the X chromosome. By contrast, in the grasshopper Stenobothrus festivus, another species with rRNA genes restricted to the X chromosome, the size of the nucleolus is significantly larger in females than in males. Additionally, in the grasshopper Chorthippus parallelus, where rDNA is distributed evenly on several autosomes of males and females, the females also show larger nucleoli than males. In both grasshopper species, the magnitude of the female/male ratio for nucleolus area is very similar to the body size ratio, suggesting that body size, as well as sex, ploidy, gene dosage and physiological activity, may be an important determinant of nucleolus area.     

Ecological assessment of an intermittent Mediterranean river using community structure and function: evaluating the role of different organism groups

1. Reliable lotic ecological monitoring requires knowledge of river typology, environmental factors, the effect of stressors known here as ‘pressures’ and appropriate indicators of anthropogenically induced change. We sampled benthic macroinvertebrate, fish, bird and macrophyte communities along an intermittent Mediterranean river and analysed community structure (relative abundance) and function (metrics) relative to environmental and pressure gradients in order to identify suitable indicator group(s) for future monitoring and mitigation programmes. 2. Principal components analysis revealed that scale‐dependent longitudinal differences in valley form separated narrower higher lying sites and tributaries with good quality habitats from more open degraded sites lower down the river continuum on a small floodplain and large scale pressures describing changes in land use related to agriculture with associated physical bankside and channel impacts. 3. Forward selection of variables in redundancy analysis (RDA) showed that reach scale environmental variables were selected more frequently than pressure variables for each organism group. Altitude and pH were highly redundant within and between groups, indicating essentially longitudinal structural and functional distribution patterns. Redundancy was far lower between selected pressure variables, but single or no pressure variables were retained for some organism groups indicating poor association of functional data, in particular, with the identified pressures. All RDA results indicated a longitudinal pH gradient, highlighting the combined effect of multiple environmental and pressure based mechanisms on organism groups. 4. Large, mobile organisms such as fish and birds provided a reliable link between organism structure and function, environmental factors and physical disturbance of the channel, bankside and wider river corridor. Benthic macroinvertebrate and macrophyte structural data revealed distribution patterns in relation to water velocity, a key parameter for developing appropriate compensation measures. 5. Results clearly show the importance of assessing patterns of both functional and structural change across multiple organism groups in order to identify typologically appropriate links with complex environmental and pressure gradients and develop and implement appropriate monitoring systems.     

Comparison of two sampling methods for domestic populations of Triatoma infestans in north-west Argentina

Abstract. In mud-and-thatch houses of Santiago del Estero Province, northwest Argentina, where no insecticides had been sprayed officially to control domestic infestations of the Chagas disease vector Triatoma infestans (Klug) (Hemiptera: Reduviidae), two knockdown (KD) insecticidal collection procedures were compared with the standard flush-out (FO) method for sampling T. infestans. Bugs were collected by FO using 0.2% tetramethrin in bedrooms of (1) 41 houses of Amama village employing 1 man-hour of capture effort per house, and (2) 19 houses of Trinidad and Mercedes villages employing 4 man-hours/house. From the same houses, 2-5 days after the manual FO collection, bugs were collected by KD indoor-spraying of deltamethrin 25mga.i./m² in Amama, or burning of one γ-HCH (=γ-BHC) fumigant tablet 3.1g of γ-isomer) per bedroom in Trinidad and Mercedes. The majority of infestations were detected by both methods, the proportion of positive houses being 81% at Amama and 95% at the other villages. Although the FO method was more sensitive, at least because it was applied first, the KD method detected infestations in 25% of houses where bugs were not found by FO. Bug densities estimated by FO or by subsequent KD in each house were significantly correlated: r = 0.795 for deltamethrin; r= 0.882 for y-HCH. Compared with FO collections of T.infestans large stages, i.e. adults plus fourth and fifth instar nymphs, the KD catch averaged 0.88x with deltamethrin and 0.57× with γ-HCH, regardless of the apparent population density of bugs per house. However, the KD method has practical advantages of speed and standardization.