Light and Electron Microscope Study of Dunaliella primolecta Butcher (Volvocida)*

SYNOPSIS. Light and electron microscope observations on Dunaliella primolecta Butcher from logarithmic and stationary phases of batch cultures are correlated. Except for the lack of a cell wall the fine structure has typical volvocid features. The transition from logarithmic to stationary phase is marked by changes in content and size of cytoplasmic vacuoles, accumulation of cytoplasmic lipid, accumulation of starch in the plastid matrix, and by the formation of autophagosome-like bodies. The organelles in stationary-phase flagellates are closely packed together because of the cytoplasmic lipid and starch-distended chloroplast. Organisms from logarithmic phase have an abundant ribosome-packed groundplasm supporting the organelles. In the cytochemical demonstration of acid phosphatase activity, Golgi cisternae and smooth and coated Golgi vesicles contain Gomori reaction product. The possible roles of the Golgi apparatus in this flagellate are discussed.     

Anti-mosquito antibodies decrease the reproductive capacity of Aedes aegypti

Aedes aegypti (L.) fed on rabbits immunized with mosquito antigens showed a reduction in fecundity in the first oviposition and decreased viability of the progeny. Feeding behaviour of mosquitoes was not affected and no significant mortality was observed due to the presence of anti-mosquito antibodies in the bloodmeal. Antibodies were detected in the oocytes of mosquitoes 48 h after the bloodmeal. The role of specific antibodies in influencing fecundity is discussed.     

A taxonomic and horticultural review of Erythronium L. (Liliaceae)

MATHEW, B., 1992. A review of Erythronium L. (Liliaceae). The morphology, distribution and horticultural value of the genus is reviewed and a tentative key to the identification of the species is provided.     

Stereological Studies of the Effects of α-MSH and cAMP on Melanosomes in Melanoma Cells

The effects of α-MSH and cAMP on melanosomes in Cloudman S91 melanoma cells were investigated by modern stereological techniques. Cells were cultured for 4 days in medium containing α-MSH or cAMP harvested at 24 hour intervals; some were frozen for melanin assay and the reminder embedded in Epon for light and electron microscopy. Cellular and melanosomal parameters were estimated by new stereological probes. We found that both stimulators induced increases in nuclear volume, cell volume, and the volume fractions and volumes of premelanosomes (V_Vpm,cell’V_pm) and mature melanosomes (V_Vmm,cell’V_mm) and the number of mature melanosomes (N_mm). Both stimulators also caused declines in the volume of individual mature melanosomes (_Vimm) the melanin content per mature melanosome unit volume and the melanin content per individual mature melanosome. The increases in the volume of individual premelanosomes and the number of premelanosomes were only induced by cAME The effect cAMP on some parameters occurred 24 hours prior to α-MSH and was more marked. The response of premelanosomes to the stimulators was more sensitive than mature melanosomes. These results suggest that both stimulators enchanced melanogenesis by increasing the V_Vpm,cell’V_Vmm,cell’V_pm, V_mm and N_mm. The melanogenic level did not depend on the _Vimm and melanin concentration in melanosomes. The maturation of premelanosomes was involved in melanogenesis induced by both stimulators, but, de novo synthesis and enlargement of premelanosomes were only stimulated by cAME It imply that exogenous cAMP may affect melanosomes, and hence melanogenesis in quantitatively or qualitatively different ways to α-MSH.     

Adaptive differences in plant physiology and ecosystem paradoxes: insights from metabolic scaling theory

The link between variation in species‐specific plant traits, larger scale patterns of productivity, and other ecosystem processes is an important focus for global change research. Understanding such linkages requires synthesis of evolutionary, biogeograpahic, and biogeochemical approaches to ecological research. Recent observations reveal several apparently paradoxical patterns across ecosystems. When compared with warmer low latitudes, ecosystems from cold northerly latitudes are described by (1) a greater temperature normalized instantaneous flux of CO₂ and energy; and (2) similar annual values of gross primary production (GPP), and possibly net primary production. Recently, several authors attributed constancy in GPP to historical and abiotic factors. Here, we show that metabolic scaling theory can be used to provide an alternative ‘biotically driven’ hypothesis. The model provides a baseline for understanding how potentially adaptive variation in plant size and traits associated with metabolism and biomass production in differing biomes can influence whole‐ecosystem processes. The implication is that one cannot extrapolate leaf/lab/forest level functional responses to the globe without considering evolutionary and geographic variation in traits associated with metabolism. We test one key implication of this model – that directional and adaptive changes in metabolic and stoichiometric traits of autotrophs may mediate patterns of plant growth across broad temperature gradients. In support of our model, on average, mass‐corrected whole‐plant growth rates are not related to differences in growing season temperature or latitude. Further, we show how these changes in autotrophic physiology and nutrient content across gradients may have important implications for understanding: (i) the origin of paradoxical ecosystem behavior; (ii) the potential efficiency of whole‐ecosystem carbon dynamics as measured by the quotient of system capacities for respiration, R, and assimilation, A; and (iii) the origin of several ‘ecosystem constants’– attributes of ecological systems that apparently do not vary with temperature (and thus with latitude). Together, these results highlight the potential critical importance of community ecology and functional evolutionary/physiological ecology for understanding the role of the biosphere within the integrated earth system.     

Growth patterns of a stream vertebrate differ between urban and forested catchments

1. Urban development results in the decline of amphibian density and species richness. A logical next step towards understanding why urbanisation negatively impacts amphibians is to track species‐specific demographic responses to urbanisation. 2. We monitored growth of two‐lined salamander (Eurycea cirrigera Green) larvae over two complete cohorts (2006 and 2007) in nine western Georgia, U.S.A. streams. 3. We found that salamanders in streams surrounded by urbanised and developing catchments hatched at the same size as their reference‐stream counterparts, but achieved larger sizes within the first few months of growth. We evaluated the effect of four variables that correlate with the urban‐forest gradient and found that elevated temperatures in the urban environment, coupled with decreased intraspecific competition because of lower survivorship in these same habitats, were two of the most likely explanations for increased growth rates. 4. Such an increase in growth of surviving larvae may maintain population viability in urban areas where it has been shown survival is difficult because of increased in‐channel flow during flood events. Because larvae that do survive in urban streams undergo metamorphosis at large sizes, they may recoup a component of fitness (i.e. increased adult survivorship and reproduction) through growth.     

Condensed Tannins' Effect on White-Tailed Deer Forage Digestibility in Mississippi

Abstract: Condensed tannins (CT) can reduce digestibility of forages for white-tailed deer (Odocoileus virginianus), potentially confounding estimates of diet quality and nutritional carrying capacity. We collected 143 spring and 142 summer samples of 8 important deer forage species from 22 properties in Mississippi, USA, and tested for CT content using a modified butanol-HCl assay. Three species (partridge pea [Chamaecrista fasciculata], southern dewberry [Rubus trivialis], and roundleaf greenbrier [Smilax rotundifolia]) contained CT, ranging from 0.11% to 6.46% dry weight. Summer CT concentration was greater than in spring for 2 species. We ranked soil samples from least to most fertile using 8 chemical characteristics and found a positive correlation between fertility and CT concentration for 1 species and no correlation for 2 species. We tested effects of CT concentration on in vitro dry matter disappearance (IVDMD) and in vitro protein digestibility using samples of partridge pea and roundleaf greenbrier and rumen fluid from 3 free-ranging deer. Average IVDMD was reduced 1.9% for each 1% increase in CT concentration. In vitro protein digestibility was reduced 2.5% for each 1% increase in CT concentration. Assuming that our methods reflect the effects of CT on in vivo digestibility, maximum loss of available crude protein (CP) in our samples was 3.0 g/100 g dry-weight forage, and only 13 of the 112 CT-containing forage samples (12%) would have decreased available CP by >1 g/100 g dry-weight forage. Deer consuming equal portions of sampled forages would lose <1% of dietary CP to CT. Comparisons of foraging area quality using crude protein estimates should be unaffected by CT under reasonable restrictions of similar habitat types, soil fertility, and time. Given the ability of deer to forage selectively and the abundance of alternative forages in Mississippi, the potential for CT to substantially affect spring or summer diet quality of deer appears minimal.     

Skolithos pipe rock and associated ichnofabrics from the southern Rocky Mountains,Canada: colonization trends and environmental controls in an early Cambrian sand‐sheet complex

Desjardins, P.R., Mángano, M.G., Buatois, L.A. & Pratt, B.R. 2010: Skolithos pipe rock and associated ichnofabrics from the southern Rocky Mountains, Canada: colonization trends and environmental controls in an early Cambrian sand‐sheet complex. Lethaia, 10.1111/j.1502‐3931.2009.00214.x The Lower Cambrian Gog Group of the southern Rocky Mountains of western Canada offers an opportunity to explore animal–sediment relationships in a high‐energy setting, during the early phase of Phanerozoic diversification. Its strata record a sand‐sheet complex on the broad pericontinental shelf of West Laurentia. Six ichnofabrics are recognized: Skolithos IF‐1 characterized by Skolithos linearis in planar cross‐stratified sandstone; Skolithos IF‐2 with Skolithos linearis and accessory Diplocraterion parallelum in ripple cross‐laminated, and planar and trough cross‐stratified sandstone; Skolithos IF‐3 with S. linearis and Planolites montanus in wavy‐ and flaser‐bedded sandstone, interfingering with bioturbated mudstone exhibiting P. montanus and Teichichnus rectus; Skolithos IF‐4, characterized by abundant Skolithos linearis in planar and trough cross‐stratified sandstone; Rosselia IF‐1 consisting of Rosselia isp. in planar cross‐stratified sandstone; and Rosselia IF‐2 consisting of scattered small Rosselia isp. in hummocky, cross‐stratified sandstone. The presence of contrasting ichnofabrics within a single early Cambrian sand‐sheet complex illuminates how the colonization trends of suspension and detritus feeders were controlled by factors specific to the various sub‐environments. □Gog Group, Ichnofabric, Lower Cambrian, Pipe Rock, Rosselia, Skolithos.     

The bee‐killing flies,genus Melaloncha Brues (Diptera: Phoridae): a combined molecular and morphological phylogeny

The phylogeny of the bee‐killing flies, genus Melaloncha Brues (Diptera: Phoridae) is analysed using six genes –cytochrome oxidase I, 16S ribosomal DNA, 12S ribosomal DNA, NADH1 dehydrogenase, 28S ribosomal DNA and CAD– plus 47 morphological characters. A total of 91 specimens, including eight out‐groups and 83 Melaloncha (representing 70 species) were included in the analyses. Parsimony analysis of the combined data set produced a single most parsimonious tree with varied Bremer and bootstrap support of interior nodes. Bayesian analysis of molecules only and of morphology + molecules produced trees largely in agreement with parsimony results, although with a few differences. Supported groups included subfamily Metopininae, genus Melaloncha, and subgenera Melaloncha s.s. and Melaloncha (Udamochiras) Enderlein. Within the subgenera, the previously recognized Melaloncha furcata, Melaloncha cingulata, Melaloncha ungulata and Melaloncha stylata groups were recovered, as well as some new groupings. The M. furcata group was placed as the sister group of other Melaloncha s.s., which is consistent with known host‐attacking behaviour.